bims-proarb Biomed News
on Proteostasis in Aging and Regenerative Biology
Issue of 2021‒06‒13
twenty-six papers selected by
Rich Giadone
Harvard University

  1. Autophagy. 2021 Jun 10. 1-3
      Different types of autophagy co-exist in all mammalian cells, however, the specific contribution of each of these autophagic pathways to the maintenance of cellular proteostasis and cellular function remains unknown. In this work, we have investigated the consequences of failure of chaperone-mediated autophagy (CMA) in neurons and compared the impact, on the neuronal proteome, of CMA loss to that of macroautophagy loss. We found that these autophagic pathways are non-redundant and that CMA is the main one responsible for maintenance of the metastable proteome (the one at risk of aggregation). We demonstrate that loss of CMA, as the one that occurs in aging, has a synergistic effect with the proteotoxicity associated with neurodegenerative conditions such as Alzheimer disease (AD) and, conversely, that, pharmacological enhancement of CMA is effective in improving both behavior and pathology in two different AD mouse models.
    Keywords:  Alzheimer disease; chaperones; chemical activators of autophagy; lysosomes; metastable proteome; neurodegeneration; protein aggregation; proteostasis; tau; tauopathies
  2. Eur J Pharmacol. 2021 Jun 08. pii: S0014-2999(21)00402-7. [Epub ahead of print] 174249
      Endoplasmic reticulum (ER) stress plays a critical role in progression of diabetes and development of complications, notably cardiovascular disease. Some of the contemporary anti-hyperglycemic drugs have been shown to inhibit ER stress. To extend these observations, the effects of various anti-hyperglycemic agents were screened for their effects on ER stress. Seven classes of anti-hyperglycemic drugs were screened including sulfonylureas, meglitinides, metformin, α glucosidase inhibitors, thiazolidinedione, glucagon like peptide 1 (GLP-1) receptor agonists and sodium-glucose cotransporter 2 (SGLT-2) inhibitors. ER stress was measured in human coronary artery endothelial cells (HCAEC) either treated with tunicamycin (TM) or cultured in hyperglycemic conditions (27.5 mM dextrose). The ER stress was measured with the secreted alkaline phosphatase (ES-TRAP) assay. Mediators of the unfolded protein response, including activating transcription factor 6 (ATF6), glucose-regulated protein 78 (GRP78), phospho-inositol-requiring enzyme 1α (pIRE1α), IRE1α, phospho-protein kinase R (PKR)-like endoplasmic reticulum kinase (pPERK), and PERK were measured by Western blot. Metformin, GLP-1 receptor agonists (GLP-1, exendin 4, liraglutide, albiglutide, and lixisenatide) and SGLT-2 inhibitors (canagliflozin, dapagliflozin, and empagliflozin) were the only anti-hyperglycemic drugs screened that reduced ER stress caused by pharmacological (tunicamycin) or hyperglycemic conditions. High-dextrose and TM increased IRE1α and PERK phosphorylation and ATF6 and GRP78 expression, while treatment with metformin, liraglutide (a GLP-1 receptor agonist) and dapagliflozin (a SGLT-2 inhibitor), suppressed IRE1α and PERK phosphorylation as well as ATF6 and GRP78 expression. The cardioprotective effects of metformin, some of the GLP-1 receptor agonists and SGLT2 inhibitors may be partly related to their ability to reduce ER stress.
    Keywords:  GLP-1; HCAEC; unfolded protein response
  3. Cell Rep. 2021 Jun 08. pii: S2211-1247(21)00568-4. [Epub ahead of print]35(10): 109217
      The ubiquitous ribosome-associated complex (RAC) is a chaperone that spans ribosomes, making contacts near both the polypeptide exit tunnel and the decoding center, a position prime for sensing and coordinating translation and folding. Loss of RAC is known to result in growth defects and sensitization to translational and osmotic stresses. However, the physiological substrates of RAC and the mechanism(s) by which RAC is involved in responding to specific stresses in higher eukaryotes remain obscure. The data presented here uncover an essential function of mammalian RAC in the unfolded protein response (UPR). Knockdown of RAC sensitizes mammalian cells to endoplasmic reticulum (ER) stress and selectively interferes with IRE1 branch activation. Higher-order oligomerization of the inositol-requiring enzyme 1α (IRE1α) kinase/endoribonuclease depends upon RAC. These results reveal a surveillance function for RAC in the UPR, as follows: modulating IRE1α clustering as required for endonuclease activation and splicing of the substrate Xbp1 mRNA.
