bims-proarb 2021-07-18 papers

bims-proarb

Biomed News

on Proteostasis in aging and regenerative biology

Issue of 2021–07–18
forty papers selected by
Rich Giadone, Harvard University

Transcription factors and chaperone proteins play a role in launching a faster response to heat stress and aggregation.
The diverse functions of small heat shock proteins in the proteostasis network.
Excessive endoplasmic reticulum stress drives aberrant mouse trophoblast differentiation and placental development leading to pregnancy loss.
In vivo two-photon microscopy protocol for imaging microglial responses and spine elimination at sites of fibrinogen deposition in mouse brain.
Proteasome activity contributes to pro-survival response upon mild mitochondrial stress in Caenorhabditis elegans.
Direct visualization and profiling of protein misfolding and aggregation in live cells.
Combinatorial Approach Using Caenorhabditis elegans and Mammalian Systems for Aging Research.
Differential Analysis of N-glycopeptide Abundance and N-glycosylation Site Occupancy for Studying Protein N-glycosylation Dysregulation in Human Disease.
A role for the ribosome-associated complex in activation of the IRE1 branch of UPR.
Regulation of muscle and mitochondrial health by the mitochondrial fission protein Drp1 in aged mice.
The Neurogenic Niche in Alzheimer's disease.
Adult Hippocampal Neurogenesis and Alzheimer's Disease: Novel Application of Mesenchymal Stem Cells and their Role in Hippocampal Neurogenesis.
Inhibition of heat shock proteins increases autophagosome formation, and reduces the expression of APP, Tau, SOD1 G93A and TDP-43.
The protein inputs of an ultra-predictive aging clock represent viable anti-aging drug targets.
Autophagosome Trafficking.
Heat shock protein 20 promotes sirtuin 1-dependent cell proliferation in induced pluripotent stem cells.
At elevated temperatures, heat shock protein genes show altered ratios of different RNAs and expression of new RNAs, including several novel HSPB1 mRNAs encoding HSP27 protein isoforms.
The mechanisms of vascular aging.
Alpha-Synuclein Post-translational Modifications: Implications for Pathogenesis of Lewy Body Disorders.
Age-dependent alterations in key components of the nigrostriatal dopaminergic system and distinct motor phenotypes.
Protein disulfide isomerase inhibits endoplasmic reticulum stress response and apoptosis via its oxidoreductase activity in colorectal cancer.
Luteolin alleviates cognitive impairment in Alzheimer's disease mouse model via inhibiting endoplasmic reticulum stress-dependent neuroinflammation.
Hippo signaling: A stress response pathway in stem cells.
Analysis of Age-Related Circular RNA Expression Profiles in Mesenchymal Stem Cells of Rat Bone Marrow.
Translational control of stem cell function.
Chemical Autophagy Regulators.
Knock-in models related to Alzheimer's disease: synaptic transmission, plaques and the role of microglia.
An mTORC1-GRASP55 signaling axis controls unconventional secretion to reshape the extracellular proteome upon stress.
PIP2 depletion and altered endocytosis caused by expression of Alzheimer's disease-protective variant PLCγ2 R522.
Improved correction of F508del-CFTR biogenesis with a folding facilitator and an inhibitor of protein ubiquitination.
The role of Ire1 in Drosophila eye pigmentation revealed by an RNase dead allele.
A protective signal between the brain's supporting cells in Alzheimer's disease.
Role of autophagy in midgut stem cells of silkworm Bombyx mori, during larval-pupal metamorphosis.
Exogenous misfolded protein oligomers can cross the intestinal barrier and cause a disease phenotype in C. elegans.
The role of mTORC1 activation in seizure-induced exacerbation of Alzheimer's disease.
Distinct states of proinsulin misfolding in MIDY.
Site-specific O-GlcNAcylation of Psme3 maintains mouse stem cell pluripotency by impairing P-body homeostasis.
Citrus alkaline extracts prevent endoplasmic reticulum stress in type II alveolar epithelial cells to ameliorate pulmonary fibrosis via the ATF3/PINK1 pathway.
Olfaction as an early marker of Parkinson's disease and Alzheimer's disease.
A new model for sensitive detection of zoonotic prions by PrP transgenic Drosophila.

Comput Biol Chem. 2021 Jun 24. pii: S1476-9271(21)00101-8. [Epub ahead of print]93 107534

Transcription factors and chaperone proteins play a role in launching a faster response to heat stress and aggregation.

Sushmita Pal, Rati Sharma.

  Proteins, under conditions of cellular stress, typically tend to unfold and form lethal aggregates leading to neurological diseases like Parkinson's and Alzheimer's. A clear understanding of the conditions that favor dis-aggregation and restore the cell to its healthy state after they have been stressed is therefore important in dealing with these diseases. The heat shock response (HSR) mechanism is a signaling network that deals with these undue protein aggregates and aids in the maintenance of homeostasis within a cell. This framework, on its own, is a mathematically well studied mechanism. However, not much is known about how the various intermediate mis-folded protein states of the aggregation process interact with some of the key components of the HSR pathway such as the Heat Shock Protein (HSP), the Heat Shock Transcription Factor (HSF) and the HSP-HSF complex. In this article, using kinetic parameters from the literature, we propose and analyze two mathematical models for HSR that also include explicit reactions for the formation of protein aggregates. Deterministic analysis and stochastic simulations of these models show that the folded proteins and the misfolded aggregates exhibit bistability in a certain region of the parameter space. Further, the models also highlight the role of HSF and the HSF-HSP complex in reducing the time lag of response to stress and in re-folding all the mis-folded proteins back to their native state. These models, therefore, call attention to the significance of studying related pathways such as the HSR and the protein aggregation and re-folding process in conjunction with each other.

Keywords:  Heat shock response; Mathematical model; Protein aggregation; Sensitivity analysis; Stochastic simulations

DOI:  https://doi.org/10.1016/j.compbiolchem.2021.107534
J Mol Biol. 2021 Jul 14. pii: S0022-2836(21)00386-7. [Epub ahead of print] 167157

The diverse functions of small heat shock proteins in the proteostasis network.

Kevin Reinle, Axel Mogk, Bernd Bukau.

  The protein quality control (PQC) system maintains protein homeostasis by counteracting the accumulation of misfolded protein conformers. Substrate degradation and refolding activities executed by ATP-dependent proteases and chaperones constitute major strategies of the proteostasis network. Small heat shock proteins represent ATP-independent chaperones that bind to misfolded proteins, preventing their uncontrolled aggregation. sHsps share the conserved α-crystallin domain (ACD) and gain functional specificity through variable and largely disordered N- and C-terminal extensions (NTE, CTE). They form large, polydisperse oligomers through multiple, weak interactions between NTE/CTEs and ACD dimers. Sequence variations of sHsps and the large variability of sHsp oligomers enable sHsps to fulfill diverse tasks in the PQC network. sHsp oligomers represent inactive yet dynamic resting states that are rapidly deoligomerized and activated upon stress conditions, releasing substrate binding sites in NTEs and ACDs Bound substrates are usually isolated in large sHsp/substrate complexes. This sequestration activity of sHsps represents a third strategy of the proteostasis network. Substrate sequestration reduces the burden for other PQC components during immediate and persistent stress conditions. Sequestered substrates can be released and directed towards refolding pathways by ATP-dependent Hsp70/Hsp100 chaperones or sorted for degradation by autophagic pathways. sHsps can also maintain the dynamic state of phase-separated stress granules (SGs), which store mRNA and translation factors, by reducing the accumulation of misfolded proteins inside SGs and preventing unfolding of SG components. This ensures SG disassembly and regain of translational capacity during recovery periods.

Keywords:  chaperone; protein aggregation; proteostasis; small heat shock protein; stress granule

DOI:  https://doi.org/10.1016/j.jmb.2021.167157
J Physiol. 2021 Jul 16.

Excessive endoplasmic reticulum stress drives aberrant mouse trophoblast differentiation and placental development leading to pregnancy loss.

Nadejda Capatina, Myriam Hemberger, Graham J Burton, Erica D Watson, Hong Wa Yung.

