bims-proarb Biomed News
on Proteostasis in aging and regenerative biology
Issue of 2022–09–11
twelve papers selected by
Rich Giadone, Harvard University



  1. Front Aging. 2022 ;3 928574
      Aging is the primary risk factor for Alzheimer's disease (AD) and related disorders (ADRDs). Tau aggregation is a hallmark of AD and other tauopathies. Even in normal aging, tau aggregation is found in brains, but in disease states, significantly more aggregated tau is present in brain regions demonstrating synaptic degeneration and neuronal loss. It is unclear how tau aggregation and aging interact to give rise to the phenotypes observed in disease states. Most AD/ADRD animal models have focused on late stages, after significant tau aggregation has occurred. There are fewer where we can observe the early aggregation events and progression during aging. In an attempt to address this gap, we created C. elegans models expressing a GFP-tagged version of the human tau protein. Here we examined how tau-gfp behaved during aging, comparing wild-type tau (hTau40), a disease-associated mutation (P301S), and an aggregation-prone variant (3PO). We measured age-dependent changes in GFP intensity and correlated those changes to normal aging in the nematode. We found differences in tau stability and accumulation depending on the tau variant expressed. hTau40GFP and P301SGFP were localized to axons and cell bodies, while 3POGFP was more concentrated within cell bodies. Expression of 3POGFP resulted in decreased lifespan and variations in locomotor rate, consistent with a pathological effect. Finally, we found that the human tau interacted genetically with the C. elegans ortholog of human tau, ptl-1, where the loss of ptl-1 significantly accelerated the time to death in animals expressing 3PO.
    Keywords:  C. elegans; microtubule associated proteins; neuronal aging; tau; tauopathy
    DOI:  https://doi.org/10.3389/fragi.2022.928574
  2. Protein Pept Lett. 2022 Sep 05.
       BACKGROUND: Alzheimer's disease (AD) is characterized by the aggregation of Tau protein and Amyloid-β peptides (Aβ 1-40 and Aβ 1-42). A loss of ribosomal population is also observed in the neurons in affected regions of AD. Our studies had demonstrated that in vitro aggregation of amyloid forming proteins, Aβ peptides and Tau protein variants (AFPs), in the vicinity of yeast 80S ribosome can induce co-aggregation of ribosomal components.
    OBJECTIVE: In this study the ability of minute quantities of AFP-ribosome co-aggregates to seed the aggregation of a large excess of untreated 80S ribosomes was explored.
    METHODS: The AFPs were purified using ion-exchange chromatography. Seeded aggregation of ribosomes in the presence of minute quantities of ribosome-protein co-aggregates or ribosomal components was studied using agarose gel electrophoretic and SDS-PAGE analysis of the pellets and Sucrose Density Gradient centrifugation of the supernatant obtained after centrifugation of the aggregation reaction mixture.
    RESULTS: Our studies therefore demonstrate that minute quantities of AFP-80S co-aggregate have significant seeding potential and could lead to aggregation of a large excess of fresh 80S ribosomes and this seeding ability is sustained over multiple cycles of ribosome aggregation. The aggregation propensity of ribosomal components alone could contribute towards seeding of ribosome aggregation.
    CONCLUSIONS: The ability of minute quantities of AFP-80S co-aggregates to seed the aggregation of large excess of fresh 80S ribosomes would result in the loss of global ribosomal population in Alzheimer's disease afflicted neurons. Hence, subject to further validation by in vivo studies, our in vitro studies indicate at a significant mode of toxicity of amyloid aggregates that might be important in Alzheimer's disease pathology.
    Keywords:  Aggregation; Alzheimer’s disease; Amyloid-β; Ribosomal RNA (rRNA); Ribosomal protein; Ribosome; Seeding; Tau protein
    DOI:  https://doi.org/10.2174/0929866529666220905112156
  3. Nat Cell Biol. 2022 Sep 08.
      While acetylated, RNA-binding-deficient TDP-43 reversibly phase separates within nuclei into complex droplets (anisosomes) comprised of TDP-43-containing liquid outer shells and liquid centres of HSP70-family chaperones, cytoplasmic aggregates of TDP-43 are hallmarks of multiple neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). Here we show that transient oxidative stress, proteasome inhibition or inhibition of the ATP-dependent chaperone activity of HSP70 provokes reversible cytoplasmic TDP-43 de-mixing and transition from liquid to gel/solid, independently of RNA binding or stress granules. Isotope labelling mass spectrometry was used to identify that phase-separated cytoplasmic TDP-43 is bound by the small heat-shock protein HSPB1. Binding is direct, mediated through TDP-43's RNA binding and low-complexity domains. HSPB1 partitions into TDP-43 droplets, inhibits TDP-43 assembly into fibrils, and is essential for disassembly of stress-induced TDP-43 droplets. A decrease in HSPB1 promotes cytoplasmic TDP-43 de-mixing and mislocalization. HSPB1 depletion was identified in spinal motor neurons of patients with ALS containing aggregated TDP-43. These findings identify HSPB1 to be a regulator of cytoplasmic TDP-43 phase separation and aggregation.
