bims-proarb 2022-10-23 papers

bims-proarb

Biomed News

on Proteostasis in aging and regenerative biology

Issue of 2022‒10‒23
nineteen papers selected by
Rich Giadone
Harvard University

Heat Shock Protein Hspa13 Regulates Endoplasmic Reticulum and Cytosolic Proteostasis Through Modulation of Protein Translocation.
The unfolded protein response reverses the effects of glucose on lifespan in chemically-sterilized C. elegans.
Nucleosome proteostasis and histone turnover.
Functions of autophagy in chloroplast protein degradation and homeostasis.
Single cell transcriptomic profiling of a neuron-astrocyte assembloid tauopathy model.
Disruption of proteostasis causes IRE1 mediated reprogramming of alveolar epithelial cells.
Translational reprogramming in response to accumulating stressors ensures critical threshold levels of Hsp90 for mammalian life.
Endothelial cell autophagy in the context of disease development.
Autophagy Regulates Osteogenic Differentiation of Human Periodontal Ligament Stem Cells Induced by Orthodontic Tension.
A consolidated review on stem cell therapy for treatment and management of Alzheimer's disease.
Endovascular Stem Cell Therapy Promotes Neuronal Remodeling to Enhance Post Stroke Recovery by Alleviating Endoplasmic Reticulum Stress Modulated by BDNF Signaling.
Mechanism of an intramembrane chaperone for multipass membrane proteins.
Protein synthesis inhibition and loss of homeostatic functions in astrocytes from an Alzheimer's disease mouse model: a role for ER-mitochondria interaction.
Quantitative proteomics of tau and Aβ in detergent fractions from Alzheimer's disease brains.
Effects of overexpression of Hsp70 in neural stem cells on neurotoxicity and cognitive dysfunction in neonatal mice under sevoflurane exposure.
Fast-Growing Saccharomyces cerevisiae Cells with a Constitutive Unfolded Protein Response and Their Potential for Lipidic Molecule Production.
Localization matters in targeted protein degradation.
The Alzheimer's Cell Atlas (TACA): A single-cell molecular map for translational therapeutics accelerator in Alzheimer's disease.
Lipopolysaccharide distinctively alters human microglia transcriptomes to resemble microglia from Alzheimer's disease mouse models.

J Biol Chem. 2022 Oct 13. pii: S0021-9258(22)01040-7. [Epub ahead of print] 102597

Heat Shock Protein Hspa13 Regulates Endoplasmic Reticulum and Cytosolic Proteostasis Through Modulation of Protein Translocation.

Mateo F Espinoza, Khanh K Nguyen, Melody M Sycks, Ziqi Lyu, Guy M Quanrud, Maureen R Montoya, Joseph C Genereux.

  Most eukaryotic secretory proteins are co-translationally translocated through Sec61 into the endoplasmic reticulum (ER). Because these proteins have evolved to fold in the ER, their mistargeting is associated with toxicity. Genetic experiments have implicated the ER Hsp70 Hspa13/STCH as involved in processing of nascent secretory proteins. Herein, we evaluate the role of Hspa13 in protein import and the maintenance of cellular proteostasis in human cells, primarily using the HEK293T cell line. We find that Hspa13 interacts primarily with the Sec61 translocon and its associated factors. Hspa13 overexpression inhibits translocation of the secreted protein transthyretin (TTR), leading to accumulation and aggregation of immature TTR in the cytosol. ATPase-inactive mutants of Hspa13 further inhibit translocation and maturation of secretory proteins. While Hspa13 overexpression inhibits cell growth and ER quality control, we demonstrate that HSPA13 knockout destabilizes proteostasis and increases sensitivity to ER disruption. Thus, we propose that Hspa13 regulates import through the translocon to maintain both ER and cytosolic protein homeostasis. The raw mass spectrometry data associated with this manuscript has been deposited in the PRIDE archive and can be accessed at PXD033498.

Keywords:  Endoplasmic Reticulum; HSP70; Import; Molecular Chaperones; Proteostasis; Proximity Labeling; Secretion; Translocation

DOI:  https://doi.org/10.1016/j.jbc.2022.102597
Nat Commun. 2022 Oct 19. 13(1): 5889

The unfolded protein response reverses the effects of glucose on lifespan in chemically-sterilized C. elegans.

Caroline Beaudoin-Chabot, Lei Wang, Cenk Celik, Aishah Tul-Firdaus Abdul Khalid, Subhash Thalappilly, Shiyi Xu, Jhee Hong Koh, Venus Wen Xuan Lim, Ann Don Low, Guillaume Thibault.

