bims-proarb 2021-09-19 papers

bims-proarb

Biomed News

on Proteostasis in aging and regenerative biology

Issue of 2021–09–19
23 papers selected by
Rich Giadone, Harvard University

Endoplasmic Reticulum Stress Induced Proliferation Remains Intact in Aging Mouse β-Cells.
Aging and Hypercholesterolemia Differentially Affect the Unfolded Protein Response in the Vasculature of ApoE-/- Mice.
BH3-only proteins are part of a regulatory network that control the sustained signalling of the unfolded protein response sensor IRE1α.
Caspase-12 and endoplasmic reticulum stress mediate neurotoxicity of pathological prion protein.
The intracellular milieu of Parkinson's disease patient brain cells modulates alpha-synuclein protein aggregation.
Increased fidelity of protein synthesis extends lifespan.
The Role of the UPR Pathway in the Pathophysiology and Treatment of Bipolar Disorder.
The Evolution of the Hallmarks of Aging.
Decreased Mitochondrial Membrane Potential Activates the Mitochondrial Unfolded Protein Response.
The AKT modulator A-443654 reduces α-synuclein expression and normalizes ER stress and autophagy.
The Regulatory Role of GBF1 on Osteoclast Activation Through EIF2a Mediated ER Stress and Novel Marker FAM129A Induction.
Heat Shock Protein 70 as a Sex-Skewed Regulator of α-Synucleinopathy.
Neurotoxicity of a pyrethroid pesticide deltamethrin is associated with the imbalance in proteolytic systems caused by mitophagy activation and proteasome inhibition.
p38 MAPK-mediated loss of nuclear RNase III enzyme Drosha underlies amyloid beta-induced neuronal stress in Alzheimer's disease.
Alpha-Synuclein defects autophagy by impairing SNAP29-mediated autophagosome-lysosome fusion.
Tacrine induces endoplasmic reticulum-stressed apoptosis via disrupting the proper assembly of oligomeric acetylcholinesterase in cultured neuronal cells.
Myocardial protein aggregates in pet guinea pigs.
Endoplasmic reticulum stress-mediated autophagy activation is involved in cadmium-induced ferroptosis of renal tubular epithelial cells.
Magnetite Fe3O4 Nanoparticles Enhance Mild Microwave Ablation of Tumor by Activating the IRE1-ASK1-JNK Pathway and Inducing Endoplasmic Reticulum Stress.
Dexmedetomidine alleviates traumatic spinal cord injury in rats via inhibiting apoptosis induced by endoplasmic reticulum stress.
A role for mitochondrial DNA in cellular proteostasis.
E3 Ubiquitin Ligase-Mediated Regulation of Osteoblast Differentiation and Bone Formation.
Oxidative stress-induced impairment of trophoblast function causes preeclampsia through the unfolded protein response pathway.

Front Endocrinol (Lausanne). 2021 ;12 734079

Endoplasmic Reticulum Stress Induced Proliferation Remains Intact in Aging Mouse β-Cells.

Jarin T Snyder, Christine Darko, Rohit B Sharma, Laura C Alonso.

  Aging is associated with loss of proliferation of the insulin-secreting β-cell, a possible contributing factor to the increased prevalence of type 2 diabetes in the elderly. Our group previously discovered that moderate endoplasmic reticulum (ER) stress occurring during glucose exposure increases the adaptive β-cell proliferation response. Specifically, the ATF6α arm of the tripartite Unfolded Protein Response (UPR) promotes β-cell replication in glucose excess conditions. We hypothesized that β-cells from older mice have reduced proliferation due to aberrant UPR signaling or an impaired proliferative response to ER stress or ATF6α activation. To investigate, young and old mouse islet cells were exposed to high glucose with low-dose thapsigargin or activation of overexpressed ATF6α, and β-cell proliferation was quantified by BrdU incorporation. UPR pathway activation was compared by qPCR of target genes and semi-quantitative Xbp1 splicing assay. Intriguingly, although old β-cells had reduced proliferation in high glucose compared to young β-cells, UPR activation and induction of proliferation in response to low-dose thapsigargin or ATF6α activation in high glucose were largely similar between young and old. These results suggest that loss of UPR-led adaptive proliferation does not explain the reduced cell cycle entry in old β-cells, and raise the exciting possibility that future therapies that engage adaptive UPR could increase β-cell number through proliferation even in older individuals.

Keywords:  ATF6 (activating transcription factor 6); aging/aging beta cells; endoplasm Reticulum Stress; pancreatic beta cells; proliferation; thapsigargin; unfolded protein response

DOI:  https://doi.org/10.3389/fendo.2021.734079
J Am Heart Assoc. 2021 Sep 17. e020441

Aging and Hypercholesterolemia Differentially Affect the Unfolded Protein Response in the Vasculature of ApoE-/- Mice.

Yuxiang Zhou, Xueping Wan, Kerstin Seidel, Mo Zhang, Jena B Goodman, Francesca Seta, Naomi Hamburg, Jingyan Han.