  Endoplasmic reticulum (ER) stress promotes placental dysmorphogenesis and is associated with poor pregnancy outcomes. We show that unfolded protein response signalling pathways located in the ER drive differentiation of mouse trophoblast stem cells into trophoblast subtypes involved in development of the placental labyrinth zone and trophoblast invasion. In a mouse model of chronic ER stress (Eif2s1tm1RjK ), higher ER stress in homozygous blastocysts is accompanied by reduced trophectoderm cell number, developmental delay, and is associated with an increased incidence of early pregnancy loss. Administration of the chemical chaperone, tauroursodeoxycholic acid, to Eif2s1tm1RjK heterozygous females during pregnancy alleviated ER stress in the mutant placenta, restored normal trophoblast populations and reduced the frequency of early pregnancy loss. Our results suggest that alleviation of intrauterine ER stress could provide a potential therapeutic target to improve pregnancy outcome in women with pre-gestational metabolic or gynaecologic conditions. ABSTRACT: Women with pre-gestational health conditions (e.g., obesity, diabetes) or gynaecological problems (e.g., endometriosis) are at increased risk of adverse pregnancy outcomes including miscarriage, preeclampsia and fetal growth restriction. Increasing evidence suggests that unfavourable intrauterine conditions leading to poor implantation and/or defective placentation are a possible causative factor. The endoplasmic reticulum (ER) unfolded protein response (UPRER ) signalling pathways are a convergence point of various physiological stress stimuli that can be triggered by an unfavourable intrauterine environment. Therefore, we explored the impact of ER stress on mouse trophoblast differentiation in vitro, mouse blastocyst formation and early placenta development in the Eif2s1tm1RjK mutant mouse model of chronic ER stress. Chemically-manipulated ER stress or activation of UPRER pathways in a mouse trophoblast stem cell line promoted lineage-specific differentiation. Co-treatment with specific UPRER pathway inhibitors rescued this effect. While the inner cell mass was unaffected, the trophectoderm of homozygous Eif2s1tm1RjK blastocysts exhibited ER stress associated with a reduced cell number. Furthermore, one-third of Eif2s1tmRjK homozygous blastocysts exhibited severe developmental defects. We have previously reported a reduced trophoblast population and premature trophoblast differentiation in Eif2s1tm1RjK homozygous placentas at mid-gestation. Here, we demonstrate that treatment of Eif2s1+/tm1RjK heterozygous pregnant females with the chemical chaperone tauroursodeoxycholic acid alleviated ER stress, restored the trophoblast population, and reduced the frequency of embryonic lethality. Our data suggest that therapeutic targeting of ER stress may improve pregnancy outcome in women with pre-gestational metabolic or gynaecologic conditions. This article is protected by copyright. All rights reserved.

Keywords:  Endoplasmic reticulum stress; Placental development; Pregnancy complications; Trophoblast differentiation

DOI:  https://doi.org/10.1113/JP281994
STAR Protoc. 2021 Sep 17. 2(3): 100638

In vivo two-photon microscopy protocol for imaging microglial responses and spine elimination at sites of fibrinogen deposition in mouse brain.

Reshmi Tognatta, Mario Merlini, Zhaoqi Yan, Renaud Schuck, Dimitrios Davalos, Katerina Akassoglou.

  Deposition of the blood coagulation factor fibrinogen in the central nervous system is a hallmark of neurological diseases with blood-brain barrier disruption. We describe in vivo two-photon imaging of microglial responses and neuronal spine elimination to either intracortical microinjection of fibrinogen in healthy mice or to endogenously labeled fibrinogen deposits in Alzheimer's disease mice. This protocol allows the longitudinal study of glial and neuronal responses to blood proteins and can be used to test drug efficacy at the neurovascular interface. For complete details on the use and execution of this protocol, please refer to Davalos et al. (2012), Ryu et al. (2018), and Merlini et al. (2019).

Keywords:  Immunology; Microscopy; Model Organisms; Neuroscience

DOI:  https://doi.org/10.1016/j.xpro.2021.100638
PLoS Biol. 2021 Jul;19(7): e3001302

Proteasome activity contributes to pro-survival response upon mild mitochondrial stress in Caenorhabditis elegans.

Maria Sladowska, Michał Turek, Min-Ji Kim, Krzysztof Drabikowski, Ben Hur Marins Mussulini, Karthik Mohanraj, Remigiusz A Serwa, Ulrike Topf, Agnieszka Chacinska.

Defects in mitochondrial function activate compensatory responses in the cell. Mitochondrial stress that is caused by unfolded proteins inside the organelle induces a transcriptional response (termed the "mitochondrial unfolded protein response" [UPRmt]) that is mediated by activating transcription factor associated with stress 1 (ATFS-1). The UPRmt increases mitochondrial protein quality control. Mitochondrial dysfunction frequently causes defects in the import of proteins, resulting in the accumulation of mitochondrial proteins outside the organelle. In yeast, cells respond to mistargeted mitochondrial proteins by increasing activity of the proteasome in the cytosol (termed the "unfolded protein response activated by mistargeting of proteins" [UPRam]). The presence and relevance of this response in higher eukaryotes is unclear. Here, we demonstrate that defects in mitochondrial protein import in Caenorhabditis elegans lead to proteasome activation and life span extension. Both proteasome activation and life span prolongation partially depend on ATFS-1, despite its lack of influence on proteasomal gene transcription. Importantly, life span prolongation depends on the fully assembled proteasome. Our data provide a link between mitochondrial dysfunction and proteasomal activity and demonstrate its direct relevance to mechanisms that promote longevity.

DOI: https://doi.org/10.1371/journal.pbio.3001302
Curr Opin Chem Biol. 2021 Jul 08. pii: S1367-5931(21)00075-2. [Epub ahead of print]64 116-123

Direct visualization and profiling of protein misfolding and aggregation in live cells.

Sicheng Tang, Wenting Wang, Xin Zhang.

  Over the past few years, research tools have been developed to monitor the multistep protein aggregation process in live cells, a process that has been associated with a growing number of human diseases. Herein, we describe recent advances in methods that can either survey the distribution of aggregation at the level of the cellular proteome using mass spectroscopy or discern the multistep aggregation process of specific proteins of interest via fluorescence signals. Future development and application of such technologies are expected to provide insights on mechanisms, diagnosis, and treatment of diseases rooted in protein aggregation.

Keywords:  Biosensor; Fluorescence microscopy; Mass spectrometry; Protein aggregation

DOI:  https://doi.org/10.1016/j.cbpa.2021.05.008
Mol Cells. 2021 Jul 12.

Combinatorial Approach Using Caenorhabditis elegans and Mammalian Systems for Aging Research.

Gee-Yoon Lee, Jooyeon Sohn, Seung-Jae V Lee.

  Aging is associated with functional and structural declines in organisms over time. Organisms as diverse as the nematode Caenorhabditis elegans and mammals share signaling pathways that regulate aging and lifespan. In this review, we discuss recent combinatorial approach to aging research employing C. elegans and mammalian systems that have contributed to our understanding of evolutionarily conserved aging-regulating pathways. The topics covered here include insulin/IGF-1, mechanistic target of rapamycin (mTOR), and sirtuin signaling pathways; dietary restriction; autophagy; mitochondria; and the nervous system. A combinatorial approach employing high-throughput, rapid C. elegans systems, and human model mammalian systems is likely to continue providing mechanistic insights into aging biology and will help develop therapeutics against age-associated disorders.

Keywords:  Caenorhabditis elegans; aging; combinatorial approach; lifespan; mammal

DOI:  https://doi.org/10.14348/molcells.2021.0080
Bio Protoc. 2021 Jun 20. 11(12): e4059

Differential Analysis of N-glycopeptide Abundance and N-glycosylation Site Occupancy for Studying Protein N-glycosylation Dysregulation in Human Disease.

Qi Zhang, Cheng Ma, Lian Li, Lih-Shen Chin.

  Protein N-glycosylation plays a vital role in diverse cellular processes, and dysregulated N-glycosylation is implicated in a variety of human diseases including neurodegenerative disorders and cancer. With recent advances in high-resolution mass spectrometry-based glycoproteomics technologies enabling large-scale N-glycoproteome profiling of disease and control samples, analysis of the large datasets has become a challenge. Here, we provide a protocol for the systems-level analysis of in vivo N-glycosylation sites on N-glycosylated proteins and their changes in human disease, such as Alzheimer's disease. The protocol includes quantitation and differential analysis of N-glycopeptide abundance, in addition to integrative N-glycoproteome and proteome data analyses, to determine disease-associated changes in N-glycosylation site occupancy and identify differentially N-glycosylated proteins in human disease versus control samples. This protocol can be modified and applied to study proteome-wide N-glycosylation alterations in response to different cellular stresses or pathophysiological states in other organisms or model systems.

Keywords:  Alzheimer's disease; In vivo N-glycosylation sites ; Integrative glycoproteomics and proteomics; Mass spectrometry; N-glycoproteome profiling; N-glycoproteomics; N-glycosylation site occupancy; Protein N-glycosylation

DOI:  https://doi.org/10.21769/BioProtoc.4059
Cell Rep. 2021 Jul 13. pii: S2211-1247(21)00764-6. [Epub ahead of print]36(2): 109366

A role for the ribosome-associated complex in activation of the IRE1 branch of UPR.

I-Hui Wu, Jae Seok Yoon, Qian Yang, Yi Liu, William Skach, Philip Thomas.

DOI: https://doi.org/10.1016/j.celrep.2021.109366
J Physiol. 2021 Jul 16.

Regulation of muscle and mitochondrial health by the mitochondrial fission protein Drp1 in aged mice.

Maude Dulac, Jean-Philippe Leduc-Gaudet, Marina Cefis, Marie-Belle Ayoub, Olivier Reynaud, Anwar Shams, Alaa Moamer, Marcos Francisco Nery Ferreira, Sabah Na Hussain, Gilles Gouspillou.