    DOI:  https://doi.org/10.1038/s41556-022-00988-8
  4. Front Pharmacol. 2022 ;13 931886
      Aging is associated with the increased risk of most age-related diseases in humans. Complanatoside A (CA) is a flavonoid compound isolated from the herbal medicine Semen Astragali Complanati. CA was reported to have potential anti-inflammatory and anti-oxidative activities. In this study, we investigated whether CA could increase the stress resistance capability and life span of Caenorhabditis elegans. Our results showed that CA could extend the longevity of C. elegans in a dosage-dependent manner, while 50 μM of CA has the best effect and increased the life span of C. elegans by about 16.87%. CA also improved the physiological functions in aging worms, such as enhanced locomotor capacity, and reduced the accumulation of the aging pigment. CA could also reduce the accumulation of toxic proteins (α-synuclein and β-amyloid) and delay the onset of neurodegenerative disorders, such as Alzheimer's disease and Parkinson's disease, in models of C. elegans. Further investigation has revealed that CA requires DAF-16/FOXO, SKN-1, and HSF-1 to extend the life span of C. elegans. CA could increase the antioxidation and detoxification activities regulated by transcription factor SKN-1 and the heat resistance by activating HSF-1 that mediated the expression of the chaperone heat shock proteins. Our results suggest that CA is a potential antiaging agent worth further research for its pharmacological mechanism and development for pharmaceutical applications.
    Keywords:  Caenorhabditis elegans; DAF-16/FOXO; aging; complanatoside A; neurodegenerative diseases; oxidative stress; proteostasis
    DOI:  https://doi.org/10.3389/fphar.2022.931886
  5. Methods Mol Biol. 2022 ;2543 155-166
      Autophagy and ER stress are most often studied employing a Western blotting approach to the measurement of autophagy by LC3B upregulation and the ER stress sensor signaling proteins PERK (protein kinase R-like endoplasmic reticulum kinase), IRE1, and ATF6 which initiate protein refolding and elongation of the ER until ER homeostasis is returned. If the misfolding of proteins is increased, then ER stress is maintained, and microautophagy of the ER or specifically reticulophagy occurs. However, LC3B, PERK, protein misfolding, and changes in ER mass (reticulophagy) can also be measured in a cell cycle-dependent manner by flow cytometry and the use of antibodies, protein misfolding, and ER tracking fluorescent probes.
    Keywords:  Autophagy; ER stress; Misfolded proteins; PERK; Reticulophagy
    DOI:  https://doi.org/10.1007/978-1-0716-2553-8_13
  6. Neurochem Res. 2022 Sep 08.
      The endoplasmic reticulum (ER) is the primary site of intracellular quality control involved in the recognition and degradation of unfolded proteins. A variety of stresses, including hypoxia and glucose starvation, can lead to accumulation of unfolded proteins triggering the ER-associated degradation (ERAD) pathway. Suppressor Enhancer Lin12/Notch1 Like (Sel1l) acts as a "gate keeper" in the quality control of de novo synthesized proteins and complexes with the ubiquitin ligase Hrd1 in the ER membrane. We previously demonstrated that ER stress-induced aberrant neural stem cell (NSC) differentiation and inhibited neurite outgrowth. Inhibition of neurite outgrowth was associated with increased Hrd1 expression; however, the contribution of Sel1l remained unclear. To investigate whether ER stress is induced during normal neuronal differentiation, we semi-quantitatively evaluated mRNA expression levels of unfolded protein response (UPR)-related genes in P19 embryonic carcinoma cells undergoing neuronal differentiation in vitro. Stimulation with all-trans retinoic acid (ATRA) for 4 days induced the upregulation of Nestin and several UPR-related genes (Atf6, Xbp1, Chop, Hrd1, and Sel1l), whereas Atf4 and Grp78/Bip were unchanged. Small-interfering RNA (siRNA)-mediated knockdown of Sel1l uncovered that mRNA levels of the neural progenitor marker Math1 (also known as Atoh1) and the neuronal marker Math3 (also known as Atoh3 and NeuroD4) were significantly suppressed at 4 days after ATRA stimulation. Consistent with this result, Sel1l silencing significantly reduced protein levels of immature neuronal marker βIII-tubulin (also known as Tuj-1) at 8 days after induction of neuronal differentiation, whereas synaptogenic factors, such as cell adhesion molecule 1 (CADM1) and SH3 and multiple ankyrin repeat domain protein 3 (Shank3) were accumulated in Sel1l silenced cells. These results indicate that neuronal differentiation triggers ER stress and suggest that Sel1l may facilitate neuronal lineage through the regulation of Math1 and Math3 expression.