  Background Persistent activation of endoplasmic reticulum stress and the unfolded protein response (UPR) induces vascular cell apoptosis, contributing to atherogenesis. Aging and hypercholesterolemia are 2 independent proatherogenic factors. How they affect vascular UPR signaling remains unclear. Methods and Results Transcriptome analysis of aortic tissues from high fat diet-fed and aged ApoE-/- mice revealed 50 overlapping genes enriched for endoplasmic reticulum stress- and UPR-related pathways. Aortae from control, Western diet (WD)-fed, and aged ApoE-/- mice were assayed for (1) 3 branches of UPR signaling (pancreatic ER eIF2-alpha kinase /alpha subunit of the eukaryotic translation initiation factor 1/activating transcription factor 4, inositol-requiring enzyme 1 alpha/XBP1s, activating transcription factor 6); (2) UPR-mediated protective adaptation (upregulation of immunoglobulin heavy chain-binding protein and protein disulfide isomerase); and (3) UPR-mediated apoptosis (induction of C/EBP homologous transcription factor, p-JNK, and cleaved caspase-3). Aortic UPR signaling was differentially regulated in the aged and WD-fed groups. Consumption of WD activated all 3 UPR branches; in the aged aorta, only the ATF6α arm was activated, but it was 10 times higher than that in the WD group. BiP and protein disulfide isomerase protein levels were significantly decreased only in the aged aorta despite a 5-fold increase in their mRNA levels. Importantly, the aortae of aged mice exhibited a substantially enhanced proapoptotic UPR compared with that of WD-fed mice. In lung tissues, UPR activation and the resultant adaptive/apoptotic responses were not significantly different between the 2 groups. Conclusions Using a mouse model of atherosclerosis, this study provides the first in vivo evidence that aging and an atherogenic diet activate differential aortic UPR pathways, leading to distinct vascular responses. Compared with dietary intervention, aging is associated with impaired endoplasmic reticulum protein folding and increased aortic apoptosis.

Keywords:  aging; apoE deficient mice; hypercholesterolemia; unfolded protein response; vascular cells

DOI:  https://doi.org/10.1161/JAHA.120.020441
EMBO J. 2021 Sep 15. 40(18): e109146

BH3-only proteins are part of a regulatory network that control the sustained signalling of the unfolded protein response sensor IRE1α.

Diego A Rodriguez, Sebastian Zamorano, Fernanda Lisbona, Diego Rojas-Rivera, Hery Urra, Juan R Cubillos-Ruiz, Ricardo Armisen, Daniel R Henriquez, Emily H Cheng, Michal Letek, Tomas Vaisar, Thergiory Irrazabal, Christian Gonzalez-Billault, Anthony Letai, Felipe X Pimentel-Muiños, Guido Kroemer, Claudio Hetz.

DOI: https://doi.org/10.15252/embj.2021109146
EMBO J. 2021 Sep 15. 40(18): e109151

Caspase-12 and endoplasmic reticulum stress mediate neurotoxicity of pathological prion protein.

Claudio Hetz, Milene Russelakis-Carneiro, Kinsey Maundrell, Joaquin Castilla, Claudio Soto.

DOI: https://doi.org/10.15252/embj.2021109151
Acta Neuropathol Commun. 2021 Sep 16. 9(1): 153

The intracellular milieu of Parkinson's disease patient brain cells modulates alpha-synuclein protein aggregation.

Nadja Gustavsson, Ekaterina Savchenko, Oxana Klementieva, Laurent Roybon.

  Recent studies suggest that brain cell type specific intracellular environments may play important roles in the generation of structurally different protein aggregates that define neurodegenerative diseases. Using human induced pluripotent stem cells (hiPSC) and biochemical and vibrational spectroscopy techniques, we studied whether Parkinson's disease (PD) patient genomes could modulate alpha-synuclein (aSYN) protein aggregates formation. We found increased β-sheets and aggregated aSYN in PD patient hiPSC-derived midbrain cells, compared to controls. Importantly, we discovered that aSYN protein aggregation is modulated by patient brain cells' intracellular milieus at the primary nucleation phase. Additionally, we found changes in the formation of aSYN fibrils when employing cellular extracts from familial PD compared to idiopathic PD, in a Thioflavin T-based fluorescence assay. The data suggest that changes in cellular milieu induced by patient genomes trigger structural changes of aSYN potentially leading to the formation of strains having different structures, properties and seeding propensities.

Keywords:  Alpha-synuclein; Cellular environment; Human iPSCs; Midbrain spheroids; Parkinson’s disease; Protein aggregation

DOI:  https://doi.org/10.1186/s40478-021-01256-w
Cell Metab. 2021 Sep 08. pii: S1550-4131(21)00417-4. [Epub ahead of print]

Increased fidelity of protein synthesis extends lifespan.

Victoria Eugenia Martinez-Miguel, Celia Lujan, Tristan Espie-Caullet, Daniel Martinez-Martinez, Saul Moore, Cassandra Backes, Suam Gonzalez, Evgeniy R Galimov, André E X Brown, Mario Halic, Kazunori Tomita, Charalampos Rallis, Tobias von der Haar, Filipe Cabreiro, Ivana Bjedov.