   KEY POINTS: The maintenance of mitochondrial integrity is critical for skeletal muscle health. Mitochondrial dynamics play key roles in mitochondrial quality control; however, the exact role that mitochondrial fission plays in the muscle aging process remains unclear. Here we report that both Drp1 knockdown and overexpression late in life in mice is detrimental to skeletal muscle function and mitochondrial health. Drp1 knockdown in 18-month-old mice resulted in severe skeletal muscle atrophy, mitochondrial dysfunction, muscle degeneration/regeneration, oxidative stress, and impaired autophagy. Overexpressing Drp1 in 18-month-old mice resulted in mild skeletal muscle atrophy and decreased mitochondrial quality. Our data indicate that silencing or overexpressing Drp1 late in life is detrimental to skeletal muscle integrity. We conclude that modulating Drp1 expression is unlikely to be a viable approach to counter the muscle aging process.
ABSTRACT: Sarcopenia, the aging-related loss of skeletal muscle mass and function, is a debilitating process negatively impacting s the quality of life of afflicted individuals. Although the mechanisms underlying sarcopenia are still only partly understood, impairments in mitochondrial dynamics, and specifically mitochondrial fission, have been proposed as an underlying mechanism. Importantly, conflicting data exist in the field and both excessive and insufficient mitochondrial fission were proposed to contribute to sarcopenia. In D. Melanogaster, enhancing mitochondrial fission in midlife through overexpression of dynamin-1-like protein (Drp1) extended lifespan and attenuated several key hallmarks of muscle aging. Whether a similar outcome of Drp1 overexpression is observed in mammalian muscles remains unknown. In this study, we investigated the impact of knocking down and overexpressing Drp1 protein for 4 months in skeletal muscles of late middle-aged (18 months) mice using intra-muscular injections of adeno-associated viruses expressing shRNA targeting Drp1 or full Drp1 cDNA. We report that knocking down Drp1 expression late in life triggers severe muscle atrophy, mitochondrial dysfunctions, degeneration/regeneration, oxidative stress and impaired autophagy. Drp1 overexpression late in life triggered mild muscle atrophy and decreased mitochondrial quality. Taken altogether, our results indicate that both overexpression or silencing Drp1 in late middle-aged mice negatively impact skeletal muscle mass and mitochondrial health. These data suggest that Drp1 content must remain within a narrow physiological range to preserve muscle and mitochondrial integrity during aging. Altering Drp1 expression is therefore unlikely to be a viable target to counter sarcopenia. This article is protected by copyright. All rights reserved.

Keywords:  autophagy; mitochondrial dynamics; mitochondrial fission; myopathic phenotype; oxidative stress; skeletal muscle aging; skeletal muscle atrophy

DOI:  https://doi.org/10.1113/JP281752
Neurosci Lett. 2021 Jul 13. pii: S0304-3940(21)00487-0. [Epub ahead of print] 136109

The Neurogenic Niche in Alzheimer's disease.

Connor M Wander, Juan Song.

  Adult hippocampal neurogenesis is the process of generation and functional incorporation of new neurons, formed by adult neural stem cells in the dentate gyrus. Adult hippocampal neurogenesis is highly dependent upon the integration of dynamic external stimuli and is instrumental in the formation of new spatial memories. Adult hippocampal neurogenesis is therefore uniquely sensitive to the summation of neuronal circuit and neuroimmune environments that comprise the neurogenic niche, and has powerful implications in diseases of aging and neurological disorders. This sensitivity underlies the neurogenic niche alterations commonly observed in Alzheimer's disease, the most common form of dementia. This review summarizes Alzheimer's disease associated changes in neuronal network activity, neuroinflammatory processes, and adult neural stem cell fate choice that ultimately result in neurogenic niche dysfunction and impaired adult hippocampal neurogenesis. A more comprehensive understanding of the complex changes mediating neurogenic niche disturbances in Alzheimer's disease will aid development of future therapies targeting adult neurogenesis.

Keywords:  Adult hippocampal neurogenesis; Alzheimer’s disease; aging; neural stem cells; neurogenic niche

DOI:  https://doi.org/10.1016/j.neulet.2021.136109
Int J Mol Cell Med. 2021 ;10(1): 1-10

Adult Hippocampal Neurogenesis and Alzheimer's Disease: Novel Application of Mesenchymal Stem Cells and their Role in Hippocampal Neurogenesis.

Mahdi Noureddini, Saeid Bagheri-Mohammadi.

  The neurogenesis can occur in two regions of the adult mammalian brain throughout the lifespan: the subgranular zone of the hippocampal dentate gyrus, and the subventricular zone of the lateral ventricle. The proliferation and maturation of neural progenitor cells are tightly regulated through intrinsic and extrinsic factors. The integration of maturated cells into the circuitry of the adult hippocampus emphasizes the importance of adult hippocampal neurogenesis in learning and memory. There is a large body of evidence demonstrating that alteration in the neurogenesis process in the adult hippocampus results in an early event in the course of Alzheimer's disease (AD). In AD condition, the number and maturation of neurons declines progressively in the hippocampus. Innovative therapies are required to modulate brain homeostasis. Mesenchymal stem cells (MSCs) hold an immense potential to regulate the neurogenesis process, and are currently tested in some brain-related disorders, such as AD. Therefore, the aim of this review is to discuss the use of MSCs to regulate endogenous adult neurogenesis and their significant impact on future strategies for the treatment of AD.

Keywords:  Alzheimer's disease; cell therapy; hippocampus; neural stem cells; neurogenesis

DOI:  https://doi.org/10.22088/IJMCM.BUMS.10.1.1
Aging (Albany NY). 2021 Jul 12. 13(undefined):

Inhibition of heat shock proteins increases autophagosome formation, and reduces the expression of APP, Tau, SOD1 G93A and TDP-43.

Paul Dent, Laurence Booth, Jane L Roberts, Andrew Poklepovic, Derek Cridebring, Eric M Reiman.

  Aberrant expression and denaturation of Tau, amyloid-beta and TDP-43 can lead to cell death and is a major component of pathologies such as Alzheimer's Disease (AD). AD neurons exhibit a reduced ability to form autophagosomes and degrade proteins via autophagy. Using genetically manipulated colon cancer cells we determined whether drugs that directly inhibit the chaperone ATPase activity or cause chaperone degradation and endoplasmic reticulum stress signaling leading to macroautophagy could reduce the levels of these proteins. The antiviral chaperone ATPase inhibitor AR12 reduced the ATPase activities and total expression of GRP78, HSP90, and HSP70, and of Tau, Tau 301L, APP, APP692, APP715, SOD1 G93A and TDP-43. In parallel, it increased the phosphorylation of ATG13 S318 and eIF2A S51 and caused eIF2A-dependent autophagosome formation and autophagic flux. Knock down of Beclin1 or ATG5 prevented chaperone, APP and Tau degradation. Neratinib, used to treat HER2+ breast cancer, reduced chaperone levels and expression of Tau and APP via macroautophagy, and neratinib interacted with AR12 to cause further reductions in protein levels. The autophagy-regulatory protein ATG16L1 is expressed as two isoforms, T300 or A300: Africans trend to express T300 and Europeans A300. We observed higher basal expression of Tau in T300 cells when compared to isogenic A300 cells. ATG16L1 isoform expression did not alter basal levels of HSP90, HSP70 or HSP27, however, basal levels of GRP78 were reduced in A300 cells. The abilities of both AR12 and neratinib to stimulate ATG13 S318 and eIF2A S51 phosphorylation and autophagic flux was also reduced in A300 cells. Our data support further evaluation of AR12 and neratinib in neuronal cells as repurposed treatments for AD.

Keywords:  Alzheimer's; GRP78; autophagy; chaperone; neratinib

DOI:  https://doi.org/10.18632/aging.203297
Ageing Res Rev. 2021 Jul 06. pii: S1568-1637(21)00151-3. [Epub ahead of print]70 101404

The protein inputs of an ultra-predictive aging clock represent viable anti-aging drug targets.

Adiv A Johnson, Maxim N Shokhirev, Benoit Lehallier.

  Machine learning models capable of predicting age given a set of inputs are referred to as aging clocks. We recently developed an aging clock that utilizes 491 plasma protein inputs, has an exceptional accuracy, and is capable of measuring biological age. Here, we demonstrate that this clock is extremely predictive (r = 0.95) when used to measure age in a novel plasma proteomic dataset derived from 370 human subjects aged 18-69 years. Over-representation analyses of the proteins that make up this clock in the Gene Ontology and Reactome databases predominantly implicated innate and adaptive immune system processes. Immunological drugs and various age-related diseases were enriched in the DrugBank and GLAD4U databases. By performing an extensive literature review, we find that at least 269 (54.8 %) of these inputs regulate lifespan and/or induce changes relevant to age-related disease when manipulated in an animal model. We also show that, in a large plasma proteomic dataset, the majority (57.2 %) of measurable clock proteins significantly change their expression level with human age. Different subsets of proteins were overlapped with distinct epigenetic, transcriptomic, and proteomic aging clocks. These findings indicate that the inputs of this age predictor likely represent a rich source of anti-aging drug targets.