    Keywords:  IRE1 foci; UPR; Xbp1 mRNA; chaperone; ribosome stalling; ribosome-associated complex; translation
  4. Cell Death Differ. 2021 Jun 07.
      Tightly orchestrated programmed cell death (PCD) signalling events occur during normal neuronal development in a spatially and temporally restricted manner to establish the neural architecture and shaping the CNS. Abnormalities in PCD signalling cascades, such as apoptosis, necroptosis, pyroptosis, ferroptosis, and cell death associated with autophagy as well as in unprogrammed necrosis can be observed in the pathogenesis of various neurological diseases. These cell deaths can be activated in response to various forms of cellular stress (exerted by intracellular or extracellular stimuli) and inflammatory processes. Aberrant activation of PCD pathways is a common feature in neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS), Alzheimer's disease, Parkinson's disease, and Huntington's disease, resulting in unwanted loss of neuronal cells and function. Conversely, inactivation of PCD is thought to contribute to the development of brain cancers and to impact their response to therapy. For many neurodegenerative diseases and brain cancers current treatment strategies have only modest effect, engendering the need for investigations into the origins of these diseases. With many diseases of the brain displaying aberrations in PCD pathways, it appears that agents that can either inhibit or induce PCD may be critical components of future therapeutic strategies. The development of such therapies will have to be guided by preclinical studies in animal models that faithfully mimic the human disease. In this review, we briefly describe PCD and unprogrammed cell death processes and the roles they play in contributing to neurodegenerative diseases or tumorigenesis in the brain. We also discuss the interplay between distinct cell death signalling cascades and disease pathogenesis and describe pharmacological agents targeting key players in the cell death signalling pathways that have progressed through to clinical trials.
  5. Front Mol Biosci. 2021 ;8 671458
      Tauopathies are a heterogenous family of progressive neurodegenerative diseases defined by the appearance of proteinaceous lesions within the brain composed of abnormally folded species of Microtubule Associated Protein Tau (tau). Alzheimer's Disease (AD), the most common tauopathy, is the leading cause of cognitive decline among the elderly and is responsible for more than half of all cases of senile dementia worldwide. The characteristic pathology of many tauopathies-AD included-presents as Neurofibrillary Tangles (NFTs), insoluble inclusions found within the neurons of the central nervous system composed primarily of tau protein arranged into Paired Helical Fibrils (PHFs). The spatial extent of this pathology evolves in a remarkably consistent pattern over the course of disease progression. Among the leading hypotheses which seek to explain the stereotypical progression of tauopathies is the prion model, which proposes that the spread of tau pathology is mediated by the transmission of self-propagating tau conformers between cells in a fashion analogous to the mechanism of communicable prion diseases. Protein-glycan interactions between tau and Heparan Sulfate Proteoglycans (HSPGs) have been implicated as a key facilitator in each stage of the prion-like propagation of tau pathology, from the initial secretion of intracellular tau protein into the extracellular matrix, to the uptake of pathogenic tau seeds by cells, and the self-assembly of tau into higher order aggregates. In this review we outline the biochemical basis of the tau-HS interaction and discuss our current understanding of the mechanisms by which these interactions contribute to the propagation of tau pathology in tauopathies, with a particular focus on AD.
    Keywords:  2-O and 6-O sulfated heparins; 3-O sulfation; Alzheimer’s disease; glycobiology; heparan sulfate; neurodegenerative diseases; prions and prion disease; tauopathies
  6. Front Bioeng Biotechnol. 2021 ;9 672594
      The prevalence of the two most common neurodegenerative diseases, Parkinson's disease (PD) and Alzheimer's Disease (AD), are expected to rise alongside the progressive aging of society. Both PD and AD are classified as proteinopathies with misfolded proteins α-synuclein, amyloid-β, and tau. Emerging evidence suggests that these misfolded aggregates are prion-like proteins that induce pathological cell-to-cell spreading, which is a major driver in pathogenesis. Additional factors that can further affect pathology spreading include oxidative stress, mitochondrial damage, inflammation, and cell death. Nanomaterials present advantages over traditional chemical or biological therapeutic approaches at targeting these specific mechanisms. They can have intrinsic properties that lead to a decrease in oxidative stress or an ability to bind and disaggregate fibrils. Additionally, nanomaterials enhance transportation across the blood-brain barrier, are easily functionalized, increase drug half-lives, protect cargo from immune detection, and provide a physical structure that can support cell growth. This review highlights emergent nanomaterials with these advantages that target oxidative stress, the fibrillization process, inflammation, and aid in regenerative medicine for both PD and AD.