  Loss of proteostasis is a fundamental process driving aging. Proteostasis is affected by the accuracy of translation, yet the physiological consequence of having fewer protein synthesis errors during multi-cellular organismal aging is poorly understood. Our phylogenetic analysis of RPS23, a key protein in the ribosomal decoding center, uncovered a lysine residue almost universally conserved across all domains of life, which is replaced by an arginine in a small number of hyperthermophilic archaea. When introduced into eukaryotic RPS23 homologs, this mutation leads to accurate translation, as well as heat shock resistance and longer life, in yeast, worms, and flies. Furthermore, we show that anti-aging drugs such as rapamycin, Torin1, and trametinib reduce translation errors, and that rapamycin extends further organismal longevity in RPS23 hyperaccuracy mutants. This implies a unified mode of action for diverse pharmacological anti-aging therapies. These findings pave the way for identifying novel translation accuracy interventions to improve aging.

Keywords:  RPS23; aging; archaea; mTOR; protein synthesis; proteostasis; ribosome; translation; translation accuracy; translation fidelity

DOI:  https://doi.org/10.1016/j.cmet.2021.08.017
Front Cell Neurosci. 2021 ;15 735622

The Role of the UPR Pathway in the Pathophysiology and Treatment of Bipolar Disorder.

Mahmoud Suliman, Michael W Schmidtke, Miriam L Greenberg.

  Bipolar disorder (BD) is a mood disorder that affects millions worldwide and is associated with severe mood swings between mania and depression. The mood stabilizers valproate (VPA) and lithium (Li) are among the main drugs that are used to treat BD patients. However, these drugs are not effective for all patients and cause serious side effects. Therefore, better drugs are needed to treat BD patients. The main barrier to developing new drugs is the lack of knowledge about the therapeutic mechanism of currently available drugs. Several hypotheses have been proposed for the mechanism of action of mood stabilizers. However, it is still not known how they act to alleviate both mania and depression. The pathology of BD is characterized by mitochondrial dysfunction, oxidative stress, and abnormalities in calcium signaling. A deficiency in the unfolded protein response (UPR) pathway may be a shared mechanism that leads to these cellular dysfunctions. This is supported by reported abnormalities in the UPR pathway in lymphoblasts from BD patients. Additionally, studies have demonstrated that mood stabilizers alter the expression of several UPR target genes in mouse and human neuronal cells. In this review, we outline a new perspective wherein mood stabilizers exert their therapeutic mechanism by activating the UPR. Furthermore, we discuss UPR abnormalities in BD patients and suggest future research directions to resolve discrepancies in the literature.

Keywords:  bipolar disorder; endoplasmic reticulum stress; lithium; mood disorder; unfolded protein response; valproate

DOI:  https://doi.org/10.3389/fncel.2021.735622
Front Genet. 2021 ;12 693071

The Evolution of the Hallmarks of Aging.

Maël Lemoine.

  The evolutionary theory of aging has set the foundations for a comprehensive understanding of aging. The biology of aging has listed and described the "hallmarks of aging," i.e., cellular and molecular mechanisms involved in human aging. The present paper is the first to infer the order of appearance of the hallmarks of bilaterian and thereby human aging throughout evolution from their presence in progressively narrower clades. Its first result is that all organisms, even non-senescent, have to deal with at least one mechanism of aging - the progressive accumulation of misfolded or unstable proteins. Due to their cumulation, these mechanisms are called "layers of aging." A difference should be made between the first four layers of unicellular aging, present in some unicellular organisms and in all multicellular opisthokonts, that stem and strike "from the inside" of individual cells and span from increasingly abnormal protein folding to deregulated nutrient sensing, and the last four layers of metacellular aging, progressively appearing in metazoans, that strike the cells of a multicellular organism "from the outside," i.e., because of other cells, and span from transcriptional alterations to the disruption of intercellular communication. The evolution of metazoans and eumetazoans probably solved the problem of aging along with the problem of unicellular aging. However, metacellular aging originates in the mechanisms by which the effects of unicellular aging are kept under control - e.g., the exhaustion of stem cells that contribute to replace damaged somatic cells. In bilaterians, additional functions have taken a toll on generally useless potentially limited lifespan to increase the fitness of organisms at the price of a progressively less efficient containment of the damage of unicellular aging. In the end, this picture suggests that geroscience should be more efficient in targeting conditions of metacellular aging rather than unicellular aging itself.

Keywords:  aging; bilaterians; evolution; geroscience; metacellular aging; unicellular aging

DOI:  https://doi.org/10.3389/fgene.2021.693071
MicroPubl Biol. 2021 ;2021

Decreased Mitochondrial Membrane Potential Activates the Mitochondrial Unfolded Protein Response.

Brandon J Berry, Tyrone O Nieves, Andrew P Wojtovich.

Mitochondria are ATP-producing organelles that also signal throughout the cell. Mitochondrial protein homeostasis is regulated through membrane potential-dependent protein import and quality control signaling. The mitochondrial unfolded protein response (UPRmt) is a specific program that responds to imbalances in nuclear and mitochondrial gene expression. Mounting evidence suggests that the electrochemical gradient that powers mitochondrial function, the mitochondrial membrane potential (Δψm), is a core regulator of the UPRmt. Here we tested this notion directly by pharmacologically dissipating Δψm and monitoring UPRmt activation. We found that chemical dissipation of Δψm using FCCP indeed activated UPRmt dose-dependently in C. elegans assayed by the HSP-60::GFP reporter strain.

DOI: https://doi.org/10.17912/micropub.biology.000445
J Biol Chem. 2021 Sep 11. pii: S0021-9258(21)00993-5. [Epub ahead of print] 101191

The AKT modulator A-443654 reduces α-synuclein expression and normalizes ER stress and autophagy.