    Keywords:  Endoplasmic reticulum-associated degradation (ERAD); Hrd1; Neuronal differentiation; Sel1l; Unfolded protein response (UPR)
    DOI:  https://doi.org/10.1007/s11064-022-03750-6
  7. Front Aging Neurosci. 2022 ;14 974414
      The conversion and transmission of misfolded proteins established the basis for the prion concept. Neurodegenerative diseases are considered "prion-like" disorders that lack infectivity. Among them, tauopathies are characterized by the conversion of native tau protein into an abnormally folded aggregate. During the progression of the disease, misfolded tau polymerizes into oligomers and intracellular neurofibrillary tangles (NFTs). While the toxicity of NFTs is an ongoing debate, the contribution of tau oligomers to early onset neurodegenerative pathogenesis is accepted. Tau oligomers are readily transferred from neuron to neuron propagating through the brain inducing neurodegeneration. Recently, transmission of tau oligomers via exosomes is now proposed. There is still too much to uncover about tau misfolding and propagation. Here we summarize novel findings of tau oligomers transmission and propagation via exosomes.
    Keywords:  exosomes; misfolding; prion; spreading; tau oligomers; vesicles
    DOI:  https://doi.org/10.3389/fnagi.2022.974414
  8. Biomed Pharmacother. 2022 May;pii: S0753-3322(22)00313-4. [Epub ahead of print]149 112924
      Neurodegenerative diseases are severely debilitating conditions characterized primarily by progressive neuronal loss and impairment of the nervous system. Alzheimer's and Parkinson's diseases are the most common neurodegenerative disorders, and their impact is increasing as average life expectancy increases worldwide. Although the underlying mechanisms of both progressive diseases have been extensively studied, we still lack a comprehensive understanding of the molecular basis of both diseases. Current therapeutic options do not slow the progression of the diseases and only provide symptom relief. Cell models that resemble the characteristics of the disease in question are important in drug discovery projects because they provide information about the therapeutic benefits of drugs under development. Here, we review current in vitro cell models used to study the molecular basis of Alzheimer's and Parkinson's disease focusing on their potential for discovering of disease-modifying therapeutics to combat neurodegenerative diseases. We discuss phenotypic screening as an important approach for identifying novel therapeutic molecules. Advances in the development of cell-based assays for drug discovery are discussed, ranging from simple monoculture cell models to high-throughput three-dimensional cell models. Finally, we critically present the limitations of cell models and the caveats encountered in drug discovery to find effective treatment for neurodegenerative diseases.
    Keywords:  Cell models; Cytotoxicity assays; Drug discovery; Drug screening; Neurodegenerative diseases
    DOI:  https://doi.org/10.1016/j.biopha.2022.112924
  9. Neurosci Res. 2022 Sep 05. pii: S0168-0102(22)00232-2. [Epub ahead of print]
      Alzheimer's disease (AD) is the leading cause of dementia which afflicts tens of millions of people worldwide. Despite many scientific progresses to dissect the AD's molecular basis from studies on various mouse models, it has been suffered from evolutionary species differences. Here, we report generation of a non-human primate (NHP), common marmoset model ubiquitously expressing Amyloid-beta precursor protein (APP) transgenes with the Swedish (KM670/671NL) and Indiana (V717F) mutations. The transgene integration of generated two transgenic marmosets (TG1&TG2) was thoroughly investigated by genomic PCR, whole-genome sequencing, and fluorescence in situ hybridization. By reprogramming, we confirmed the validity of transgene expression in induced neurons in vitro. Moreover, we discovered structural changes in specific brain regions of transgenic marmosets by magnetic resonance imaging analysis, including in the entorhinal cortex and hippocampus. In immunohistochemistry, we detected increased Aβ plaque-like structures in TG1 brain at 7 years old, although evident neuronal loss or glial inflammation was not observed. Thus, this study summarizes our attempt to establish an NHP AD model. Although the transgenesis approach alone seemed not sufficient to fully recapitulate AD in NHPs, it may be beneficial for drug development and further disease modeling by combination with other genetically engineered models and disease-inducing approaches.