    Keywords:  Alzheimer’s disease; Parkinson’s disease; nanotechnology/nanomaterials; nanozymes; oxidative stress
  7. J Biol Chem. 2021 Jun 05. pii: S0021-9258(21)00660-8. [Epub ahead of print] 100860
      Formation of biomolecular condensates through liquid-liquid phase separation (LLPS) has been described for several pathogenic proteins linked to neurodegenerative diseases and is discussed as an early step in the formation of protein aggregates with neurotoxic properties. In prion diseases, neurodegeneration and formation of infectious prions is caused by aberrant folding of the cellular prion protein (PrPC). PrPC is characterized by a large intrinsically disordered N-terminal domain and a structured C-terminal globular domain. A significant fraction of mature PrPC is proteolytically processed in vivo into an entirely unstructured fragment, designated N1, and the corresponding C-terminal fragment C1 harboring the globular domain. Notably, N1 contains a polybasic motif that serves as a binding site for neurotoxic Aβ oligomers. PrP can undergo LLPS, however, nothing is known how phase separation of PrP is triggered on a molecular scale. Here we show that the intrinsically disordered N1 domain is necessary and sufficient for LLPS of PrP. Similarly to full-length PrP, the N1 fragment formed highly dynamic liquid-like droplets. Remarkably, a slightly shorter unstructured fragment, designated N2, which lacks the Aβ-binding domain and is generated under stress conditions, failed to form liquid-like droplets and instead formed amorphous assemblies of irregular structure. Through a mutational analysis we identified three positively charged lysines in the post-octarepeat region as essential drivers of condensate formation, presumably largely via cation-π interactions. These findings provide insights into the molecular basis of liquid-liquid phase separation of the mammalian prion protein and reveal a crucial role of the Aβ-binding domain in this process.
    Keywords:  aggregation; intrinsically disordered protein; liquid-liquid phase separation; neurodegenerative disease; prion disease; prion protein; protein self-assembly
  8. Eur J Pharmacol. 2021 Jun 08. pii: S0014-2999(21)00400-3. [Epub ahead of print] 174247
      Endoplasmic reticulum (ER) stress is an inflammatory response that contributes to endothelial dysfunction, a hallmark of cardiovascular diseases, in close interplay with oxidative stress. Recently, Sestrin2 (SESN2) emerged as a novel stress-inducible protein protecting cells from oxidative stress. We investigated here, for the first time, the impact of SESN2 suppression on oxidative stress and cell survival in human endothelial cells subjected to pharmacologically (thapsigargin)-induced ER stress and studied the underlying cellular pathways. We found that SESN2 silencing, though did not specifically induce ER stress, it aggravated the effects of thapsigargin-induced ER stress on oxidative stress and cell survival. This was associated with a dysregulation of Nrf-2, AMPK and mTORC1 signaling pathways. Furthermore, SESN2 silencing aggravated, in an additive manner, apoptosis caused by thapsigargin. Importantly, SESN2 silencing, unlike thapsigargin, caused a dramatic decrease in protein expression and phosphorylation of Akt, a critical pro-survival hub and component of the AMPK/Akt/mTORC1 axis. Our findings suggest that patients with conditions characterized by ER stress activation, such as diabetes, may be at higher risk for cardiovascular complications if their endogenous ability to stimulate and/or maintain expression levels of SESN2 is disturbed or impaired. Therefore, identifying novel or repurposing existing pharmacotherapies to enhance and/or maintain SESN2 expression levels would be beneficial in these conditions.
    Keywords:  Cardiovascular disease; Sestrin2; cell survival; endoplasmic reticulum (ER) stress; endothelial dysfunction; oxidative stress
  9. Autophagy. 2021 Jun 08. 1-14
      Macroautophagy/autophagy is emerging as a major pathway that regulates both aging and stem cell function. Previous studies have demonstrated a positive correlation of autophagy with longevity; however, these studies did not directly address the consequence of altered autophagy in stem cells during aging. In this study, we used Becn1F121A/F121A knockin mice (designated as Becn1 KI mice) with the F121A allele in the autophagy gene Becn1 to investigate the consequences of enhanced autophagy in postnatal neural stem cells (NSCs) during aging. We found that increased autophagy protected NSCs from exhaustion and promoted neurogenesis in old (≥18-months-old) mice compared with age-matched wild-type (WT) mice, although it did not affect NSCs in young (3-months-old) mice. After pharmacologically-induced elimination of proliferative cells in the subventricular zone (SVZ), there was enhanced re-activation of quiescent NSCs in old Becn1 KI mice as compared to those in WT mice, with more efficient exit from quiescent status to generate proliferative cells and neuroblasts. Moreover, there was also improved maintenance and increased neuronal differentiation of NSCs isolated from the SVZ of old Becn1 KI mice in in vitro assays. Lastly, the increased neurogenesis in Becn1 KI mice was associated with better olfactory function in aged animals. Together, our results suggest a protective role of increased autophagy in aging NSCs, which may help the development of novel strategies to treat age-related neurodegeneration.
    Keywords:  Aging; beclin 1 mutant mouse; increased autophagy; neural stem cells; neurogenesis; self-renewal
  10. DNA Repair (Amst). 2021 Jun 08. pii: S1568-7864(21)00111-7. [Epub ahead of print]105 103155
      The accumulation of unrepaired DNA lesions is associated with many pathological outcomes in humans, particularly in neurodegenerative diseases and in normal aging. Evidence supporting a causal role for DNA damage in the onset and progression of neurodegenerative disease has come from rare human patients with mutations in DNA damage response genes as well as from model organisms; however, the generality of this relationship in the normal population is unclear. In addition, the relevance of DNA damage in the context of proteotoxic stress-the widely accepted paradigm for pathology during neurodegeneration-is not well understood. Here, observations supporting intertwined roles of DNA damage and proteotoxicity in aging-related neurological outcomes are reviewed, with particular emphasis on recent insights into the relationships between DNA repair and autophagy, the ubiquitin proteasome system, formation of protein aggregates, poly-ADP-ribose polymerization, and transcription-driven DNA lesions.