Mandi Gandelman, Warunee Dansithong, Stephen C Kales, Sharan Paul, Gentrie Maag, Erika Aoyama, Alexey Zakharov, Ganesha Rai, Thomas Dexheimer, Brooke M Whitehill, Hongmao Sun, Ajit Jadhav, Anton Simeonov, Mark J Henderson, Duong P Huynh, Stefan M Pulst, Daniel R Scoles.

  Accumulation of α-synuclein is a main underlying pathological feature of Parkinson's disease (PD) and α-synucleinopathies, for which lowering expression of the α-synuclein gene (SNCA) is a potential therapeutic avenue. Using a cell-based luciferase reporter of SNCA expression we performed a quantitative high throughput screen (qHTS) of 155,885 compounds and identified A-443654, an inhibitor of the multiple functional kinase AKT, as a potent inhibitor of SNCA. HEK-293 cells with CAG repeat expanded ATXN2 (ATXN2-Q58 cells) have increased levels of α-synuclein. We found that A-443654 normalized levels of both SNCA mRNA and α-synuclein monomers and oligomers in ATXN2-Q58 cells. A-443654 also normalized levels of α-synuclein in fibroblasts and iPSC-derived dopaminergic neurons from a patient carrying a triplication of the SNCA gene. Analysis of autophagy and endoplasmic reticulum stress markers showed that A-443654 successfully prevented α-synuclein toxicity and restored cell function in ATXN2-Q58 cells, normalizing the levels of mTOR, LC3-II, p62, STAU1, BiP and CHOP. A-443654 also decreased the expression of DCLK1, an inhibitor of α-synuclein lysosomal degradation. Our study identifies A-443654 and AKT inhibition as a potential strategy for reducing SNCA expression and preventing PD pathology.

Keywords:  A-443654; AKT; Parkinson disease; SNCA; STAU1; alpha‐synuclein (α‐synuclein); autophagy; endoplasmic reticulum stress (ER stress); high‐throughput screening (HTS); staufen1

DOI:  https://doi.org/10.1016/j.jbc.2021.101191
Front Cell Dev Biol. 2021 ;9 706768

The Regulatory Role of GBF1 on Osteoclast Activation Through EIF2a Mediated ER Stress and Novel Marker FAM129A Induction.

Cailing Wen, Yuheng Zhou, Yanting Xu, Huijing Tan, Caixia Pang, Haiqian Liu, Kaifei Liu, Linlin Wei, Hui Luo, Tian Qin, Chonghua He, Cuiling Liu, Chun Zhou.

  Bone-resorbing activities of osteoclasts (OCs) are highly dependent on actin cytoskeleton remodeling, plasma membrane reorganization, and vesicle trafficking pathways, which are partially regulated by ARF-GTPases. In the present study, the functional roles of Golgi brefeldin A resistance factor 1 (GBF1) are proposed. GBF1 is responsible for the activation of the ARFs family and vesicular transport at the endoplasmic reticulum-Golgi interface in different stages of OCs differentiation. In the early stage, GBF1 deficiency impaired OCs differentiation and was accompanied with OCs swelling and reduced formation of mature OCs, indicating that GBF1 participates in osteoclastogenesis. Using siRNA and the specific inhibitor GCA for GBF1 knockdown upregulated endoplasmic reticulum stress-associated signaling molecules, including BiP, p-PERK, p-EIF2α, and FAM129A, and promoted autophagic Beclin1, Atg7, p62, and LC3 axis, leading to apoptosis of OCs. The present data suggest that, by blocking COPI-mediated vesicular trafficking, GBF1 inhibition caused intense stress to the endoplasmic reticulum and excessive autophagy, eventually resulting in the apoptosis of mature OCs and impaired bone resorption function.

Keywords:  GBF1; autophagy; bone; endoplasmic reticulum stress; osteoclast

DOI:  https://doi.org/10.3389/fcell.2021.706768
Neurotherapeutics. 2021 Sep 15.

Heat Shock Protein 70 as a Sex-Skewed Regulator of α-Synucleinopathy.

Tarun N Bhatia, Rachel N Clark, Patrick G Needham, Kristin M Miner, Anuj S Jamenis, Elizabeth A Eckhoff, Nevil Abraham, Xiaoming Hu, Peter Wipf, Kelvin C Luk, Jeffrey L Brodsky, Rehana K Leak.

  The role of molecular chaperones, such as heat shock protein 70 (Hsp70), is not typically studied as a function of biological sex, but by addressing this gap we might improve our understanding of proteinopathic disorders that predominate in one sex. Therefore, we exposed male or female primary hippocampal cultures to preformed α-synuclein fibrils in a model of early-stage Lewy pathology. We first discovered that two mechanistically distinct inhibitors of Hsp70 function increased phospho-α-synuclein+ inclusions more robustly in male-derived neurons. Because Hsp70 is released into extracellular compartments and may restrict cell-to-cell transmission/amplification of α-synucleinopathy, we then tested the effects of low-endotoxin, exogenous Hsp70 (eHsp70) in primary hippocampal cultures. eHsp70 was taken up by and reduced α-synuclein+ inclusions in cells of both sexes, but pharmacological suppression of Hsp70 function attenuated the inhibitory effect of eHsp70 on perinuclear inclusions only in male neurons. In 20-month-old male mice infused with α-synuclein fibrils in the olfactory bulb, daily intranasal eHsp70 delivery also reduced inclusion numbers and the time to locate buried food. eHsp70 penetrated the limbic system and spinal cord of male mice within 3 h but was cleared within 72 h. Unexpectedly, no evidence of eHsp70 uptake from nose into brain was observed in females. A trend towards higher expression of inducible Hsp70-but not constitutive Hsp70 or Hsp40-was observed in amygdala tissues from male subjects with Lewy body disorders compared to unaffected male controls, supporting the importance of this chaperone in human disease. Women expressed higher amygdalar Hsp70 levels compared to men, regardless of disease status. Together, these data provide a new link between biological sex and a key chaperone that orchestrates proteostasis.