Keywords:  Age prediction; Aging clock; Bioinformatics; Biomarker; Healthspan; Machine learning

DOI:  https://doi.org/10.1016/j.arr.2021.101404
Adv Exp Med Biol. 2021 ;1208 67-77

Autophagosome Trafficking.

Jingjing Ye, Ming Zheng.

Autophagy is a major intracellular degradation/recycling system that ubiquitously exists in eukaryotic cells. Autophagy contributes to the turnover of cellular components through engulfing portions of the cytoplasm or organelles and delivering them to the lysosomes/vacuole to be degraded. The trafficking of autophagosomes and their fusion with lysosomes are important steps that complete their maturation and degradation. In cells such as neuron, autophagosomes traffic long distances along the axon, while in other specialized cells such as cardiomyocytes, it is unclear how and even whether autophagosomes are transported. Therefore, it is important to learn more about the processes and mechanisms of autophagosome trafficking to lysosomes/vacuole during autophagy. The mechanisms of autophagosome trafficking are similar to those of other organelles trafficking within cells. The machinery mainly includes cytoskeletal systems such as actin and microtubules, motor proteins such as myosins and the dynein-dynactin complex, and other proteins like LC3 on the membrane of autophagosomes. Factors regulating autophagosome trafficking have not been widely studied. To date the main reagents identified for disrupting autophagosome trafficking include: 1. Microtubule polymerization reagents, which disrupt microtubules by interfering with microtubule dynamics, thus directly influence microtubule-dependent autophagosome trafficking 2. F-actin-depolymerizing drugs, which inhibit autophagosome formation, and also subsequently inhibit autophagosome trafficking 3. Motor protein regulators, which directly affect autophagosome trafficking.

DOI: https://doi.org/10.1007/978-981-16-2830-6_5
World J Stem Cells. 2021 Jun 26. 13(6): 659-669

Heat shock protein 20 promotes sirtuin 1-dependent cell proliferation in induced pluripotent stem cells.

Mujib Ullah, Nicole Pek Min Qian, Gustavo Yannarelli, Asma Akbar.

   BACKGROUND: Heat shock proteins (HSPs) are molecular chaperones that protect cells against cellular stresses or injury. However, it has been increasingly recognized that they also play crucial roles in regulating fundamental cellular processes. HSP20 has been implicated in cell proliferation, but conflicting studies have shown that it can either promote or suppress proliferation. The underlying mechanisms by which HSP20 regulates cell proliferation and pluripotency remain unexplored. While the effect of HSP20 on cell proliferation has been recognized, its role in inducing pluripotency in human-induced pluripotent stem cells (iPSCs) has not been addressed.
AIM: To evaluate the efficacy of HSP20 overexpression in human iPSCs and evaluate the ability to promote cell proliferation. The purpose of this study was to investigate whether overexpression of HSP20 in iPSCs can increase pluripotency and regeneration.
METHODS: We used iPSCs, which retain their potential for cell proliferation. HSP20 overexpression effectively enhanced cell proliferation and pluripotency. Overexpression of HSP20 in iPSCs was characterized by immunocytochemistry staining and real-time polymerase chain reaction. We also used cell culture, cell counting, western blotting, and flow cytometry analyses to validate HSP20 overexpression and its mechanism.
RESULTS: This study demonstrated that overexpression of HSP20 can increase the pluripotency in iPSCs. Furthermore, by overexpressing HSP20 in iPSCs, we showed that HSP20 upregulated proliferation markers, induced pluripotent genes, and drove cell proliferation in a sirtuin 1 (SIRT1)-dependent manner. These data have practical applications in the field of stem cell-based therapies where the mass expansion of cells is needed to generate large quantities of stem cell-derived cells for transplantation purposes.
CONCLUSION: We found that the overexpression of HSP20 enhanced the proliferation of iPSCs in a SIRT1-dependent manner. Herein, we established the distinct crosstalk between HSP20 and SIRT1 in regulating cell proliferation and pluripotency. Our study provides novel insights into the mechanisms controlling cell proliferation that can potentially be exploited to improve the expansion and pluripotency of human iPSCs for cell transplantation therapies. These results suggest that iPSCs overexpressing HSP20 exert regenerative and proliferative effects and may have the potential to improve clinical outcomes.

Keywords:  Heat shock protein 20; Heat shock proteins; Induced pluripotent stem cells; Pluripotency; Proliferation; Sirtuin-1; Stem cells

DOI:  https://doi.org/10.4252/wjsc.v13.i6.659
Exp Ther Med. 2021 Aug;22(2): 900

At elevated temperatures, heat shock protein genes show altered ratios of different RNAs and expression of new RNAs, including several novel HSPB1 mRNAs encoding HSP27 protein isoforms.

Xia Gao, Keyin Zhang, Haiyan Zhou, Lucas Zellmer, Chengfu Yuan, Hai Huang, Dezhong Joshua Liao.

  Heat shock proteins (HSP) serve as chaperones to maintain the physiological conformation and function of numerous cellular proteins when the ambient temperature is increased. To determine how accurate the general assumption that HSP gene expression is increased in febrile situations is, the RNA levels of the HSF1 (heat shock transcription factor 1) gene and certain HSP genes were determined in three cell lines cultured at 37˚C or 39˚C for three days. At 39˚C, the expression of HSF1, HSPB1, HSP90AA1 and HSP70A1L genes demonstrated complex changes in the ratios of expression levels between different RNA variants of the same gene. Several older versions of the RNAs of certain HSP genes that have been replaced by a newer version in the National Center for Biotechnology Information database were also detected, indicating that the older versions are actually RNA variants of these genes. The present study cloned four new RNA variants of the HSP27-encoding HSPB1 gene, which together encode three short HSP27 peptides. Reanalysis of the proteomics data from our previous studies also demonstrated that proteins from certain HSP genes could be detected simultaneously at multiple positions using SDS-PAGE, suggesting that these genes may engender multiple protein isoforms. These results collectively suggested that, besides increasing their expression, certain HSP and associated genes also use alternative transcription start sites to produce multiple RNA transcripts and use alternative splicing of a transcript to produce multiple mature RNAs, as important mechanisms for responding to an increased ambient temperature in vitro.

Keywords:  HSF1; HSPB1; RNA variants; alternative splicing; heat shock; heat shock proteins

DOI:  https://doi.org/10.3892/etm.2021.10332
Aging Med (Milton). 2021 Jun;4(2): 153-158

The mechanisms of vascular aging.

Shan Wang, Song Hu, Yongjun Mao.

  Vascular senescence is one of the hotspots in current research. With global average life expectancy increasing, delaying or reducing aging and age-related diseases has become a pressing issue for improving quality of life. Vascular senescence is an independent risk factor for age-related cardiovascular diseases (CVD) and results in the deterioration of CVD. Nevertheless, the underlying mechanisms of the vascular senescence have not been expressly illustrated. In this review, we attempt to summarize the recent literature in the field and discuss the major mechanisms involved in vascular senescence. We also underline key molecular aspects of aging-associated vascular dysfunction in the attempt to highlight potential innovative therapeutic targets to delay the onset of age-related diseases.

Keywords:  mechanisms; senescence; vascular aging

DOI:  https://doi.org/10.1002/agm2.12151
Front Aging Neurosci. 2021 ;13 690293

Alpha-Synuclein Post-translational Modifications: Implications for Pathogenesis of Lewy Body Disorders.

Nelson de Oliveira Manzanza, Lucia Sedlackova, Raj N Kalaria.

  Lewy Body Disorders (LBDs) lie within the spectrum of age-related neurodegenerative diseases now frequently categorized as the synucleinopathies. LBDs are considered to be among the second most common form of neurodegenerative dementias after Alzheimer's disease. They are progressive conditions with variable clinical symptoms embodied within specific cognitive and behavioral disorders. There are currently no effective treatments for LBDs. LBDs are histopathologically characterized by the presence of abnormal neuronal inclusions commonly known as Lewy Bodies (LBs) and extracellular Lewy Neurites (LNs). The inclusions predominantly comprise aggregates of alpha-synuclein (aSyn). It has been proposed that post-translational modifications (PTMs) such as aSyn phosphorylation, ubiquitination SUMOylation, Nitration, o-GlcNacylation, and Truncation play important roles in the formation of toxic forms of the protein, which consequently facilitates the formation of these inclusions. This review focuses on the role of different PTMs in aSyn in the pathogenesis of LBDs. We highlight how these PTMs interact with aSyn to promote misfolding and aggregation and interplay with cell membranes leading to the potential functional and pathogenic consequences detected so far, and their involvement in the development of LBDs.

Keywords:  Lewy body disorders; alpha synuclein; dementia; neuronal membrane; post-translational modifications

DOI:  https://doi.org/10.3389/fnagi.2021.690293
Acta Pharmacol Sin. 2021 Jul 09.

Age-dependent alterations in key components of the nigrostriatal dopaminergic system and distinct motor phenotypes.