    Keywords:  DNA repair; Neurodegeneration; PARP; Protein aggregation; Protein homeostasis
  11. Front Behav Neurosci. 2021 ;15 634157
      Hyperphosphorylation and the subsequent aggregation of tau protein into neurofibrillary tangles (NFTs) are well-established neuropathological hallmarks of Alzheimer's disease (AD) and associated tauopathies. To further examine the impact and progression of human tau pathology in neurodegenerative contexts, the humanized tau (htau) mouse model was originally created. Despite AD-like tau pathological features recapitulated in the htau mouse model, robustness of behavioral phenotypes has not been fully established. With the ultimate goal of evaluating the htau mouse model as a candidate for testing AD therapeutics, we set out to verify, in-house, the presence of robust, replicable cognitive deficits in the htau mice. The present study shows behavioral data collected from a carefully curated battery of learning and memory tests. Here we report a significant short-term spatial memory deficit in aged htau mice, representing a novel finding in this model. However, we did not find salient impairments in long-term learning and memory previously reported in this mouse model. Here, we attempted to understand the discrepancies in the literature by highlighting the necessity of scrutinizing key procedural differences across studies. Reported cognitive deficits in the htau model may depend on task difficulty and other procedural details. While the htau mouse remains a unique and valuable animal model for replicating late onset AD-like human tau pathology, its cognitive deficits are modest under standard testing conditions. The overarching message is that before using any AD mouse model to evaluate treatment efficacies, it is imperative to first characterize and verify the presence of behavioral deficits in-house.
    Keywords:  Alzheimer’s disease; cognition; mouse model; neurodegeneration; spatial memory; tau pathology
  12. Cell Death Dis. 2021 Jun 08. 12(6): 592
      Stress granules (SGs) are membraneless cell compartments formed in response to different stress stimuli, wherein translation factors, mRNAs, RNA-binding proteins (RBPs) and other proteins coalesce together. SGs assembly is crucial for cell survival, since SGs are implicated in the regulation of translation, mRNA storage and stabilization and cell signalling, during stress. One defining feature of SGs is their dynamism, as they are quickly assembled upon stress and then rapidly dispersed after the stress source is no longer present. Recently, SGs dynamics, their components and their functions have begun to be studied in the context of human diseases. Interestingly, the regulated protein self-assembly that mediates SG formation contrasts with the pathological protein aggregation that is a feature of several neurodegenerative diseases. In particular, aberrant protein coalescence is a key feature of polyglutamine (PolyQ) diseases, a group of nine disorders that are caused by an abnormal expansion of PolyQ tract-bearing proteins, which increases the propensity of those proteins to aggregate. Available data concerning the abnormal properties of the mutant PolyQ disease-causing proteins and their involvement in stress response dysregulation strongly suggests an important role for SGs in the pathogenesis of PolyQ disorders. This review aims at discussing the evidence supporting the existence of a link between SGs functionality and PolyQ disorders, by focusing on the biology of SGs and on the way it can be altered in a PolyQ disease context.
  13. Drug Des Devel Ther. 2021 ;15 2385-2399
      Purpose: Many researches have investigated the functions of tetramethylpyrazine (TMP) in Alzheimer's disease (AD). This study aimed to discuss the underlying mechanism of TMP in AD mice.Methods: TMP (200 mg/kg) was administered to 6-month-old APP/PS1 transgenic mice, and behavioral changes and hippocampal nerve injury in AD mice were detected. Apoptosis and autophagy-related protein levels were detected. Changes in gene expression before and after TMP treatment were compared using transcriptome sequencing. The effects of Cullin 4B (CUL4B) overexpression and somatostatin receptor 4 (SSTR4) silencing on AD symptoms and SSTR4 ubiquitination in APP/PS1 mice were observed. SH-SY5Y and PC12 cells were treated with 25 μmol/L Aβ25-35 and TMP to observe cell viability, apoptosis, and autophagy. Cell viability and apoptosis were measured again after treatment with proteasome inhibitor MG132 or lysosomal inhibitor 3-mA.
    Results: TMP treatment improved the behavioral cognition of APP/PS1 mice and improved the neuronal apoptosis and damage in brain tissue. CUL4B was significantly upregulated in APP/PS1 mouse brain tissue, and SSRT4 protein was downregulated, and the levels of CUL4B and SSRT4 were negatively correlated. TMP treatment downregulated CUL4B, inhibited SSRT4 ubiquitination and upregulated SSRT4 protein level in APP/PS1 mouse brain tissue, while CUL4B overexpression or SSRT4 silencing reversed the effect of TMP. TMP and MG132 improved the decreased activity, increased apoptosis and increased SSRT4 protein in SH-SY5Y and PC12 cells treated with Aβ25-35, but not 3-mA. CUL4B overexpression promoted the ubiquitination of SSTR4 in cells, which partially reversed the effect of TMP.