Keywords:  Chaperone; Dementia with Lewy bodies; Intranasal; Parkinson’s disease; Proteostasis; Synuclein

DOI:  https://doi.org/10.1007/s13311-021-01114-6
Toxicol Appl Pharmacol. 2021 Sep 11. pii: S0041-008X(21)00327-6. [Epub ahead of print] 115723

Neurotoxicity of a pyrethroid pesticide deltamethrin is associated with the imbalance in proteolytic systems caused by mitophagy activation and proteasome inhibition.

Tetsushi Hirano, Nihei Suzuki, Yoshinori Ikenaka, Nobuhiko Hoshi, Yoshiaki Tabuchi.

  Pyrethroids are one of the most commonly used classes of synthetic pesticides in the world. Recent laboratory and epidemiological evidence suggested that pyrethroids have potential adverse effects in the mammalian brain; however, the underlying mechanisms of the neurotoxic effects of pyrethroids have not been fully elucidated. In the present study, we investigated the mechanisms of effects of a type II pyrethroid deltamethrin (DM) in a neuronal cell model focusing on the proteolytic function, including autophagy and the ubiquitin-proteasome system. We confirmed that a micromolar concentration of DM dose-dependently decreased the cell viability and induced apoptotic cell death. Our results showed that DM enhanced autophagy in association with an accumulation of autophagosomes and increase in the levels of autophagy markers LC3-II/LC3-I ratio and p62 which were much elevated in the presence of lysosomal inhibitors bafilomycin A1 and chloroquine. We also found that DM caused a dysfunction of mitochondria with a decrease of mitochondrial membrane potential and mitochondrial DNA copy number as well as colocalization with autophagosomes. Moreover, a decrease in the activities of three major proteasomal enzymes and an accumulation of ubiquitinated proteins were observed by the exposure to DM. Transcriptome analysis revealed that up-regulated genes supported the activation of autophagy with induction of cellular stress responses including oxidative stress and endoplasmic reticulum stress, while down-regulated genes related to the cell cycle and DNA replication. These findings provide novel insights into the neurotoxicity of DM which underlie the imbalance in proteolytic function caused by mitophagy activation and proteasome inhibition.

Keywords:  Autophagy; Deltamethrin; Mitochondrial dysfunction; Neurotoxicity; Pyrethroid; Ubiquitin-proteasome system

DOI:  https://doi.org/10.1016/j.taap.2021.115723
Aging Cell. 2021 Sep 16. e13434

p38 MAPK-mediated loss of nuclear RNase III enzyme Drosha underlies amyloid beta-induced neuronal stress in Alzheimer's disease.

Haidong Xu, Xiaolei Liu, Wenming Li, Ye Xi, Peng Su, Bo Meng, Xiaoyun Shao, Beisha Tang, Qian Yang, Zixu Mao.

  MicroRNAs (miRNAs) are small noncoding RNAs ubiquitously expressed in the brain and regulate gene expression at the post-transcriptional level. The nuclear RNase III enzyme Drosha initiates the maturation process of miRNAs in the nucleus. Strong evidence suggests that dysregulation of miRNAs is involved in many neurological disorders including Alzheimer's disease (AD). Dysfunction of miRNA biogenesis components may be involved in the processes of those diseases. However, the role of Drosha in AD remains unknown. By using immunohistochemistry, biochemistry, and subcellular fractionation methods, we show here that the level of Drosha protein was significantly lower in the postmortem brain of human AD patients as well as in the transgenic rat model of AD. Interestingly, Drosha level was specifically reduced in neurons of the cortex and hippocampus but not in the cerebellum in the AD brain samples. In primary cortical neurons, amyloid-beta (Aβ) oligomers caused a p38 MAPK-dependent phosphorylation of Drosha, leading to its redistribution from the nucleus to the cytoplasm and a decrease in its level. This loss of Drosha function preceded Aβ-induced neuronal death. Importantly, inhibition of p38 MAPK activity or overexpression of Drosha protected neurons from Aβ oligomers-induced apoptosis. Taken together, these results establish a role for p38 MAPK-Drosha pathway in modulating neuronal viability under Aβ oligomers stress condition and implicate loss of Drosha as a key molecular change in the pathogenesis of AD.

Keywords:  Alzheimer's disease; Drosha; amyloid beta (Aβ); neuronal death; p38 MAPK

DOI:  https://doi.org/10.1111/acel.13434
Cell Death Dis. 2021 Sep 17. 12(10): 854

Alpha-Synuclein defects autophagy by impairing SNAP29-mediated autophagosome-lysosome fusion.