Metabolic diseases often share common traits, including accumulation of unfolded proteins in the endoplasmic reticulum (ER). Upon ER stress, the unfolded protein response (UPR) is activated to limit cellular damage which weakens with age. Here, we show that Caenorhabditis elegans fed a bacterial diet supplemented high glucose at day 5 of adulthood (HGD-5) extends their lifespan, whereas exposed at day 1 (HGD-1) experience shortened longevity. We observed a metabolic shift only in HGD-1, while glucose and infertility synergistically prolonged the lifespan of HGD-5, independently of DAF-16. Notably, we identified that UPR stress sensors ATF-6 and PEK-1 contributed to the longevity of HGD-5 worms, while ire-1 ablation drastically increased HGD-1 lifespan. Together, we postulate that HGD activates the otherwise quiescent UPR in aged worms to overcome ageing-related stress and restore ER homeostasis. In contrast, young animals subjected to HGD provokes unresolved ER stress, conversely leading to a detrimental stress response.

DOI: https://doi.org/10.1038/s41467-022-33630-0
Front Mol Biosci. 2022 ;9 990006

Nucleosome proteostasis and histone turnover.

Adrian Arrieta, Thomas M Vondriska.

  Maintenance of protein folding homeostasis, or proteostasis is critical for cell survival as well as for execution of cell type specific biological processes such as muscle cell contractility, neuronal synapse and memory formation, and cell transition from a mitotic to post-mitotic cell type. Cell type specification is driven largely by chromatin organization, which dictates which genes are turned off or on, depending on cell needs and function. Loss of chromatin organization can have catastrophic consequences either on cell survival or cell type specific function. Chromatin organization is highly dependent on organization of nucleosomes, spatiotemporal nucleosome assembly and disassembly, and histone turnover. In this review our goal is to highlight why nucleosome proteostasis is critical for chromatin organization, how this process is mediated by histone chaperones and ATP-dependent chromatin remodelers and outline potential and established mechanisms of disrupted nucleosome proteostasis during disease. Finally, we highlight how these mechanisms of histone turnover and nucleosome proteostasis may conspire with unfolded protein response programs to drive histone turnover in cell growth and development.

Keywords:  chaperone; chromatin; development; disease; folding; histone; nucleosome

DOI:  https://doi.org/10.3389/fmolb.2022.990006
Front Plant Sci. 2022 ;13 993215

Functions of autophagy in chloroplast protein degradation and homeostasis.

Chen Wan, Qihua Ling.

  Chloroplasts are defining organelles in plant and algae, which carried out various critical metabolic processes, including photosynthesis. Roles of chloroplast protein homeostasis in plant development and stress adaptation were clearly demonstrated in previous studies, and its maintenance requires internal proteases originated from the prokaryotic ancestor. Recently, increasing evidence revealed that eukaryotic proteolytic pathways, ubiquitin-proteasome system (UPS) and autophagy, are also involved in the turnover of chloroplast proteins, in response to developmental and environmental cues. Notably, chloroplasts can be regulated via the selective degradation of chloroplast materials in a process called chlorophagy. Yet, understandings of the mechanism of chlorophagy are still rudimentary, particularly regarding its initiation and operation. Here we provide an updated overview of autophagy pathways for chloroplast protein degradation and discuss their importance for plant physiology. In addition, recent advance in analogous mitophagy in yeast and mammals will also be discussed, which provides clues for further elucidating the mechanism of chlorophagy.

Keywords:  autophagy; chlorophagy; chloroplast; mitophagy; stress response

DOI:  https://doi.org/10.3389/fpls.2022.993215
Nat Commun. 2022 Oct 21. 13(1): 6275

Single cell transcriptomic profiling of a neuron-astrocyte assembloid tauopathy model.

Hannah Drew Rickner, Lulu Jiang, Rui Hong, Nicholas K O'Neill, Chromewell A Mojica, Benjamin J Snyder, Lushuang Zhang, Dipan Shaw, Maria Medalla, Benjamin Wolozin, Christine S Cheng.