    Conclusion: TMP could improve the cognitive ability of AD mice by inhibiting CUL4B expression and the ubiquitination degradation of SSTR, and alleviating neuronal apoptosis and injury. This study may offer a new therapeutic option for AD treatment.
    Keywords:  Alzheimer disease; Cullin 4B; somatostatin receptor 4; tetramethylpyrazine; ubiquitination
  14. Cell Mol Bioeng. 2021 Jun;14(3): 231-240
      Introduction: Cell chirality is an intrinsic cellular property that determines the directionality of cellular polarization along the left-right axis. We recently show that endothelial cell chirality can influence intercellular junction formation and alter trans-endothelial permeability, depending on the uniformity of the chirality of adjacent cells, which suggests a potential role for cell chirality in neurodegenerative diseases with blood-brain barrier (BBB) dysfunctions, such as Alzheimer's disease (AD). In this study, we determined the effects of AD-related proteins amyloid-β (Aβ), tau, and apolipoprotein E4 (ApoE4) on the chiral bias of the endothelial cell component in BBB.Methods: We first examined the chiral bias and effects of protein kinase C (PKC)-mediated chiral alterations of human brain microvascular endothelial cells (hBMECs) using the ring micropattern chirality assay. We then investigated the effects of Aβ, tau, and ApoE4 on hBMEC chirality using chirality assay and biased organelle positions.
    Results: The hBMECs have a strong clockwise chiral bias, which can be reversed by protein kinase C (PKC) activation. Treatment with tau significantly disrupted the chiral bias of hBMECs with altered cellular polarization. In contrast, neither ApoE4 nor Aβ-42 caused significant changes in cell chirality.
    Conclusions: We conclude that tau might cause BBB dysfunction by disrupting cell polarization and chiral morphogenesis, while the effects of ApoE4 and Aβ-42 on BBB integrity might be chirality-independent. The potential involvement of chiral morphogenesis in tau-mediated BBB dysfunction in AD provides a novel perspective in vascular dysfunction in tauopathies such as AD, chronic traumatic encephalopathy, progressive supranuclear palsy, and frontotemporal dementia.
    Supplementary Information: The online version contains supplementary material available at 10.1007/s12195-021-00669-w.
    Keywords:  Alzheimer’s disease; Amyloid-β; Apolipoprotein E4; Blood–brain barrier; Cell chirality; Tau
  15. Neurochem Int. 2021 Jun 04. pii: S0197-0186(21)00139-X. [Epub ahead of print] 105093
      Inhibition of endoplasmic reticulum (ER) stress reduces blood-brain barrier (BBB) injury caused by ischemia/reperfusion (I/R), with indistinct mechanisms. Salvinorin A (SA) relieves I/R-induced BBB leakage; however, whether it is related to the suppression of ER stress is yet unclear. To address this question, we have used both a rat model of middle cerebral artery occlusion (MCAO) and human brain microvascular endothelial cells (HBMECs) with oxygen-glucose deprivation (OGD). SA was injected by tail vein at the terminal of ischemia; Norbinaltorphimine(NB), a kappa opioid antagonist, was administered 30 min prior to SA; 4-phenylbutyric acid(4-PBA), an ER stress inhibitor, was injected intraperitoneally after the onset of ischemia; adenylate-activated protein kinase (AMPK)-specific small interfering RNAs (siRNAs) were transfected to HBMECs before OGD. The assessment was as follows: infarct volume, brain water gain, Evans blue leakage, and modified neurological severity score (mNSS) after MCAO; HBMECs apoptosis rate and permeability, ER stress-related protein, and reactive oxygen species (ROS) and calcium levels after OGD. The results showed that SA significantly reduced the BBB leakage in vivo; SA relieved the apoptotic rates and ER stress in HBMECs, protected the permeability of HBMECs, and reduced ROS and calcium ion level after OGD. Moreover, the SA function was blocked by NB in vivo and AMPK- siRNAs in vitro. We conclude that SA mitigated BBB damage and HBMEC injury after I/R and alleviated ER stress in endothelial cells via AMPK pathway.