Qilin Tang, Pan Gao, Thomas Arzberger, Matthias Höllerhage, Jochen Herms, Günter Höglinger, Thomas Koeglsperger.

Dopaminergic (DA) cell death in Parkinson's disease (PD) is associated with the gradual appearance of neuronal protein aggregates termed Lewy bodies (LBs) that are comprised of vesicular membrane structures and dysmorphic organelles in conjunction with the protein alpha-Synuclein (α-Syn). Although the exact mechanism of neuronal aggregate formation and death remains elusive, recent research suggests α-Syn-mediated alterations in the lysosomal degradation of aggregated proteins and organelles - a process termed autophagy. Here, we used a combination of molecular biology and immunochemistry to investigate the effect of α-Syn on autophagy turnover in cultured human DA neurons and in human post-mortem brain tissue. We found α-Syn overexpression to reduce autophagy turnover by compromising the fusion of autophagosomes with lysosomes, thus leading to a decrease in the formation of autolysosomes. In accord with a compensatory increase in the plasma membrane fusion of autophagosomes, α-Syn enhanced the number of extracellular vesicles (EV) and the abundance of autophagy-associated proteins in these EVs. Mechanistically, α-Syn decreased the abundance of the v-SNARE protein SNAP29, a member of the SNARE complex mediating autophagolysosome fusion. In line, SNAP29 knockdown mimicked the effect of α-Syn on autophagy whereas SNAP29 co-expression reversed the α-Syn-induced changes on autophagy turnover and EV release and ameliorated DA neuronal cell death. In accord with our results from cultured neurons, we found a stage-dependent reduction of SNAP29 in SNc DA neurons from human post-mortem brain tissue of Lewy body pathology (LBP) cases. In summary, our results thus demonstrate a previously unknown effect of α-Syn on intracellular autophagy-associated SNARE proteins and, as a consequence, a reduced autolysosome fusion. As such, our findings will therefore support the investigation of autophagy-associated pathological changes in PD.

DOI: https://doi.org/10.1038/s41419-021-04138-0
Mol Pharmacol. 2021 Sep 16. pii: MOLPHARM-AR-2021-000269. [Epub ahead of print]

Tacrine induces endoplasmic reticulum-stressed apoptosis via disrupting the proper assembly of oligomeric acetylcholinesterase in cultured neuronal cells.

Etta Y L Liu, Shinghung Mak, Xiangpeng Kong, Yingjie Xia, Kenneth K L Kwan, Miranda L Xu, Karl W K Tsim.

  Acetylcholinesterase inhibitors (AChEIs), the most developed treatment strategies for Alzheimer's disease (AD), will be used in clinic for, at least, the next decades. Their side effects are in highly variable from drug to drug whose mechanism remain to be fully established. The withdrawal of tacrine (Cognex®) in the market makes it as an interesting case study. Here, we found tacrine could disrupt the proper trafficking of proline-rich membrane anchor-linked tetrameric AChE in the endoplasmic reticulum (ER). The exposure of tacrine in cells expressing AChE, e.g. neuron, caused an accumulation of the misfolded AChE in the ER. This misfolded enzyme was not able to transport to Golgi/plasma membrane, which subsequently induced ER stress and its downstream signaling cascade of unfolded protein response (UPR). Once the stress was overwhelming, the cooperation of ER with mitochondria increased the loss of mitochondrial membrane potential. Eventually, the tacrine-exposed cells lost homeostasis and undergone apoptosis. The ER stress and apoptosis, induced by tacrine, were proportional to the amount of AChE. Other AChEIs (rivastigmine, bis(3)-cognitin, daurisoline and dauricine) could cause the same problem as tacrine by inducing ER stress in neuronal cells. The results provide guidance for the drug design and discovery of AChEIs for AD treatment. Significance Statement AChEIs are the most developed treatment strategies for Alzheimer's disease (AD) and will be used in clinic for at least the next decades. Our study reports tacrine and other AChEIs disrupt the proper trafficking of AChE in the endoplasmic reticulum. Eventually, the apoptosis of neurons and other cells are induced. The results provide guidance for drug design and discovery of AChEIs for AD treatment.

Keywords:  Alzheimer's Disease; Apoptosis; acetylcholinesterase

DOI:  https://doi.org/10.1124/molpharm.121.000269
Vet Pathol. 2021 Sep 16. 3009858211042586

Myocardial protein aggregates in pet guinea pigs.

Teresa Southard, Kathleen Kelly, Anibal G Armien.

  A retrospective study of guinea pigs submitted for necropsy revealed intracytoplasmic inclusions in the cardiomyocytes of 26 of 30 animals. The inclusions were found with approximately the same frequency in male and female guinea pigs and were slightly more common in older animals. In most cases, the animals did not have clinical signs or necropsy findings suggestive of heart failure, and the cause of death or reason for euthanasia was attributed to concurrent disease processes. However, the 4 guinea pigs with the highest inclusion body burden all had pulmonary edema, sometimes with intra-alveolar hemosiderin-laden macrophages, suggestive of heart failure. The inclusions were found in both the left and right ventricular myocardium, mainly in the papillary muscles, but were most common in the right ventricular free wall. No inclusions were detected in the atrial myocardium or in skeletal muscle. The inclusions did not stain with Congo red or periodic acid-Schiff. Electron microscopy revealed dense aggregates of disorganized myofilaments and microtubules that displaced and compressed the adjacent organelles. By immunohistochemistry, there was some scattered immunoreactivity for desmin and actin at the periphery of the inclusions and punctate actin reactivity within the aggregates. The inclusions did not react with antibodies to ubiquitin or cardiac myosin, but were variably reactive for alpha B crystallin, a small heat shock chaperone protein. The inclusions were interpreted as evidence of impaired proteostasis.