The use of iPSC derived brain organoid models to study neurodegenerative disease has been hampered by a lack of systems that accurately and expeditiously recapitulate pathogenesis in the context of neuron-glial interactions. Here we report development of a system, termed AstTau, which propagates toxic human tau oligomers in iPSC derived neuron-astrocyte assembloids. The AstTau system develops much of the neuronal and astrocytic pathology observed in tauopathies including misfolded, phosphorylated, oligomeric, and fibrillar tau, strong neurodegeneration, and reactive astrogliosis. Single cell transcriptomic profiling combined with immunochemistry characterizes a model system that can more closely recapitulate late-stage changes in adult neurodegeneration. The transcriptomic studies demonstrate striking changes in neuroinflammatory and heat shock protein (HSP) chaperone systems in the disease process. Treatment with the HSP90 inhibitor PU-H71 is used to address the putative dysfunctional HSP chaperone system and produces a strong reduction of pathology and neurodegeneration, highlighting the potential of AstTau as a rapid and reproducible tool for drug discovery.

DOI: https://doi.org/10.1038/s41467-022-34005-1
Proc Natl Acad Sci U S A. 2022 Oct 25. 119(43): e2123187119

Disruption of proteostasis causes IRE1 mediated reprogramming of alveolar epithelial cells.

Jeremy Katzen, Luis Rodriguez, Yaniv Tomer, Apoorva Babu, Ming Zhao, Aditi Murthy, Paige Carson, Matthew Barrett, Maria C Basil, Justine Carl, John P Leach, Michael Morley, Matthew D McGraw, Surafel Mulugeta, Timothy Pelura, Glenn Rosen, Edward E Morrisey, Michael F Beers.

  Disruption of alveolar type 2 cell (AEC2) protein quality control has been implicated in chronic lung diseases, including pulmonary fibrosis (PF). We previously reported the in vivo modeling of a clinical surfactant protein C (SP-C) mutation that led to AEC2 endoplasmic reticulum (ER) stress and spontaneous lung fibrosis, providing proof of concept for disruption to proteostasis as a proximal driver of PF. Using two clinical SP-C mutation models, we have now discovered that AEC2s experiencing significant ER stress lose quintessential AEC2 features and develop a reprogrammed cell state that heretofore has been seen only as a response to lung injury. Using single-cell RNA sequencing in vivo and organoid-based modeling, we show that this state arises de novo from intrinsic AEC2 dysfunction. The cell-autonomous AEC2 reprogramming can be attenuated through inhibition of inositol-requiring enzyme 1 (IRE1α) signaling as the use of an IRE1α inhibitor reduced the development of the reprogrammed cell state and also diminished AEC2-driven recruitment of granulocytes, alveolitis, and lung injury. These findings identify AEC2 proteostasis, and specifically IRE1α signaling through its major product XBP-1, as a driver of a key AEC2 phenotypic change that has been identified in lung fibrosis.

Keywords:  ER stress; quality control; surfactant protein C; transitional cell; unfolded protein response

DOI:  https://doi.org/10.1073/pnas.2123187119
Nat Commun. 2022 Oct 21. 13(1): 6271

Translational reprogramming in response to accumulating stressors ensures critical threshold levels of Hsp90 for mammalian life.

Kaushik Bhattacharya, Samarpan Maiti, Szabolcs Zahoran, Lorenz Weidenauer, Dina Hany, Diana Wider, Lilia Bernasconi, Manfredo Quadroni, Martine Collart, Didier Picard.

The cytosolic molecular chaperone Hsp90 is essential for eukaryotic life. Although reduced Hsp90 levels correlate with aging, it was unknown whether eukaryotic cells and organisms can tune the basal Hsp90 levels to alleviate physiologically accumulated stress. We have investigated whether and how mice adapt to the deletion of three out of four alleles of the two genes encoding cytosolic Hsp90, with one Hsp90β allele being the only remaining one. While the vast majority of such mouse embryos die during gestation, survivors apparently manage to increase their Hsp90β protein to at least wild-type levels. Our studies reveal an internal ribosome entry site in the 5' untranslated region of the Hsp90β mRNA allowing translational reprogramming to compensate for the genetic loss of Hsp90 alleles and in response to stress. We find that the minimum amount of total Hsp90 required to support viability of mammalian cells and organisms is 50-70% of what is normally there. Those that fail to maintain a threshold level are subject to accelerated senescence, proteostatic collapse, and ultimately death. Therefore, considering that Hsp90 levels can be reduced ≥100-fold in the unicellular budding yeast, critical threshold levels of Hsp90 have markedly increased during eukaryotic evolution.

DOI: https://doi.org/10.1038/s41467-022-33916-3
Anat Cell Biol. 2022 Oct 21.

Endothelial cell autophagy in the context of disease development.