Jiang-Peng Fan, Hui-Zhen Geng, Ya-Wei Ji, Tao Jia, Jennifer B Treweek, An-An Li, Chun-Yi Zhou, Viviana Gradinaru, Cheng Xiao.

  The nigrostriatal dopaminergic (DA) system, which includes DA neurons in the ventral and dorsal tiers of the substantia nigra pars compacta (vSNc, dSNc) and DA terminals in the dorsal striatum, is critically implicated in motor control. Accumulating studies demonstrate that both the nigrostriatal DA system and motor function are impaired in aged subjects. However, it is unknown whether dSNc and vSNc DA neurons and striatal DA terminals age in similar patterns, and whether these changes parallel motor deficits. To address this, we performed ex vivo patch-clamp recordings in dSNc and vSNc DA neurons, measured striatal dopamine release, and analyzed motor behaviors in rodents. Spontaneous firing in dSNc and vSNc DA neurons and depolarization-evoked firing in dSNc DA neurons showed inverse V-shaped changes with age. But depolarization-evoked firing in vSNc DA neurons increased with age. In the dorsal striatum, dopamine release declined with age. In locomotor tests, 12-month-old rodents showed hyperactive exploration, relative to 6- and 24-month-old rodents. Additionally, aged rodents showed significant deficits in coordination. Elevating dopamine levels with a dopamine transporter inhibitor improved both locomotion and coordination. Therefore, key components in the nigrostriatal DA system exhibit distinct aging patterns and may contribute to age-related alterations in locomotion and coordination.

Keywords:  aging; coordination; dopamine sensor; dopaminergic neurons; locomotion; rodent; substantia nigra pars compacta

DOI:  https://doi.org/10.1038/s41401-021-00713-5
Cell Signal. 2021 Jul 07. pii: S0898-6568(21)00165-0. [Epub ahead of print]86 110076

Protein disulfide isomerase inhibits endoplasmic reticulum stress response and apoptosis via its oxidoreductase activity in colorectal cancer.

Yu-Shui Ma, Sun Feng, Lan Lin, Hui Zhang, Guo-Hua Wei, Yu-Shan Liu, Xiao-Li Yang, Rui Xin, Yi Shi, Dan-Dan Zhang, Cheng-You Jia, Gai-Xia Lu, Shao-Bo Xue, Fei Yu, Zhong-Wei Lv, Ji-Bin Liu, Gao-Ren Wang, Da Fu.

  Protein disulfide isomerase (PDI), a principal endoplasmic reticulum resident oxidoreductase chaperone, is known to play a role in malignancies. This study aims to explore the molecular mechanism by which PDI regulates endoplasmic reticulum stress and the apoptosis signaling pathway in colorectal cancer (CRC). We determined the expression of PDI in CRC tissues and adjacent normal tissues. Gain- and loss- of function assays were conducted to evaluate the effects of PDI on oxidative stress, endoplasmic reticulum stress, and apoptosis in CRC cells, as reflected by hydrogen peroxide (H2O2) level and the expression of related proteins. PDI protein expression was upregulated in CRC tissues. Small molecule inhibitor of PDI or PDI knockdown reduced CRC cell viability and induced apoptosis. Overexpression of wild-type PDI augmented the viability of CRC cells and inhibited endoplasmic reticulum stress response and apoptosis. Small molecule inhibitor of PDI or PDI knockdown increased intracellular H2O2 level and activated apoptosis signaling pathway, which could be reversed by wild-type PDI restoration. Moreover, the catalytic active site of C-terminal of PDI was found to be indispensable for the regulatory effects of PDI on H2O2 levels, apoptosis and cell viability in CRC cells. Collectively, PDI inhibits endoplasmic reticulum stress and apoptosis of CRC cells through its oxidoreductase activity, thereby promoting the malignancy of CRC.

Keywords:  Apoptosis; Cell viability; Colorectal cancer protein disulfide isomerase; Endoplasmic reticulum stress; Hydrogen peroxide; Oxidative stress response

DOI:  https://doi.org/10.1016/j.cellsig.2021.110076
Acta Pharmacol Sin. 2021 Jul 15.

Luteolin alleviates cognitive impairment in Alzheimer's disease mouse model via inhibiting endoplasmic reticulum stress-dependent neuroinflammation.

Jie-Jian Kou, Jun-Zhuo Shi, Yang-Yang He, Jiao-Jiao Hao, Hai-Yu Zhang, Dong-Mei Luo, Jun-Ke Song, Yi Yan, Xin-Mei Xie, Guan-Hua Du, Xiao-Bin Pang.

  Luteolin is a flavonoid in a variety of fruits, vegetables, and herbs, which has shown anti-inflammatory, antioxidant, and anti-cancer neuroprotective activities. In this study, we investigated the potential beneficial effects of luteolin on memory deficits and neuroinflammation in a triple-transgenic mouse model of Alzheimer's disease (AD) (3 × Tg-AD). The mice were treated with luteolin (20, 40 mg · kg-1 · d-1, ip) for 3 weeks. We showed that luteolin treatment dose-dependently improved spatial learning, ameliorated memory deficits in 3 × Tg-AD mice, accompanied by inhibiting astrocyte overactivation (GFAP) and neuroinflammation (TNF-α, IL-1β, IL-6, NO, COX-2, and iNOS protein), and decreasing the expression of endoplasmic reticulum (ER) stress markers GRP78 and IRE1α in brain tissues. In rat C6 glioma cells, treatment with luteolin (1, 10 µM) dose-dependently inhibited LPS-induced cell proliferation, excessive release of inflammatory cytokines, and increase of ER stress marker GRP78. In conclusion, luteolin is an effective agent in the treatment of learning and memory deficits in 3 × Tg-AD mice, which may be attributable to the inhibition of ER stress in astrocytes and subsequent neuroinflammation. These results provide the experimental basis for further research and development of luteolin as a therapeutic agent for AD.

Keywords:  3 × Tg-AD mice; Alzheimer’s disease; C6 cells; astrocyte; endoplasmic reticulum stress; luteolin; neuroinflammation

DOI:  https://doi.org/10.1038/s41401-021-00702-8
Curr Stem Cell Res Ther. 2021 Jul 11.

Hippo signaling: A stress response pathway in stem cells.

Naciye Dilara Zeybek, Eylem Baysal, Ozlem Bozdemir, Esra Buber.

  The Hippo pathway, with its core components and the downstream transcriptional coactivators, controls the self-renewable capacity and stemness features of stem cells and serves as a stress response pathway by regulating proliferation, differentiation, and apoptosis. The Hippo pathway interaction with other signaling ways plays a vital role in response to various stress stimuli arising from energy metabolism, hypoxia, reactive oxygen species, and mechanical forces. Depending on the energy levels, the Hippo pathway is regulated by AMP-activated protein kinase (AMPK) and mechanistic target of rapamycin (mTOR), which in turn determines stem cell proliferation (cell survival and growth) and differentiation. Oxidative stress-driven by ROS production also affects the Hippo pathway with transcriptional changes through MST/YAP/FoxO pathway and leads to the activation of pro-apoptotic genes and eventually cell death. HIF1alpha/YAP signaling is critical for the long-term maintenance of mesenchymal stem cells (MSCs) under hypoxia. In this review, we present an overview of stem cell response to stress, including mechanical, hypoxia, metabolic and oxidative stress through the modulation of the Hippo pathway. The biological effects such as autophagy, apoptosis and senescence were discussed in the context of the Hippo pathway in stem cells.

Keywords:  Hippo pathway; YAP/TAZ; autophagy; hypoxia; oxidative stress; stem cell; stress

DOI:  https://doi.org/10.2174/1574888X16666210712100002
Front Genet. 2021 ;12 600632

Analysis of Age-Related Circular RNA Expression Profiles in Mesenchymal Stem Cells of Rat Bone Marrow.

Hui Sun, Yanan Sun, Xiao Yu, Xingyu Gao, Huan Wang, Lin Zhang, Yingai Shi, Xu He.

  As multicellular organisms age, they undergo a reduction in tissue and organ function. Researchers have put forward a theory that stem cell aging is the main factor responsible for decreased tissue and organ function. The adult stem cells guarantee the maintenance and repair of adult tissues and organs. Among adult stem cells, mesenchymal stem cells (MSCs) are emerging as hopeful candidates for cell-based therapy of numerous diseases. In recent years, high-throughput sequencing technologies have evolved to identify circular RNAs (circRNAs) associated with an increasing number of diseases, such as cancer and age-related diseases. It has been reported that circRNAs can compete with microRNAs (miRNAs) to affect the stability or translation of target RNAs and further regulate gene expression at the transcriptional level. However, the role of circRNAs expressed in MSCs in aging mechanisms has not yet been deciphered. The aim of this study was to explore and analyze the expression profiles of age-related circRNAs in MSCs. In this study, bone marrow MSCs were extracted from aged and young rats and analyzed using high-throughput sequencing and bioinformatics. The reliability of high-throughput RNA sequencing was verified by quantitative real-time polymerase chain reaction. The most important circRNA functions and pathways were further selected by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomics (KEGG) analysis. Age-related circRNAs were found in the circrNA-miRNA-mRNA interaction network. The results of high-throughput sequencing showed that 4,229 circRNAs were involved in age-related senescence of MSCs. Compared with the young group, there were 29 differentially expressed circRNAs in the aged group, of which four were upregulated and 25 were downregulated. GO analysis covered three domains: biological process (BP), cellular component (CC), and molecular function (MF). The terms assigned to the BP domain were cellular metabolic processes and cellular macromolecule metabolic processes. The identified CC terms were intracellular and intracellular part, and the identified MF terms were binding and protein binding. The top five KEGG pathways were mitophagy-animal-Rattus norvegicus, prostate cancer-Rattus norvegicus, pathways in cancer-Rattus norvegicus, lysosome-Rattus norvegicus, and autophagy-animal-Rattus norvegicus. Altogether, circRNAs may play a major role in age-related MSC senescence. This study provides new mechanistic insights into MSC senescence, possibly leading to novel therapeutic strategies for age-related diseases.