Keywords:  alpha B crystallin; cardiovascular; chinchilla; guinea pig; heart; myofibrillary myopathy; porcupine; protein aggregate myopathy; proteostasis

DOI:  https://doi.org/10.1177/03009858211042586
Free Radic Biol Med. 2021 Sep 11. pii: S0891-5849(21)00721-8. [Epub ahead of print]175 236-248

Endoplasmic reticulum stress-mediated autophagy activation is involved in cadmium-induced ferroptosis of renal tubular epithelial cells.

Caijun Zhao, Duo Yu, Zhaoqi He, Lijuan Bao, Lianjun Feng, Luotong Chen, Zhuoyu Liu, Xiaoyu Hu, Naisheng Zhang, Tiejun Wang, Yunhe Fu.

  Acute cadmium (Cd) exposure is a significant risk factor for renal injury and lacks effective treatment strategies. Ferroptosis is a recently identified iron-dependent form of nonapoptotic cell death mediated by membrane damage resulting from lipid peroxidation, and it is implicated in many diseases. However, whether ferroptosis is involved in Cd-induced renal injury and, if so, how it operates. Here, we show that Cd can induce ferroptosis in kidney and renal tubular epithelial cells, as demonstrated by elevation of intracellular iron levels and lipid peroxidation, as well as impaired antioxidant production. Treatment with a ferroptosis inhibitor alleviated Cd-induced cell death. Intriguingly, we established that Cd-induced ferroptosis depended on endoplasmic reticulum (ER) stress, by demonstrating that Cd activated the PERK-eIF2α-ATF4-CHOP pathway and that inhibition of ER stress reduced ferroptosis caused by Cd. We further found that autophagy was required for Cd-induced ferroptosis because the inhibition of autophagy by chloroquine mitigated Cd-induced ferroptosis. Furthermore, we showed that iron dysregulation by ferritinophagy contributed to Cd-induced ferroptosis, by showing that the iron chelator desferrioxamine alleviated Cd-induced cell death and lipid peroxidation. In addition, ER stress is likely activated by MitoROS which trigger autophagy and ferroptosis. Collectively, our results indicate that ferroptosis is involved in Cd-induced renal toxicity and regulated by the MitoROS-ER stress-ferritinophagy axis.

Keywords:  Autophagy; Cd; ER stress; Ferroptosis; Renal tubular

DOI:  https://doi.org/10.1016/j.freeradbiomed.2021.09.008
Int J Nanomedicine. 2021 ;16 6129-6140

Magnetite Fe3O4 Nanoparticles Enhance Mild Microwave Ablation of Tumor by Activating the IRE1-ASK1-JNK Pathway and Inducing Endoplasmic Reticulum Stress.

Shuai Li, Yi Liu, Xinyi Liu, Bin Lan, Wanwan Li, Fang Guo.

   Purpose: With the development of nanomedicine, microwave ablation enhanced by multifunctional nanoplatforms has been widely studied for synergistic cancer therapy. Though scientists have got a lot of significant achievements in this field, the detailed molecular mechanisms and potential targets of microwave ablation enhanced by multifunctional nanoplatforms still need further exploration. In this study, we found that a kind of magnetite Fe3O4 nanoparticles (Fe3O4 NPs) could induce severe endoplasmic reticulum stress and activate cancer apoptosis under the irradiation of mild microwave.
Methods: In this study, plenty of studies including cell immunofluorescence, mitochondrial membrane potential, electron microscopy, atomic force microscopy and microwave ablation in vivo were conducted to explore the molecular mechanisms and potential targets of microwave ablation enhanced by the Fe3O4 NPs.
Results: The IRE1-ASK1-JNK pathway was strongly activated in A375 cells treated with both Fe3O4 NPs and mild microwave. The endoplasmic reticulum of the A375 cells was significantly dilated and exhibited ballooning degeneration. By investigating the mitochondrial membrane potential (ΔΨm), we found that the mitochondria of cancer cells had been significantly damaged under microwave treatment coupled with Fe3O4 NPs. In addition, melanoma of B16F10-bearing mice had also been effectively inhibited after being treated with Fe3O4 NPs and microwave.
Conclusion: In this study, we found that a kind of magnetite Fe3O4 nanoparticles could induce severe ER stress and activate cancer apoptosis under mild microwave irradiation. Apparent apoptosis had been observed in the A375 cells under a scanning electron microscope and transmission electron microscope. Moreover, melanoma had also been inhibited effectively in vivo. As a result, the endoplasmic reticulum stress is a promising target with clinical potential in nanomedicine and cancer therapy.