    Keywords:  Salvinorin A; blood-brain barrier; endoplasmic reticulum stress; endothelial cells; stroke
  16. Proc Natl Acad Sci U S A. 2021 Jun 15. pii: e2025053118. [Epub ahead of print]118(24):
      TANK-binding kinase 1 (TBK1) is a multifunctional kinase with an essential role in mitophagy, the selective clearance of damaged mitochondria. More than 90 distinct mutations in TBK1 are linked to amyotrophic lateral sclerosis (ALS) and fronto-temporal dementia, including missense mutations that disrupt the abilities of TBK1 to dimerize, associate with the mitophagy receptor optineurin (OPTN), autoactivate, or catalyze phosphorylation. We investigated how ALS-associated mutations in TBK1 affect Parkin-dependent mitophagy using imaging to dissect the molecular mechanisms involved in clearing damaged mitochondria. Some mutations cause severe dysregulation of the pathway, while others induce limited disruption. Mutations that abolish either TBK1 dimerization or kinase activity were insufficient to fully inhibit mitophagy, while mutations that reduced both dimerization and kinase activity were more disruptive. Ultimately, both TBK1 recruitment and OPTN phosphorylation at S177 are necessary for engulfment of damaged mitochondra by autophagosomal membranes. Surprisingly, we find that ULK1 activity contributes to the phosphorylation of OPTN in the presence of either wild-type or kinase-inactive TBK1. In primary neurons, TBK1 mutants induce mitochondrial stress under basal conditions; network stress is exacerbated with further mitochondrial insult. Our study further refines the model for TBK1 function in mitophagy, demonstrating that some ALS-linked mutations likely contribute to disease pathogenesis by inducing mitochondrial stress or inhibiting mitophagic flux. Other TBK1 mutations exhibited much less impact on mitophagy in our assays, suggesting that cell-type-specific effects, cumulative damage, or alternative TBK1-dependent pathways such as innate immunity and inflammation also factor into the development of ALS in affected individuals.
    Keywords:  OPTN; Parkin; TBK1; mitophagy; neurodegeneration
  17. Neuroreport. 2021 Jun 07.
      Leptin plays an important role in energy intake and body weight homeostasis. Leptin is secreted mainly from white adipose tissue and circulates in the bloodstream, inhibiting food intake by activating the leptin receptor expressed on hypothalamic neurons. Recent studies have demonstrated leptin resistance as the main factor involved in the development of obesity. We and others have reported that leptin resistance is caused by endoplasmic reticulum (ER) stress due to the accumulation of unfolded protein in the ER. In the present study, we investigated whether isoflavones could affect ER stress and the subsequent development of leptin resistance. We showed that biochanin A, a family of isoflavones, strongly attenuated cell death induced by ER stress in neuronal cells, improved ER stress-induced impairments in leptin signaling, and suppressed ER stress-induced expression of glucose-regulated protein 78. These results suggest that biochanin A may have pharmacological properties that can ameliorate leptin resistance by reducing ER stress.
  18. Adv Protein Chem Struct Biol. 2021 ;pii: S1876-1623(21)00017-1. [Epub ahead of print]126 227-278
      Proteins have evolved in specific 3D structures and play different functions in cells and determine various reactions and pathways. The newly synthesized amino acid chains once depart ribosome must crumple into three-dimensional structures so can be biologically active. This process of protein that makes a functional molecule is called protein folding. The protein folding is both a biological and a physicochemical process that depends on the sequence of it. In fact, this process occurs more complicated and in some cases and in exposure to some molecules like glucose (glycation), mistaken folding leads to amyloid structures and fatal disorders called conformational diseases. Such conditions are detected by the quality control system of the cell and these abnormal proteins undergo renovation or degradation. This scenario takes place by the chaperones, chaperonins, and Ubiquitin-proteasome complex. Understanding of protein folding mechanisms from different views including experimental and computational approaches has revealed some intermediate ensembles such as molten globule and has been subjected to biophysical and molecular biology attempts to know more about prevalent conformational diseases.
    Keywords:  Amyloid structure; Biophysical techniques; Biothermodynamics; Conformational diseases; Folding mechanisms; Molecular chaperons; Molten globule; Neurodegenerative diseases; Protein folding
  19. Oxid Med Cell Longev. 2021 ;2021 6617256
      Mitochondria are multifaceted organelles that serve to power critical cellular functions, including act as power generators of the cell, buffer cytosolic calcium overload, production of reactive oxygen species, and modulating cell survival. The structure and the cellular location of mitochondria are critical for their function and depend on highly regulated activities such as mitochondrial quality control (MQC) mechanisms. The MQC is regulated by several sets of processes: mitochondrial biogenesis, mitochondrial fusion and fission, mitophagy, and other mitochondrial proteostasis mechanisms such as mitochondrial unfolded protein response (mtUPR) or mitochondrial-derived vesicles (MDVs). These processes are important for the maintenance of mitochondrial homeostasis, and alterations in the mitochondrial function and signaling are known to contribute to the dysregulation of cell death pathways. Recent studies have uncovered regulatory mechanisms that control the activity of the key components for mitophagy. In this review, we discuss how mitophagy is controlled and how mitophagy impinges on health and disease through regulating cell death.