Basheer Abdullah Marzoog.

  Endothelial cells (EC) are the anatomical boundaries between the intravascular and extravascular space. Damage to ECs is catastrophic and induces endothelial cell dysfunction. The pathogenesis is multifactorial and involves dysregulation in the signaling pathways, membrane lipids ratio disturbance, cell-cell adhesion disturbance, unfolded protein response, lysosomal and mitochondrial stress, autophagy dysregulation, and oxidative stress. Autophagy is a lysosomal-dependent turnover of intracellular components. Autophagy was recognized early in the pathogenesis of endothelial dysfunction. Autophagy is a remarkable patho (physiological) process in the cell homeostasis regulation including EC. Regulation of autophagy rate is disease-dependent and impaired with aging. Up-regulation of autophagy induces endothelial cell regeneration/differentiation and improves the function of impaired ones. The paper scrutinizes the molecular mechanisms and triggers of EC dysregulation and current perspectives for future therapeutic strategies by autophagy targeting.

Keywords:  Autophagy; Endothelial cells; Molecular medicine; Regeneration

DOI:  https://doi.org/10.5115/acb.22.098
Stem Cells Int. 2022 ;2022 2983862

Autophagy Regulates Osteogenic Differentiation of Human Periodontal Ligament Stem Cells Induced by Orthodontic Tension.

Junyi Zheng, Bowen Xu, Kai Yang.

Tooth movement is the core of orthodontics. Osteogenesis of the tension side under orthodontic force has great significance on tooth movement and stability, which involves complex mechanical and biological signal transduction. However, the mechanism remains unclear. Through in vitro cell studies, we observed the increased expression levels of osteogenesis-related factors and autophagy-related factors during the osteogenic differentiation of mesenchymal stem cells induced by orthodontic force. The change trend of autophagy-related factors and osteogenesis-related factors is similar, which indicates the involvement of autophagy in osteogenesis. In the study of autophagy-related gene ATG7 silenced cells, the expression level of autophagy was significantly inhibited, and the expression level of osteogenesis-related factors also decreased accordingly. Through drug regulation, we observed that the increase of autophagy level could effectively promote osteogenic differentiation, while the decrease of the autophagy level inhibited this process to some extent. Therefore, autophagy plays an important role in the osteogenic differentiation of mesenchymal stem cells induced by orthodontic force, which provides a novel idea useful for orthodontic treatment in promoting periodontal tissue remodeling and accelerating tooth movement.

DOI: https://doi.org/10.1155/2022/2983862
Aging Med (Milton). 2022 Sep;5(3): 182-190

A consolidated review on stem cell therapy for treatment and management of Alzheimer's disease.

Faizan Ahmad, Punya Sachdeva.

  Alzheimer's disease (AD) is one of the most common forms of dementia and affects around 50 million people around the globe. AD is diagnosed mainly through imaging techniques and to date only five drugs are approved for management of AD but no promising treatment is available for AD. So in this review, we are focusing on stem cell therapy for AD. This review will cover all stem cells like mesenchymal stem cells, embryonic stem cells, induced pluripotent stem cells, and neural stem cells. Clinical trials of AD have also been discussed. Finally, limitations of stem cells are discussed with ongoing clinical trials, and in the future stem cell therapy can be used for treatment of AD.

Keywords:  Alzheimer's disease; Induced pluripotent stem cells; embryonic stem cells; mesenchymal stem cells; neural stem cells

DOI:  https://doi.org/10.1002/agm2.12216
Stem Cell Rev Rep. 2022 Oct 17.

Endovascular Stem Cell Therapy Promotes Neuronal Remodeling to Enhance Post Stroke Recovery by Alleviating Endoplasmic Reticulum Stress Modulated by BDNF Signaling.

Harpreet Kaur, Deepaneeta Sarmah, Aishika Datta, Anupom Borah, Dileep R Yavagal, Pallab Bhattacharya.