Keywords:  MSCs; bioinformatics; circular RNA; high-throughput sequencing; senescence

DOI:  https://doi.org/10.3389/fgene.2021.600632
Nat Rev Mol Cell Biol. 2021 Jul 16.

Translational control of stem cell function.

James A Saba, Kifayathullah Liakath-Ali, Rachel Green, Fiona M Watt.

Stem cells are characterized by their ability to self-renew and differentiate into many different cell types. Research has focused primarily on how these processes are regulated at a transcriptional level. However, recent studies have indicated that stem cell behaviour is strongly coupled to the regulation of protein synthesis by the ribosome. In this Review, we discuss how different translation mechanisms control the function of adult and embryonic stem cells. Stem cells are characterized by low global translation rates despite high levels of ribosome biogenesis. The maintenance of pluripotency, the commitment to a specific cell fate and the switch to cell differentiation depend on the tight regulation of protein synthesis and ribosome biogenesis. Translation regulatory mechanisms that impact on stem cell function include mTOR signalling, ribosome levels, and mRNA and tRNA features and amounts. Understanding these mechanisms important for stem cell self-renewal and differentiation may also guide our understanding of cancer grade and metastasis.

DOI: https://doi.org/10.1038/s41580-021-00386-2
Adv Exp Med Biol. 2021 ;1208 289-309

Chemical Autophagy Regulators.

Ya-Ping Yang, Fen Wang, Chun-Feng Liu.

Autophagy is a catabolic process that removes aggregated proteins and damaged organelles via lysosomal degradation. Increasing evidence suggests that dysfunction of autophagy is associated with a variety of human pathologies, including aging, cancer, neurodegenerative diseases, heart diseases, diabetes, and other metabolic diseases. Current research suggests that the regulation of autophagy may be a novel target for the treatment of these diseases. For this purpose, it is essential to have a deep understanding on the molecular details of autophagy and its regulatory network in each of the disease contexts. Over the years, a variety of chemical autophagy inducers and inhibitors has been developed. The application of these autophagy regulators can assist us in the exploration of the mechanism and therapeutic potential of autophagy regulation. In this chapter, we summarize the recent advances in chemical autophagy regulators to provide methodological support for autophagy research.

DOI: https://doi.org/10.1007/978-981-16-2830-6_13
Mol Neurodegener. 2021 Jul 15. 16(1): 47

Knock-in models related to Alzheimer's disease: synaptic transmission, plaques and the role of microglia.

Diana P Benitez, Shenyi Jiang, Jack Wood, Rui Wang, Chloe M Hall, Carlijn Peerboom, Natalie Wong, Katie M Stringer, Karina S Vitanova, Victoria C Smith, Dhaval Joshi, Takashi Saito, Takaomi C Saido, John Hardy, Jörg Hanrieder, Bart De Strooper, Dervis A Salih, Takshashila Tripathi, Frances A Edwards, Damian M Cummings.

   BACKGROUND: Microglia are active modulators of Alzheimer's disease but their role in relation to amyloid plaques and synaptic changes due to rising amyloid beta is unclear. We add novel findings concerning these relationships and investigate which of our previously reported results from transgenic mice can be validated in knock-in mice, in which overexpression and other artefacts of transgenic technology are avoided.
METHODS: AppNL-F and AppNL-G-F knock-in mice expressing humanised amyloid beta with mutations in App that cause familial Alzheimer's disease were compared to wild type mice throughout life. In vitro approaches were used to understand microglial alterations at the genetic and protein levels and synaptic function and plasticity in CA1 hippocampal neurones, each in relationship to both age and stage of amyloid beta pathology. The contribution of microglia to neuronal function was further investigated by ablating microglia with CSF1R inhibitor PLX5622.
RESULTS: Both App knock-in lines showed increased glutamate release probability prior to detection of plaques. Consistent with results in transgenic mice, this persisted throughout life in AppNL-F mice but was not evident in AppNL-G-F with sparse plaques. Unlike transgenic mice, loss of spontaneous excitatory activity only occurred at the latest stages, while no change could be detected in spontaneous inhibitory synaptic transmission or magnitude of long-term potentiation. Also, in contrast to transgenic mice, the microglial response in both App knock-in lines was delayed until a moderate plaque load developed. Surviving PLX5266-depleted microglia tended to be CD68-positive. Partial microglial ablation led to aged but not young wild type animals mimicking the increased glutamate release probability in App knock-ins and exacerbated the App knock-in phenotype. Complete ablation was less effective in altering synaptic function, while neither treatment altered plaque load.
CONCLUSIONS: Increased glutamate release probability is similar across knock-in and transgenic mouse models of Alzheimer's disease, likely reflecting acute physiological effects of soluble amyloid beta. Microglia respond later to increased amyloid beta levels by proliferating and upregulating Cd68 and Trem2. Partial depletion of microglia suggests that, in wild type mice, alteration of surviving phagocytic microglia, rather than microglial loss, drives age-dependent effects on glutamate release that become exacerbated in Alzheimer's disease.

Keywords:  Ageing; Alzheimer’s disease; Amyloid beta; Gene expression; Microglia; Neurodegeneration; Plaques; Synaptic plasticity; Synaptic transmission; TREM2

DOI:  https://doi.org/10.1186/s13024-021-00457-0
Mol Cell. 2021 Jul 05. pii: S1097-2765(21)00497-4. [Epub ahead of print]

An mTORC1-GRASP55 signaling axis controls unconventional secretion to reshape the extracellular proteome upon stress.

Julian Nüchel, Marina Tauber, Janica L Nolte, Matthias Mörgelin, Clara Türk, Beate Eckes, Constantinos Demetriades, Markus Plomann.

  Cells communicate with their environment via surface proteins and secreted factors. Unconventional protein secretion (UPS) is an evolutionarily conserved process, via which distinct cargo proteins are secreted upon stress. Most UPS types depend upon the Golgi-associated GRASP55 protein. However, its regulation and biological role remain poorly understood. Here, we show that the mechanistic target of rapamycin complex 1 (mTORC1) directly phosphorylates GRASP55 to maintain its Golgi localization, thus revealing a physiological role for mTORC1 at this organelle. Stimuli that inhibit mTORC1 cause GRASP55 dephosphorylation and relocalization to UPS compartments. Through multiple, unbiased, proteomic analyses, we identify numerous cargoes that follow this unconventional secretory route to reshape the cellular secretome and surfactome. Using MMP2 secretion as a proxy for UPS, we provide important insights on its regulation and physiological role. Collectively, our findings reveal the mTORC1-GRASP55 signaling hub as the integration point in stress signaling upstream of UPS and as a key coordinator of the cellular adaptation to stress.

Keywords:  ECM; GORASP2; GRASP55; Golgi; MMP2; Rapamycin; Tuberous Sclerosis Complex (TSC); cellular stress response; mTORC1; unconventional protein secretion (UPS)

DOI:  https://doi.org/10.1016/j.molcel.2021.06.017
EMBO J. 2021 Jul 13. e105603

PIP2 depletion and altered endocytosis caused by expression of Alzheimer's disease-protective variant PLCγ2 R522.

Emily Maguire, Georgina E Menzies, Thomas Phillips, Michael Sasner, Harriet M Williams, Magdalena A Czubala, Neil Evans, Emma L Cope, Rebecca Sims, Gareth R Howell, Emyr Lloyd-Evans, Julie Williams, Nicholas D Allen, Philip R Taylor.

  Variants identified in genome-wide association studies have implicated immune pathways in the development of Alzheimer's disease (AD). Here, we investigated the mechanistic basis for protection from AD associated with PLCγ2 R522, a rare coding variant of the PLCG2 gene. We studied the variant's role in macrophages and microglia of newly generated PLCG2-R522-expressing human induced pluripotent cell lines (hiPSC) and knockin mice, which exhibit normal endogenous PLCG2 expression. In all models, cells expressing the R522 mutation show a consistent non-redundant hyperfunctionality in the context of normal expression of other PLC isoforms. This manifests as enhanced release of cellular calcium ion stores in response to physiologically relevant stimuli like Fc-receptor ligation or exposure to Aβ oligomers. Expression of the PLCγ2-R522 variant resulted in increased stimulus-dependent PIP2 depletion and reduced basal PIP2 levels in vivo. Furthermore, it was associated with impaired phagocytosis and enhanced endocytosis. PLCγ2 acts downstream of other AD-related factors, such as TREM2 and CSF1R, and alterations in its activity directly impact cell function. The inherent druggability of enzymes such as PLCγ2 raises the prospect of PLCγ2 manipulation as a future therapeutic approach in AD.