  20. Ageing Res Rev. 2021 Jun 08. pii: S1568-1637(21)00135-5. [Epub ahead of print] 101388
      Inside and outside the brain, accumulation of amyloid fibrils plays key roles in the pathogenesis of fatal age-related diseases such as Alzheimer's and Parkinson's diseases and wild-type transthyretin amyloidosis. Although the incidence of all amyloidoses increases with age, for some types of amyloidosis aging is known as the main direct risk factor, and these types are typically diseases of elderly people. More than 10 different precursor proteins are known to cause age-associated amyloidosis; these proteins include amyloid β protein, α-synuclein, transthyretin, islet amyloid polypeptide, atrial natriuretic factor, and the newly discovered epidermal growth factor-containing fibulin-like extracellular matrix protein 1. Except for intracerebral amyloidoses, most age-related amyloidoses have been little studied. Indeed, in view of the increasing life expectancy in our societies, understanding how aging is involved in the process of amyloid fibril accumulation and the effects of amyloid deposits on the aging body is extremely important. In this review, we summarize current knowledge about the nature of amyloid precursor proteins; the prevalence, clinical manifestations, and pathogenesis of amyloidosis; and recent advances in our understanding of age-related amyloidoses outside the brain.
    Keywords:  Aging; Amyloid; Amyloidosis; Epidermal growth factor-containing fibulin-like extracellular matrix protein 1; Islet amyloid polypeptide; Transthyretin
  21. Commun Biol. 2021 Jun 08. 4(1): 703
      Random errors in protein synthesis are prevalent and ubiquitous, yet their effect on organismal health has remained enigmatic for over five decades. Here, we studied whether mice carrying the ribosomal ambiguity (ram) mutation Rps2-A226Y, recently shown to increase the inborn error rate of mammalian translation, if at all viable, present any specific, possibly aging-related, phenotype. We introduced Rps2-A226Y using a Cre/loxP strategy. Resulting transgenic mice were mosaic and showed a muscle-related phenotype with reduced grip strength. Analysis of gene expression in skeletal muscle using RNA-Seq revealed transcriptomic changes occurring in an age-dependent manner, involving an interplay of PGC1α, FOXO3, mTOR, and glucocorticoids as key signaling pathways, and finally resulting in activation of a muscle atrophy program. Our results highlight the relevance of translation accuracy, and show how disturbances thereof may contribute to age-related pathologies.
  22. FASEB J. 2021 Jul;35(7): e21727
      We previously discovered the implication of membrane-type 5-matrix metalloproteinase (MT5-MMP) in Alzheimer's disease (AD) pathogenesis. Here, we shed new light on pathogenic mechanisms by which MT5-MMP controls the processing of amyloid precursor protein (APP) and the fate of amyloid beta peptide (Aβ) as well as its precursor C99, and C83. We found in human embryonic kidney cells (HEK) carrying the APP Swedish familial mutation (HEKswe) that deleting the C-terminal non-catalytic domains of MT5-MMP hampered its ability to process APP and release the soluble 95 kDa form (sAPP95). Catalytically inactive MT5-MMP variants increased the levels of Aβ and promoted APP/C99 sorting in the endolysosomal system, likely through interactions of the proteinase C-terminal portion with C99. Most interestingly, the deletion of the C-terminal domain of MT5-MMP caused a strong degradation of C99 by the proteasome and prevented Aβ accumulation. These discoveries reveal new control of MT5-MMP over APP by proteolytic and non-proteolytic mechanisms driven by the C-terminal domains of the proteinase. The targeting of these non-catalytic domains of MT5-MMP could, therefore, provide new insights into the therapeutic regulation of APP-related pathology in AD.
    Keywords:  amyloid beta precursor protein; endosome; metalloproteinase; proteasome; secretase
  23. Neural Regen Res. 2022 Jan;17(1): 31-37
      The presenilin genes (PSEN1 and PSEN2) are mainly responsible for causing early-onset familial Alzheimer's disease, harboring ~300 causative mutations, and representing ~90% of all mutations associated with a very aggressive disease form. Presenilin 1 is the catalytic core of the γ-secretase complex that conducts the intramembranous proteolytic excision of multiple transmembrane proteins like the amyloid precursor protein, Notch-1, N- and E-cadherin, LRP, Syndecan, Delta, Jagged, CD44, ErbB4, and Nectin1a. Presenilin 1 plays an essential role in neural progenitor maintenance, neurogenesis, neurite outgrowth, synaptic function, neuronal function, myelination, and plasticity. Therefore, an imbalance caused by mutations in presenilin 1/γ-secretase might cause aberrant signaling, synaptic dysfunction, memory impairment, and increased Aβ42/Aβ40 ratio, contributing to neurodegeneration during the initial stages of Alzheimer's disease pathogenesis. This review focuses on the neuronal differentiation dysregulation mediated by PSEN1 mutations in Alzheimer's disease. Furthermore, we emphasize the importance of Alzheimer's disease-induced pluripotent stem cells models in analyzing PSEN1 mutations implication over the early stages of the Alzheimer's disease pathogenesis throughout neuronal differentiation impairment.