  BACKGROUND AND PURPOSE: The impact of increased BDNF expression in brain by endovascular delivered mesenchymal stem cells (MSCs) post stroke towards modulating endoplasmic reticulum (ER) stress mediated neuronal remodeling has not been directly studied. Therefore, the present study investigates ER stress mediated neuronal remodeling following IA MSCs infusion in rodent model of ischemic stroke.METHODS: Ovariectomized Sprague Dawley rats were subjected to MCAO followed by 1 × 105 IA MSCs administration at 6 h. Infarct and functional outcomes at different time points post-stroke were evaluated. Further, various genes and protein expression studies were performed to determine the underlying mechanisms of the effect of IA MSCs towards ER stress mediated neuronal remodeling.
RESULTS: Post-stroke IA MSCs administration significantly increased BDNF expression and decreased ER stress markers expression at day 1 post-stroke. A gradual rise in the expression of growth associate protein-43 (GAP 43) and spinophilin were observed at 7, 14- and 28-days post-stroke indicating an increase in neuronal remodeling towards functional restoration.
CONCLUSIONS: The results suggest that IA MSCs post-stroke can modulate neuronal remodeling by BDNF-mediated reduction in ER stress that contribute towards functional recovery.

Keywords:  BDNF; ER stress; Intra-arterial; Mesenchymal stem cells; Neuronal remodeling

DOI:  https://doi.org/10.1007/s12015-022-10461-6
Nature. 2022 Oct 19.

Mechanism of an intramembrane chaperone for multipass membrane proteins.

Luka Smalinskaitė, Min Kyung Kim, Aaron J O Lewis, Robert J Keenan, Ramanujan S Hegde.

Multipass membrane proteins play numerous roles in biology and include receptors, transporters, ion channels and enzymes1,2. How multipass proteins are co-translationally inserted and folded at the endoplasmic reticulum is not well understood2. The prevailing model posits that each transmembrane domain (TMD) of a multipass protein successively passes into the lipid bilayer through a front-side lateral gate of the Sec61 protein translocation channel3-9. The PAT complex, an intramembrane chaperone comprising Asterix and CCDC47, engages early TMDs of multipass proteins to promote their biogenesis by an unknown mechanism10. Here, biochemical and structural analysis of intermediates during multipass protein biogenesis showed that the nascent chain is not engaged with Sec61, which is occluded and latched closed by CCDC47. Instead, Asterix binds to and redirects the substrate to a location behind Sec61, where the PAT complex contributes to a multipass translocon surrounding a semi-enclosed, lipid-filled cavity11. Detection of multiple TMDs in this cavity after their emergence from the ribosome suggests that multipass proteins insert and fold behind Sec61. Accordingly, biogenesis of several multipass proteins was unimpeded by inhibitors of the Sec61 lateral gate. These findings elucidate the mechanism of an intramembrane chaperone and suggest a new framework for multipass membrane protein biogenesis at the endopasmic reticulum.

DOI: https://doi.org/10.1038/s41586-022-05336-2
Cell Death Dis. 2022 Oct 18. 13(10): 878

Protein synthesis inhibition and loss of homeostatic functions in astrocytes from an Alzheimer's disease mouse model: a role for ER-mitochondria interaction.

Laura Tapella, Giulia Dematteis, Marianna Moro, Beatrice Pistolato, Elisa Tonelli, Virginia Vita Vanella, Daniele Giustina, Aleida La Forgia, Elena Restelli, Elettra Barberis, Tito Cali, Marisa Brini, Salvatore Villani, Erika Del Grosso, Mariagrazia Grilli, Marcello Manfredi, Marco Corazzari, Ambra A Grolla, Armando A Genazzani, Dmitry Lim.

Deregulation of protein synthesis and ER stress/unfolded protein response (ER stress/UPR) have been reported in astrocytes. However, the relationships between protein synthesis deregulation and ER stress/UPR, as well as their role in the altered homeostatic support of Alzheimer's disease (AD) astrocytes remain poorly understood. Previously, we reported that in astrocytic cell lines from 3xTg-AD mice (3Tg-iAstro) protein synthesis was impaired and ER-mitochondria distance was reduced. Here we show that impaired protein synthesis in 3Tg-iAstro is associated with an increase of p-eIF2α and downregulation of GADD34. Although mRNA levels of ER stress/UPR markers were increased two-three-fold, we found neither activation of PERK nor downstream induction of ATF4 protein. Strikingly, the overexpression of a synthetic ER-mitochondrial linker (EML) resulted in a reduced protein synthesis and augmented p-eIF2α without any effect on ER stress/UPR marker genes. In vivo, in hippocampi of 3xTg-AD mice, reduced protein synthesis, increased p-eIF2α and downregulated GADD34 protein were found, while no increase of p-PERK or ATF4 proteins was observed, suggesting that in AD astrocytes, both in vitro and in vivo, phosphorylation of eIF2α and impairment of protein synthesis are PERK-independent. Next, we investigated the ability of 3xTg-AD astrocytes to support metabolism and function of other cells of the central nervous system. Astrocyte-conditioned medium (ACM) from 3Tg-iAstro cells significantly reduced protein synthesis rate in primary hippocampal neurons. When added as a part of pericyte/endothelial cell (EC)/astrocyte 3D co-culture, 3Tg-iAstro, but not WT-iAstro, severely impaired formation and ramification of tubules, the effect, replicated by EML overexpression in WT-iAstro cells. Finally, a chemical chaperone 4-phenylbutyric acid (4-PBA) rescued protein synthesis, p-eIF2α levels in 3Tg-iAstro cells and tubulogenesis in pericyte/EC/3Tg-iAstro co-culture. Collectively, our results suggest that a PERK-independent, p-eIF2α-associated impairment of protein synthesis compromises astrocytic homeostatic functions, and this may be caused by the altered ER-mitochondria interaction.