Keywords:  Alzheimer’s disease; PIP2; PLCG2; microglia; phagocytosis

DOI:  https://doi.org/10.15252/embj.2020105603
Bioorg Med Chem Lett. 2021 Jul 08. pii: S0960-894X(21)00470-4. [Epub ahead of print] 128243

Improved correction of F508del-CFTR biogenesis with a folding facilitator and an inhibitor of protein ubiquitination.

Jennifer L Goeckeler-Fried, Rajiah Aldrin Denny, Disha Joshi, Clare Hill, Mads B Larsen, Annette N Chiang, Raymond A Frizzell, Peter Wipf, Eric J Sorscher, Jeffrey L Brodsky.

A growing number of diseases are linked to the misfolding of integral membrane proteins, and many of these proteins are targeted for ubiquitin-proteasome-dependent degradation. One such substrate is a mutant form of the Cystic Fibrosis Transmembrane Conductance Regulator (F508del-CFTR). Protein folding "correctors" that repair the F508del-CFTR folding defect have entered the clinic, but they are unlikely to protect the entire protein from degradation. To increase the pool of F508del-CFTR protein that is available for correction by existing treatments, we determined a structure-activity relationship to improve the efficacy and reduce the toxicity of an inhibitor of the E1 ubiquitin activating enzyme that facilitates F508del-CFTR maturation. A resulting lead compound lacked measurable toxicity and improved the ability of an FDA-approved corrector to augment F508del-CFTR folding, transport the protein to the plasma membrane, and maintain its activity. These data support a proof-of-concept that modest inhibition of substrate ubiquitination improves the activity of small molecule correctors to treat CF and potentially other protein conformational disorders.

DOI: https://doi.org/10.1016/j.bmcl.2021.128243
Dev Biol. 2021 Jul 12. pii: S0012-1606(21)00171-8. [Epub ahead of print]

The role of Ire1 in Drosophila eye pigmentation revealed by an RNase dead allele.

Sahana Mitra, Hyung Don Ryoo.

  Ire1 is an endoplasmic reticulum (ER) transmembrane RNase that cleaves substrate mRNAs to help cells adapt to ER stress. Because there are cell types with physiological ER stress, loss of Ire1 results in metabolic and developmental defects in diverse organisms. In Drosophila, Ire1 mutants show developmental defects at early larval stages and in pupal eye photoreceptor differentiation. These Drosophila studies relied on a single Ire1 loss of function allele with a Piggybac insertion in the coding sequence. Here, we report that an Ire1 allele with a specific impairment in the RNase domain, H890A, unmasks previously unrecognized Ire1 phenotypes in Drosophila eye pigmentation. Specifically, we found that the adult eye pigmentation is altered, and the pigment granules are compromised in Ire1H890A homozygous mosaic eyes. Furthermore, the Ire1H890A mutant eyes had dramatically reduced Rhodopsin-1 protein levels. Drosophila eye pigment granules are most notably associated with late endosome/lysosomal defects. Our results indicate that the loss of Ire1, which would impair ER homeostasis, also results in altered adult eye pigmentation.

Keywords:  , Pigment granules; Drosophila; Ire1; RNase; Rhodopsin-1

DOI:  https://doi.org/10.1016/j.ydbio.2021.07.008
Nature. 2021 Jul 14.

A protective signal between the brain's supporting cells in Alzheimer's disease.

Jerika J Barron, Anna V Molofsky.



Keywords:  Alzheimer's disease; Brain; Immunology; Neurodegeneration

DOI:  https://doi.org/10.1038/d41586-021-01870-7
Arch Insect Biochem Physiol. 2021 Jul 11. e21832

Role of autophagy in midgut stem cells of silkworm Bombyx mori, during larval-pupal metamorphosis.

Busra Gunay, Ebru Goncu.

  Autophagy is a critical mechanism for the self-renewal, proliferation, and differentiation of stem cells. Bombyx mori midgut has stem cells that play a role in the regeneration of the larval epithelium in larval stages and the formation of the pupal midgut epithelium during larval-pupal metamorphosis. In this study, the role of the autophagy mechanism in midgut stem cells during the formation of the pupal midgut was investigated. For this purpose, two different doses of autophagy inhibitor chloroquine were administered to B. mori larvae on days 7 and 8 of the fifth larval stage. Morphological changes during the formation process of the pupal epithelium, expression levels of autophagy-related genes Atg8 and Atg12 in stem cells, and the amounts of lysosomal enzyme acid phosphatase were determined after the application. The obtained findings were evaluated in comparison with the control groups. Abnormalities in the formation of the pupal midgut after inhibition of autophagy showed the significance of the autophagy mechanism during this period.

Keywords:  Bombyx mori; autophagy; midgut; stem cell

DOI:  https://doi.org/10.1002/arch.21832
Sci Rep. 2021 Jul 13. 11(1): 14391

Exogenous misfolded protein oligomers can cross the intestinal barrier and cause a disease phenotype in C. elegans.

Michele Perni, Benedetta Mannini, Catherine K Xu, Janet R Kumita, Christopher M Dobson, Fabrizio Chiti, Michele Vendruscolo.

Misfolded protein oligomers are increasingly recognized as highly cytotoxic agents in a wide range of human disorders associated with protein aggregation. In this study, we assessed the possible uptake and resulting toxic effects of model protein oligomers administered to C. elegans through the culture medium. We used an automated machine-vision, high-throughput screening procedure to monitor the phenotypic changes in the worms, in combination with confocal microscopy to monitor the diffusion of the oligomers, and oxidative stress assays to detect their toxic effects. Our results suggest that the oligomers can diffuse from the intestinal lumen to other tissues, resulting in a disease phenotype. We also observed that pre-incubation of the oligomers with a molecular chaperone (αB-crystallin) or a small molecule inhibitor of protein aggregation (squalamine), reduced the oligomer absorption. These results indicate that exogenous misfolded protein oligomers can be taken up by the worms from their environment and spread across tissues, giving rise to pathological effects in regions distant from their place of absorbance.

DOI: https://doi.org/10.1038/s41598-021-93527-8
Brain. 2021 Jul 15. pii: awab268. [Epub ahead of print]

The role of mTORC1 activation in seizure-induced exacerbation of Alzheimer's disease.

Sarah Gourmaud, David A Stewart, David J Irwin, Nicholas Roberts, Aaron J Barbour, Grace Eberwine, William T O'Brien, Robert Vassar, Delia M Talos, Frances E Jensen.

  Seizure risk is 10-fold higher in Alzheimer's disease patients than the general population, yet the mechanisms underlying this susceptibility and the effects of seizures on Alzheimer's disease are poorly understood. To elucidate our proposed bidirectional relationship between Alzheimer's disease and seizures, we studied Alzheimer's disease human brain samples (n = 34) and found that patients with a history of seizures (n = 14) had increased β-amyloid and tau pathology, and upregulation of the mechanistic target of rapamycin (mTOR) pathway compared to cases without known seizure history (n = 20). To establish whether seizures could accelerate Alzheimer's disease progression, we induced chronic hyperexcitability in the 5XFAD Alzheimer's disease mouse model by kindling with the chemoconvulsant pentylenetetrazol and observed that 5XFAD mice displayed higher seizure severity compared to wild type. Furthermore, kindled seizures exacerbated later cognitive impairment, Alzheimer's disease neuropathology and mTORC1 activation. Finally, we demonstrate that administration of the mTOR inhibitor rapamycin following kindled seizures rescued enhanced remote and long-term memory deficits associated with earlier kindling and prevented the seizure-induced increases in Alzheimer's disease neuropathology. These data demonstrate an important link between chronic hyperexcitability and progressive Alzheimer's disease pathology and suggest a mechanism whereby rapamycin may serve as an adjunct therapy to attenuate Alzheimer's disease progression.

Keywords:  Alzheimer’s disease; cognition; mTOR; neuropathology; seizures

DOI:  https://doi.org/10.1093/brain/awab268
Cell Mol Life Sci. 2021 Jul 10.

Distinct states of proinsulin misfolding in MIDY.

Leena Haataja, Anoop Arunagiri, Anis Hassan, Kaitlin Regan, Billy Tsai, Balamurugan Dhayalan, Michael A Weiss, Ming Liu, Peter Arvan.