    Keywords:  Alzheimer’s disease; common marmoset; magnetic resonance imaging; non-human primate; reprogramming; transgenesis; whole-genome sequencing
    DOI:  https://doi.org/10.1016/j.neures.2022.08.008
  10. Cell Tissue Res. 2022 Sep 07.
      Prion diseases are devastating neurodegenerative diseases caused by the structural conversion of the normally benign prion protein (PrPC) to an infectious, disease-associated, conformer, PrPSc. After decades of intense research, much is known about the self-templated prion conversion process, a phenomenon which is now understood to be operative in other more common neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. In this review, we provide the current state of knowledge concerning a relatively poorly understood aspect of prion diseases: mechanisms of neurotoxicity. We provide an overview of proposed functions of PrPC and its interactions with other extracellular proteins in the central nervous system, in vivo and in vitro models used to delineate signaling events downstream of prion propagation, the application of omics technologies, and the emerging appreciation of the role played by non-neuronal cell types in pathogenesis.
    Keywords:  Neurodegeneration; Neurotoxicity; Pathogenesis; Prion
    DOI:  https://doi.org/10.1007/s00441-022-03683-0
  11. Int J Mol Sci. 2022 Aug 25. pii: 9626. [Epub ahead of print]23(17):
      Tissue regeneration substantially relies on the functionality of tissue-resident endogenous adult stem cell populations. However, during aging, a progressive decline in organ function and regenerative capacities impedes endogenous repair processes. Especially the adult human heart is considered as an organ with generally low regenerative capacities. Interestingly, beneficial effects of systemic factors carried by young blood have been described in diverse organs including the heart, brain and skeletal muscle of the murine system. Thus, the interest in young blood or blood components as potential therapeutic agents to target age-associated malignancies led to a wide range of preclinical and clinical research. However, the translation of promising results from the murine to the human system remains difficult. Likewise, the establishment of adequate cellular models could help to study the effects of human blood plasma on the regeneration of human tissues and particularly the heart. Facing this challenge, this review describes the current knowledge of blood plasma-mediated protection and regeneration of aging tissues. The current status of preclinical and clinical research examining blood borne factors that act in stem cell-based tissue maintenance and regeneration is summarized. Further, examples of cellular model systems for a more detailed examination of selected regulatory pathways are presented.
    Keywords:  adult cardiac stem cells; blood serum; stem cell viability; tissue protection; tissue regeneration; young blood
    DOI:  https://doi.org/10.3390/ijms23179626
  12. BMC Genomics. 2022 Sep 07. 23(1): 635
       BACKGROUND: Tandem mass tag spectrometry (TMT labeling-LC-MS/MS) was utilized to examine the global proteomes of Atlantic halibut eggs at the 1-cell-stage post fertilization. Comparisons were made between eggs judged to be of good quality (GQ) versus poor quality (BQ) as evidenced by their subsequent rates of survival for 12 days. Altered abundance of selected proteins in BQ eggs was confirmed by parallel reaction monitoring spectrometry (PRM-LC-MS/MS). Correspondence of protein levels to expression of related gene transcripts was examined via qPCR. Potential mitochondrial differences between GQ and BQ eggs were assessed by transmission electron microscopy (TEM) and measurements of mitochondrial DNA (mtDNA) levels.
    RESULTS: A total of 115 proteins were found to be differentially abundant between GQ and BQ eggs. Frequency distributions of these proteins indicated higher protein folding activity in GQ eggs compared to higher transcription and protein degradation activities in BQ eggs. BQ eggs were also significantly enriched with proteins related to mitochondrial structure and biogenesis. Quantitative differences in abundance of several proteins with parallel differences in their transcript levels were confirmed in egg samples obtained over three consecutive reproductive seasons. The observed disparities in global proteome profiles suggest impairment of protein and energy homeostasis related to unfolded protein response and mitochondrial stress in BQ eggs. TEM revealed BQ eggs to contain significantly higher numbers of mitochondria, but differences in corresponding genomic mtDNA (mt-nd5 and mt-atp6) levels were not significant. Mitochondria from BQ eggs were significantly smaller with a more irregular shape and a higher number of cristae than those from GQ eggs.
    CONCLUSION: The results of this study indicate that BQ Atlantic halibut eggs are impaired at both transcription and translation levels leading to endoplasmic reticulum and mitochondrial disorders. Observation of these irregularities over three consecutive reproductive seasons in BQ eggs from females of diverse background, age and reproductive experience indicates that they are a hallmark of poor egg quality. Additional research is needed to discover when in oogenesis and under what circumstances these defects may arise. The prevalence of this suite of markers in BQ eggs of diverse vertebrate species also begs investigation.
    Keywords:  Atlantic halibut; Egg quality; Mitochondria; Mitochondrial DNA; Protein folding; Proteomics
    DOI:  https://doi.org/10.1186/s12864-022-08859-0