DOI: https://doi.org/10.1038/s41419-022-05324-4
J Neurochem. 2022 Oct 21.

Quantitative proteomics of tau and Aβ in detergent fractions from Alzheimer's disease brains.

Soumya Mukherjee, Celine Dubois, Keyla Perez, Shiji Varghese, Ian E Birchall, Miranda Leckey, Natalia Davydova, Catriona McLean, Rebecca M Nisbet, Blaine R Roberts, Qiao-Xin Li, Colin L Masters, Victor A Streltsov.

  The two hallmarks of Alzheimer's disease (AD) are amyloid-β (Aβ) plaques and neurofibrillary tangles marked by phosphorylated tau. Increasing evidence suggests that aggregating Aβ drives tau accumulation, a process that involves synaptic degeneration leading to cognitive impairment. Conversely, there is a realization that non-fibrillar (oligomeric) forms of Aβ mediate toxicity in AD. Fibrillar (filamentous) aggregates of proteins across the spectrum of the primary and secondary tauopathies were the focus of recent structural studies with a filament structure based nosologic classification, but less emphasis was given to non-filamentous co-aggregates of insoluble proteins in the fractions derived from post-mortem human brains. Here, we revisited sarkosyl-soluble and -insoluble extracts to characterize tau and Aβ species by quantitative targeted mass spectrometric proteomics, biochemical assays, and electron microscopy. AD brain sarkosyl-insoluble pellets were greatly enriched with Aβ42 at almost equimolar levels to N-terminal truncated microtubule binding region (MTBR) isoforms of tau with multiple site-specific post-translational modifications (PTMs). MTBR R3 and R4 tau peptides were most abundant in the sarkosyl-insoluble materials with a 10-fold higher concentration than N-terminal tau peptides. This indicates that the major proportion of the enriched tau was the aggregation prone N-terminal and proline rich region (PRR) of truncated mixed 4R and 3R tau with more 4R than 3R isoforms. High concentration and occupancies of site-specific phosphorylation pT181 (~ 22 %) and pT217 (~ 16 %) (key biomarkers of AD) along with other PTMs in the PRR and MTBR indicated a regional susceptibility of PTMs in aggregated tau. Immunogold labelling revealed that tau may exist in globular non-filamentous form (N-terminal intact tau) co-localized with Aβ in the sarkosyl-insoluble pellets along with tau filaments (N-truncated MTBR tau). Our results suggest a model that Aβ and tau interact forming globular aggregates, from which filamentous tau and Aβ emerge. These characterizations contribute towards unravelling the sequence of events which lead to end-stage AD changes.

Keywords:  Alzheimer's disease; Aβ plaques; aducanumab; cryo-EM; immuno-EM; neurofibrillary tangles; proteomics; sarkosyl extracts; tau

DOI:  https://doi.org/10.1111/jnc.15713
Exp Brain Res. 2022 Oct 22.

Effects of overexpression of Hsp70 in neural stem cells on neurotoxicity and cognitive dysfunction in neonatal mice under sevoflurane exposure.

Yijia Chen, Yongxiang Xie, Honghu Ni.