  A precondition for efficient proinsulin export from the endoplasmic reticulum (ER) is that proinsulin meets ER quality control folding requirements, including formation of the Cys(B19)-Cys(A20) "interchain" disulfide bond, facilitating formation of the Cys(B7)-Cys(A7) bridge. The third proinsulin disulfide, Cys(A6)-Cys(A11), is not required for anterograde trafficking, i.e., a "lose-A6/A11" mutant [Cys(A6), Cys(A11) both converted to Ser] is well secreted. Nevertheless, an unpaired Cys(A11) can participate in disulfide mispairings, causing ER retention of proinsulin. Among the many missense mutations causing the syndrome of Mutant INS gene-induced Diabetes of Youth (MIDY), all seem to exhibit perturbed proinsulin disulfide bond formation. Here, we have examined a series of seven MIDY mutants [including G(B8)V, Y(B26)C, L(A16)P, H(B5)D, V(B18)A, R(Cpep + 2)C, E(A4)K], six of which are essentially completely blocked in export from the ER in pancreatic β-cells. Three of these mutants, however, must disrupt the Cys(A6)-Cys(A11) pairing to expose a critical unpaired cysteine thiol perturbation of proinsulin folding and ER export, because when introduced into the proinsulin lose-A6/A11 background, these mutants exhibit native-like disulfide bonding and improved trafficking. This maneuver also ameliorates dominant-negative blockade of export of co-expressed wild-type proinsulin. A growing molecular understanding of proinsulin misfolding may permit allele-specific pharmacological targeting for some MIDY mutants.

Keywords:  Diabetes; Disulfide bonds; Endoplasmic reticulum; Insulin; Protein trafficking

DOI:  https://doi.org/10.1007/s00018-021-03871-1
Cell Rep. 2021 Jul 13. pii: S2211-1247(21)00759-2. [Epub ahead of print]36(2): 109361

Site-specific O-GlcNAcylation of Psme3 maintains mouse stem cell pluripotency by impairing P-body homeostasis.

Federico Pecori, Nanako Kondo, Chika Ogura, Taichi Miura, Masahiko Kume, Youhei Minamijima, Kazuo Yamamoto, Shoko Nishihara.

  Mouse embryonic stem cell (ESC) pluripotency is tightly regulated by a complex network composed of extrinsic and intrinsic factors that allow proper organismal development. O-linked β-N-acetylglucosamine (O-GlcNAc) is the sole glycosylation mark found on cytoplasmic and nuclear proteins and plays a pivotal role in regulating fundamental cellular processes; however, its function in ESC pluripotency is still largely unexplored. Here, we identify O-GlcNAcylation of proteasome activator subunit 3 (Psme3) protein as a node of the ESC pluripotency network. Mechanistically, O-GlcNAc modification of serine 111 (S111) of Psme3 promotes degradation of Ddx6, which is essential for processing body (P-body) assembly, resulting in the maintenance of ESC pluripotent state. Conversely, loss of Psme3 S111 O-GlcNAcylation stabilizes Ddx6 and increases P-body levels, culminating in spontaneous exit of ESC from the pluripotent state. Our findings establish O-GlcNAcylation at S111 of Psme3 as a switch that regulates ESC pluripotency via control of P-body homeostasis.

Keywords:  Ddx6; O-GlcNAc; P-bodies; PA28γ; Psme3; embryonic stem cells; glycosylation; phase separation; pluripotency; proteasome

DOI:  https://doi.org/10.1016/j.celrep.2021.109361
Phytomedicine. 2021 May 21. pii: S0944-7113(21)00141-0. [Epub ahead of print]89 153599

Citrus alkaline extracts prevent endoplasmic reticulum stress in type II alveolar epithelial cells to ameliorate pulmonary fibrosis via the ATF3/PINK1 pathway.

Zhichao Wang, Fanchao Feng, Hailang He, Qi Wu, Cheng Gu, Jonathan Hrovat, Wenpan Peng, Yong Xu, Di Han, Ping Yang, Xianmei Zhou, Jianxin Li, Jinjun Shan.

   BACKGROUND: Idiopathic pulmonary fibrosis is a chronic, progressive, fibrotic disease. Although the pathogenesis remains unclear, the effect of endoplasmic reticulum (ER) stress in type II alveolar epithelial cells (AEC IIs) is increasingly thought to be a critical mechanism.
PURPOSE: We investigated the effects of citrus alkaline extracts (CAE) on AEC IIs and elucidated the underlying mechanism for their possible use in ameliorating pulmonary fibrosis (PF).
METHODS: A bleomycin-induced mouse model of PF, and an in vitro tunicamycin (TM) -induced ER stress model in A549 cells were successfully established. Accumulation of collagen in lung tissues in vivo was assessed using histological analysis and western blotting. The expression levels of the ER-stress marker BiP and other related proteins were assessed by western blotting and immunofluorescence staining. Mitochondrial membrane potential was assessed to evaluate mitochondrial homeostasis.
RESULTS: CAE mitigated collagen deposition to ameliorate PF in vivo. CAE suppressed the bleomycin or TM-induced increases in ER-stress biomarker, BiP, and PERK pathway proteins, resulting in a decrease in ER stress in mouse lung tissues and A549 cells, respectively. Additionally, CAE treatment suppressed the bleomycin or TM-induced increase in the ER-stress downstream proteins, activating ATF3 and increased the levels of PINK1 in AEC IIs, both in vivo and in vitro. The reduced mitochondrial homeostasis induced by TM was restored by CAE-treatment in A549 cells. Furthermore, conditioned media from TM-treated A549 cells increased collagen deposition in MRC5 cells mainly via TGF-β1. The increased collagen deposition was not seen using conditioned media from CAE-treated A549 cells.
CONCLUSION: These results provide novel insights into the potential mechanism of CAE in inhibiting ER stress in AEC IIs, and suggests that it has great potential to ameliorate PF via the ATF3/PINK1 pathway.

Keywords:  ATF3; Citrus alkaline extracts; Endoplasmic reticulum stress; PINK1; Pulmonary fibrosis

DOI:  https://doi.org/10.1016/j.phymed.2021.153599
Handb Clin Neurol. 2021 ;pii: B978-0-12-819973-2.00030-7. [Epub ahead of print]182 317-329

Olfaction as an early marker of Parkinson's disease and Alzheimer's disease.

Ian M Walker, Michelle E Fullard, James F Morley, John E Duda.

  Olfactory impairment is a common and early sign of Parkinson's disease (PD) and Alzheimer's disease (AD), the two most prevalent neurodegenerative conditions in the elderly. This phenomenon corresponds to pathologic processes emerging in the olfactory system prior to the onset of typical clinical manifestations. Clinically available tests can establish hyposmia through odor identification assessment, discrimination, and odor detection threshold. There are significant efforts to develop preventative or disease-modifying therapies that slow down or halt the progression of PD and AD. Due to the convenience and low cost of its assessment, olfactory impairment could be used in these studies as a screening instrument. In the clinical setting, loss of smell may also help to differentiate PD and AD from alternative causes of Parkinsonism and cognitive impairment, respectively. Here, we discuss the pathophysiology of olfactory dysfunction in PD and AD and how it can be assessed in the clinical setting to aid in the early and differential diagnosis of these disorders.

Keywords:  Alzheimer's disease; Biomarker; Cognitive impairment; Dementia; Olfaction; Parkinson's disease; Parkinsonism

DOI:  https://doi.org/10.1016/B978-0-12-819973-2.00030-7
J Biol Chem. 2021 Jul 13. pii: S0021-9258(21)00678-5. [Epub ahead of print] 100878

A new model for sensitive detection of zoonotic prions by PrP transgenic Drosophila.

Alana M Thackray, Olivier Andréoletti, John Spiropoulos, Raymond Bujdoso.

  Prions are transmissible protein pathogens most reliably detected by bioassay in a suitable host, typically mice. However, the mouse bioassay is slow and cumbersome, and relatively insensitive to low titres of prion infectivity. Prions can be detected biochemically in vitro by the protein misfolding cyclic amplification (PMCA) technique, which amplifies disease-associated prion protein but does not detect bona fide prion infectivity. Here we demonstrate that Drosophila transgenic for bovine PrP expression can serve as a model system for the detection of bovine prions significantly more efficiently than either the mouse prion bioassay or PMCA. Strikingly, bovine PrP transgenic Drosophila could detect bovine prion infectivity in the region of a 10-12 dilution of classical bovine spongiform encephalopathy (BSE) inoculum, which is 106-fold more sensitive than that achieved by the bovine PrP mouse bioassay. A similar level of sensitivity was observed in the detection of H-type and L-type atypical BSE and sheep-passaged BSE by bovine PrP transgenic Drosophila. Bioassays of bovine prions in Drosophila were performed within 7 weeks, whereas the mouse prion bioassay required at least a year to assess the same inoculum. In addition, bovine PrP transgenic Drosophila could detect classical BSE at a level 105-fold lower than that achieved by PMCA. These data show that PrP transgenic Drosophila represent a new tractable prion bioassay for the efficient and sensitive detection of mammalian prions, including those of known zoonotic potential.

Keywords:  Bioassay; Drosophila; PrP(Sc); classical and atypical BSE; infectious disease; mouse; neurodegenerative disease; prion; protein misfolding

DOI:  https://doi.org/10.1016/j.jbc.2021.100878