    Keywords:  Notch; PSEN1; familial Alzheimer’s disease; familial Alzheimer’s disease-induced pluripotent stem cells models; induced pluripotent stem cells; mutations; neurogenesis; neuronal differentiation; presenilin 1; γ-secretase complex
  24. J Cell Physiol. 2021 Jun 08.
      Hematopoietic stem cells (HSCs) are particularly characterized by their quiescence and self-renewal. Cell cycle regulators tightly control quiescence and self-renewal capacity. Studies suggest that modulation of ubiquitination and neddylation could contribute to HSC function via cyclin-dependent kinase inhibitors (CDKIs). S-phase kinase-associated protein 2 (SKP2) is responsible for ubiquitin-mediated proteolysis of CDKIs. Here, we modulated overall neddylation and SKP2-associated ubiquitination in HSCs by using SKP2-C25, an SKP2 inhibitor, and MLN4924 (Pevonedistat) as an inhibitor of the NEDD8 system. Treatments of SKP2-C25 and MLN4924 increased both murine and human stem and progenitor cell (HSPC) compartments. This is associated with the improved quiescence of murine HSC by upregulation of p27 and p57 CDKIs. A colony-forming unit assay showed an enhanced in vitro self-renewal potential post inhibition of ubiquitination and neddylation. In addition, MLN4924 triggered the mobilization of bone marrow HSPCs to peripheral blood. Intriguingly, MLN4924 treatment could decrease the proliferation of murine bone marrow mesenchymal stem cells or endothelial cells. These findings shed light on the contribution of SKP2, and associated ubiquitination and neddylation in HSC maintenance, self-renewal, and expansion.
    Keywords:  HSC; neddylation; small molecules; ubiquitination
  25. Cell Biosci. 2021 Jun 07. 11(1): 107
      BACKGROUND: Autophagy is required for oogenesis and plays a critical role in response to aging caused by oxidative stress. However, there have been no reports on regulation of cytoprotective autophagy in female germline stem cells (FGSCs) in response to aging caused by oxidative stress.RESULTS: We found that Spermidine (SPD) significantly increased protein expression of autophagy markers microtubule-associated protein 1 light chain 3 beta-II (MAP1LC3B-II/LC3B-II) and sequestosome-1/p62 (SQSTM1/p62), and evoked autophagic flux in FGSCs. Moreover, SPD increased the number and viability of FGSCs in vitro. Further, we found that SPD significantly reduced basal or hydrogen peroxide (H2O2)-induced up-regulated protein expression of the aging markers, cyclin dependent kinase inhibitor 2A (p16/CDKN2A) and tumor protein 53 (p53). After knockdown of p62 in FGSCs, p16 protein levels were significant higher compared with controls. However, protein p16 levels were not significantly changed in p62 knockdown FGSCs with SPD treatment compared with without SPD. Moreover, SPD significantly changed the expression of autophagy-related genes and pathways in FGSCs, as shown by bioinformatics analysis of RNA sequencing data. Additionally, SPD significantly inhibited AKT/mTOR phosphorylation.
    CONCLUSIONS: SPD induces cytoprotective autophagy in FGSCs in vitro and ameliorates cellular senescence of FGSCs induced by H2O2. Furthermore, SPD can ameliorate cellular senescence of FGSCs through p62. SPD might induce autophagy in FGSCs via the PI3K/Akt pathway. Our findings could be helpful for delaying aging of female germ cells due to oxidative stress and preserving female fertility.
    Keywords:  Anti- oxidative stress; Anti-aging; Autophagy; Female germline stem cells; Spermidine; p62
  26. Toxicol In Vitro. 2021 Jun 04. pii: S0887-2333(21)00123-5. [Epub ahead of print] 105198
      Paraquat (PQ) is a redox cycling herbicide known for its acute toxicity in humans. Airway parenchymal cells have been identified as primary sites for PQ accumulation, tissue inflammation and cellular injury. However, the role of immune cells in PQ induced tissue injury is largely unknown. To explore such mechanisms of PQ toxicity, primary human CD34+ stem cell derived macrophages (MCcd34) and dendritic cells (DCcd34) were established and characterised using RNA-Seq transcriptomic profiling. The impact of PQ on DCcd34 and MCcd34 cytotoxicity revealed increased sensitivity within DCcd34 cultures. PQ toxicity mechanisms were examined using sub-cytotoxic concentrations and TempO-seq transcriptomic assays. Comparable increases for several stress response pathway (NFE2L2, NF-kB and HSF) dependent genes were observed across both cell types. Interestingly, PQ induced unfolded protein response (UPR), p53, Irf and DC maturation genes in DCcd34, responses absent in MCcd34. Further exploration of the immune modifying potential of PQ was performed using the common allergen house dust mite (HD). Co-treatment of PQ and HD resulted in enhanced inflammatory responses within MCcd34 but not DCcd34. These results demonstrate for the first-time, immune cell type differential responses to PQ, that may underlie aspects of acute toxicity and susceptibility to inflammatory disease.
    Keywords:  Lung; Myeloid; TempO-Seq; Transcriptomics