  As one of the commonly used inhalation anesthetics in clinical practice, sevoflurane is currently widely applied in surgery for children and the elderly due to its safety and efficacy. However, the neurotoxicity and cognitive impairment induced by sevoflurane exposure cannot be ignored. A recombinant adenovirus with green fluorescent protein-labeled heat shock protein 70 (Hsp70) was constructed and used to infect neural stem cells (NSCs) separated from neonatal mice. Quantitative real-time PCR and Western blot assays were used to evaluate the expression of certain genes. 5‑Ethynyl‑2'‑deoxyuridine staining and cell counting kit assay were used to detect the proliferation and differentiation ability of NSCs. The Morris water maze experiment was used to test the cognitive abilities of mice. Adv-Hsp70 induced the overexpression of Hsp70 in mouse NSCs. Upregulation of Hsp70 promoted the proliferation ability and differentiation of mouse NSCs. NSCs that overexpressed Hsp70 attenuated sevoflurane-induced neurotoxicity and protected cognitive dysfunction in mice under sevoflurane exposure. In summary, our findings demonstrate the potential of overexpression of Hsp70 in NSCs against sevoflurane-induced impairments.

Keywords:  Anesthesia; Heat shock protein 70 (Hsp70); Neural stem cell; Sevoflurane

DOI:  https://doi.org/10.1007/s00221-022-06490-9
Appl Environ Microbiol. 2022 Oct 18. e0108322

Fast-Growing Saccharomyces cerevisiae Cells with a Constitutive Unfolded Protein Response and Their Potential for Lipidic Molecule Production.

Phuong Thi Mai Nguyen, Yuki Ishiwata-Kimata, Yukio Kimata.

  In Saccharomyces cerevisiae cells, dysfunction of the endoplasmic reticulum (ER), so-called ER stress, leads to conversion of HAC1 mRNA to the spliced form (HAC1i), which is translated into a transcription factor that drastically changes the gene expression profile. This cellular response ultimately enhances ER functions and is named the unfolded protein response (UPR). Artificial evocation of the UPR is therefore anticipated to increase productivity of beneficial materials on and in the ER. However, as demonstrated here, cells constitutively expressing HAC1i mRNA (HAC1i cells), which exhibited a strong UPR even under nonstress conditions, grew considerably slowly and frequently yielded fast-growing and low-UPR progeny. Intriguingly, growth of HAC1i cells was faster in the presence of weak ER stress that was induced by low concentrations of the ER stressor tunicamycin or by cellular expression of the ER-located version of green fluorescent protein (GFP). HAC1i cells producing ER-localized GFP stably exhibited a strong UPR activity, carried a highly expanded ER, and abundantly produced triglycerides and heterogenous carotenoids. We therefore propose that our findings provide a basis for metabolic engineering to generate cells producing valuable lipidic molecules. IMPORTANCE The UPR is thought to be a cellular response to cope with the accumulation of unfolded proteins in the ER. In S. cerevisiae cells, the UPR is severely repressed under nonstress conditions. The findings of this study shed light on the physiological significance of the tight regulation of the UPR. Constitutive UPR induction caused considerable growth retardation, which was partly rescued by the induction of weak ER stress. Therefore, we speculate that when the UPR is inappropriately induced in unstressed cells lacking aberrant ER client proteins, the UPR improperly impairs normal cellular functions. Another important point of this study was the generation of S. cerevisiae strains stably exhibiting a strong UPR activity and abundantly producing triglycerides and heterogenous carotenoids. We anticipate that our findings may be applied to produce valuable lipidic molecules using yeast cells as a potential next-generation technique.

Keywords:  Saccharomyces cerevisiae; endoplasmic reticulum; endoplasmic reticulum stress; lipid synthesis; stress response; unfolded protein response

DOI:  https://doi.org/10.1128/aem.01083-22
Cell Chem Biol. 2022 Oct 20. pii: S2451-9456(22)00354-3. [Epub ahead of print]29(10): 1465-1466

Localization matters in targeted protein degradation.

Varun Jayeshkumar Shah, Ivan Đikić.

Many factors influence the efficiency of targeted protein degradation induced by proteolysis targeting chimeras (PROTACs). In this issue of Cell Chemical Biology,Simpson et al. (2022) highlight the impact of subcellular localization. Their study elucidates that the protein of interest exhibits different amenability to PROTAC-mediated degradation at different cellular compartments.

DOI: https://doi.org/10.1016/j.chembiol.2022.09.006
Alzheimers Dement (N Y). 2022 ;8(1): e12350

The Alzheimer's Cell Atlas (TACA): A single-cell molecular map for translational therapeutics accelerator in Alzheimer's disease.

Yadi Zhou, Jielin Xu, Yuan Hou, Lynn Bekris, James B Leverenz, Andrew A Pieper, Jeffrey Cummings, Feixiong Cheng.