Keywords:  ER stress; apoptosis; magnetite Fe3O4 nanoparticles; microwave ablation

DOI:  https://doi.org/10.2147/IJN.S312823
Neurol Res. 2021 Sep 17. 1-10

Dexmedetomidine alleviates traumatic spinal cord injury in rats via inhibiting apoptosis induced by endoplasmic reticulum stress.

Yi-Bin Liu, Wei-Feng Liu, Wei-Can Chen, Wei Li, Yan-Ling Lin, Chong-Jun Xu, He-Fan He.

   OBJECTIVE: To investigate the protective effect of dexmedetomidine (Dex) on traumatic spinal cord injury (TSCI) and to evaluate the involvement of inhibition of endoplasmic reticulum (ER) stress response in the potential mechanism.
METHOD: Sprague-Dawley rats were randomly divided into five groups. The hind limb locomotor function of rats was evaluated at 1, 3 and 7 days after the operation. At 7 days after the operation, spinal cord specimens were obtained for hematoxylin and eosin (H&E), Nissl and TUNEL staining, as well as immunofluorescence and Western blot analyses to detect the level of apoptosis and the levels of proteins related to ER stress.
RESULTS: 7 days after the operation, Dex treatment promoted the recovery and also inhibited apoptosis of neurons in the spinal cord. Additionally, Dexinhibited the expression of proteins related to ER stress response after spinal cord injury.
CONCLUSIONS: Dex improves the neurological function of rats with TSCI and reduces apoptosis of spinal cord neurons. The potential mechanism is related to the inhibition of the ER stress response.

Keywords:  Dexmedetomidine; apoptosis; endoplasmic reticulum stress; neuroprotection; traumatic spinal cord injury

DOI:  https://doi.org/10.1080/01616412.2021.1979750
Nat Rev Genet. 2021 Sep 13.

A role for mitochondrial DNA in cellular proteostasis.

Caroline Barranco.

DOI: https://doi.org/10.1038/s41576-021-00418-9
Front Cell Dev Biol. 2021 ;9 706395

E3 Ubiquitin Ligase-Mediated Regulation of Osteoblast Differentiation and Bone Formation.

Jianlin Shen, Bowen Fu, Yanfang Li, Yanjiao Wu, Hongxun Sang, Heshi Zhang, Haibin Lin, Huan Liu, Wenhua Huang.

  The ubiquitin-proteasome system (UPS) is an essential pathway that regulates the homeostasis and function of intracellular proteins and is a crucial protein-degradation system in osteoblast differentiation and bone formation. Abnormal regulation of ubiquitination leads to osteoblast differentiation disorders, interfering with bone formation and ultimately leading to osteoporosis. E3 ubiquitin ligases (E3) promote addition of a ubiquitin moiety to substrate proteins, specifically recognizing the substrate and modulating tyrosine kinase receptors, signaling proteins, and transcription factors involved in the regulation of osteoblast proliferation, differentiation, survival, and bone formation. In this review, we summarize current progress in the understanding of the function and regulatory effects of E3 ligases on the transcription factors and signaling pathways that regulate osteoblast differentiation and bone formation. A deep understanding of E3 ligase-mediated regulation of osteoblast differentiation provides a scientific rationale for the discovery and development of novel E3-targeting therapeutic strategies for osteoporosis.

Keywords:  E3 ubiquitin ligase; bone formation; osteoblast differentiation; signaling pathway; therapeutic target; transcription factor

DOI:  https://doi.org/10.3389/fcell.2021.706395
Sci Rep. 2021 Sep 16. 11(1): 18415

Oxidative stress-induced impairment of trophoblast function causes preeclampsia through the unfolded protein response pathway.

Indrani Mukherjee, Ruby Dhar, Sunil Singh, Jai Bhagwan Sharma, Tapas Chandra Nag, Asit Ranjan Mridha, Parul Jaiswal, Subhrajit Biswas, Subhradip Karmakar.

Pre-eclampsia (PE) is a pregnancy-specific disorder, characterized by hypertension and proteinuria. In PE, trophoblasts mediated inadequate remodeling of uterine spiral arteries seem to interrupt uteroplacental blood flow, one of the hallmarks in the early onset of PE (EO-PE). This, in turn, results in placental ischemia-reperfusion injury during hypoxia and reoxygenation episodes, leading to the generation of reactive oxygen species (ROS) and oxidative stress (OS). But still it is debatable if OS is a cause or consequence of PE. In this present study, we have investigated the effects of OS on PE placentae and trophoblast cell functions using BeWo and HTR8/SVneo cell lines. PE placental tissues showed abnormal ultrastructure, high level of reactive oxygen species (ROS) with altered unfolded protein responses (UPR) in compare with term placental tissues. Similar to PE placentae, during OS induction, the trophoblast cells showed altered invasion and migration properties with significantly variable expression of differentiation and invasion markers, e.g., syncytin and MMPs. The effect was rescued by antioxidant, N-acetyl cysteine, thereby implying a ROS-specific effect and in the trophoblast cells, OS triggers UPR pathway through IRE1α-XBP1 axis. Taken together, these findings highlight the harmful effect of unfolded protein response, which was induced due to OS on trophoblast cells and deformed invasion and differentiation programme and can be extended further to clinical settings to identify clinically approved antioxidants during pregnancy as a therapeutic measure to reduce the onset of PE.

DOI: https://doi.org/10.1038/s41598-021-97799-y