  Introduction: Recent advances in generating massive single-cell/nucleus transcriptomic data have shown great potential for facilitating the identification of cell type-specific Alzheimer's disease (AD) pathobiology and drug-target discovery for therapeutic development.Methods: We developed The Alzheimer's Cell Atlas (TACA) by compiling an AD brain cell atlas consisting of over 1.1 million cells/nuclei across 26 data sets, covering major brain regions (hippocampus, cerebellum, prefrontal cortex, and so on) and cell types (astrocyte, microglia, neuron, oligodendrocytes, and so on). We conducted nearly 1400 differential expression comparisons to identify cell type-specific molecular alterations (e.g., case vs healthy control, sex-specific, apolipoprotein E (APOE) ε4/ε4, and TREM2 mutations). Each comparison was followed by protein-protein interaction module detection, functional enrichment analysis, and omics-informed target and drug (over 700,000 perturbation profiles) screening. Over 400 cell-cell interaction analyses using 6000 ligand-receptor interactions were conducted to identify the cell-cell communication networks in AD.
Results: All results are integrated into TACA (https://taca.lerner.ccf.org/), a new web portal with cell type-specific, abundant transcriptomic information, and 12 interactive visualization tools for AD.
Discussion: We envision that TACA will be a highly valuable resource for both basic and translational research in AD, as it provides abundant information for AD pathobiology and actionable systems biology tools for drug discovery.
Highlights: We compiled an Alzheimer's disease (AD) brain cell atlas consisting of more than 1.1 million cells/nuclei transcriptomes from 26 data sets, covering major brain regions (cortex, hippocampus, cerebellum) and cell types (e.g., neuron, oligodendrocyte, astrocyte, and microglia).We conducted over 1400 differential expression (DE) comparisons to identify cell type-specific gene expression alterations. Major comparison types are (1) AD versus healthy control; (2) sex-specific DE, (3) genotype-driven DE (i.e., apolipoprotein E [APOE] ε4/ε4 vs APOE ε3/ε3; TREM2R47H vs common variants) analysis; and (4) others. Each comparison was further followed by (1) human protein-protein interactome network module analysis, (2) pathway enrichment analysis, and (3) gene-set enrichment analysis.For drug screening, we conducted gene set enrichment analysis for all the comparisons with over 700,000 drug perturbation profiles connecting more than 10,000 human genes and 13,000 drugs/compounds.A total of over 400 analyses of cell-cell interactions against 6000 experimentally validated ligand-receptor interactions were conducted to reveal the disease-relevant cell-cell communications in AD.

Keywords:  Alzheimer's disease; database; drug repurposing; network pathobiology; single‐cell; single‐nucleus; target identification; transcriptomics

DOI:  https://doi.org/10.1002/trc2.12350
Dis Model Mech. 2022 Oct 01. pii: dmm049349. [Epub ahead of print]15(10):

Lipopolysaccharide distinctively alters human microglia transcriptomes to resemble microglia from Alzheimer's disease mouse models.

Jimena Monzón-Sandoval, Elena Burlacu, Devika Agarwal, Adam E Handel, Liting Wei, John Davis, Sally A Cowley, M Zameel Cader, Caleb Webber.

  Alzheimer's disease (AD) is the most common form of dementia, and risk-influencing genetics implicates microglia and neuroimmunity in the pathogenesis of AD. Induced pluripotent stem cell (iPSC)-derived microglia (iPSC-microglia) are increasingly used as a model of AD, but the relevance of historical immune stimuli to model AD is unclear. We performed a detailed cross-comparison over time on the effects of combinatory stimulation of iPSC-microglia, and in particular their relevance to AD. We used single-cell RNA sequencing to measure the transcriptional response of iPSC-microglia after 24 h and 48 h of stimulation with prostaglandin E2 (PGE2) or lipopolysaccharide (LPS)+interferon gamma (IFN-γ), either alone or in combination with ATPγS. We observed a shared core transcriptional response of iPSC-microglia to ATPγS and to LPS+IFN-γ, suggestive of a convergent mechanism of action. Across all conditions, we observed a significant overlap, although directional inconsistency to genes that change their expression levels in human microglia from AD patients. Using a data-led approach, we identify a common axis of transcriptomic change across AD genetic mouse models of microglia and show that only LPS provokes a transcriptional response along this axis in mouse microglia and LPS+IFN-γ in human iPSC-microglia. This article has an associated First Person interview with the first author of the paper.

Keywords:  ATPγS; Alzheimer's disease; IFN-γ; LPS; PGE2; iPSC-microglia

DOI:  https://doi.org/10.1242/dmm.049349