Cellular Protein Quality Control Research Articles

Comprehensive perspective towards the management of proteinopathies by elucidating protein misfolding and aggregation.

Protein misfolding and aggregation is the phenomenon of the generic propensity of proteins, considered as a dark side of the protein world, and its exact mechanism is still not deciphered. Understanding the complexity of protein aggregation is currently the primary apprehension and challenge in biology and medicine due to their association with various debilitating human proteinopathies and neurodegenerative diseases. The mechanism of protein aggregation, associated diseases, and the development of efficient therapeutic strategies against these diseases are very challenging. These diseases are caused by different proteins, each protein with different mechanisms and consisting of various microscopic phases or events. These microscopic steps are functioning on different timescales during aggregation. Here, we highlighted the different features and current trends in protein aggregation. The study thoroughly recapitulates the various factors influencing, possible causes, types of aggregates and aggregation, their different proposed mechanisms, and the methods used to study the aggregation. Additionally, the formation and elimination of misfolded or aggregated proteins in the cell, the role of the ruggedness of the protein folding landscape in protein aggregation, proteinopathies, and the challenges for their prevention are comprehensively elucidated. A holistic understanding of different aspects of aggregation, molecular steps governing the various features of protein quality control, and crucial queries about the modulation of these processes and their interactions with other systems in cellular protein quality control can be considered conducive to comprehending the mechanism, designing effective approaches towards prevention of protein aggregation, rationalizing the etiology and development of novel strategies against therapy and management of the proteinopathies.

Potential Role of Endoplasmic Reticulum Stress in Modulating Protein Homeostasis in Oligodendrocytes to Improve White Matter Injury in Preterm Infants.

Preterm white matter injury (WMI) is a demyelinating disease with high incidence and mortality in premature infants. Oligodendrocyte cells (OLs) are a specialized glial cell that produces myelin proteins and adheres to the axons providing energy and metabolic support which susceptible to endoplasmic reticulum protein quality control. Disruption of cellular protein homeostasis led to OLs dysfunction and cell death, immediately, the unfolded protein response (UPR) activated to attempt to restore the protein homeostasis via IRE1/XBP1s, PERK/eIF2α and ATF6 pathway that reduced protein translation, strengthen protein-folding capacity, and degraded unfolding/misfolded protein. Moreover, recent works have revealed the conspicuousness function of ER signaling pathways in regulating influenced factors such as calcium homeostasis, mitochondrial reactive oxygen generation, and autophagy activation to regulate protein hemostasis and improve the myelination function of OLs. Each of the regulation modes and their corresponding molecular mechanisms provides unique opportunities and distinct perspectives to obtain a deep understanding of different actions of ER stress in maintaining OLs' health and function. Therefore, our review focuses on summarizing the current understanding of ER stress on OLs' protein homeostasis micro-environment in myelination during white matter development, as well as the pathophysiology of WMI, and discussing the further potential experimental therapeutics targeting these factors that restore the function of the UPR in OLs myelination function. Potential Role of ER Stress in Modulating Protein Homeostasis in OLs. OLs, produce myelin proteins and provide energy and metabolic support which are susceptible to cellular protein homeostasis and ER protein quality control. 1) UPR plays a different role in activating IRE1/XBP1s, PERK/eIF2α, and ATF6 pathways not only in attempting to restore protein homeostasis to promote cell survival but also aggravating disruption of cellular protein homeostasis to accelerate cell death. 2) PERK pathway facilitated the protein secretion, amino acid metabolism, and stress response to promote cell survival via phosphorylating eIF2α level and strengthening ATF4 expression; Nevertheless, the prolonged activating of the PERK pathway could up-regulate CHOP, GADD34, and other pro-apoptotic factors to further aggravates cell injury. 3) IRE1 and ATF6 pathways enhanced various gene transcription associated with protein folding, secreting, EARD, and ERQC to prompt cell protein homeostasis micro-environment; However, sustained IRE1 and/or ATF6 activity could prompt cell survival toward apoptosis via the pro-apoptotic pathway, inflammation, and other patterns.

Aggrephagy-related gene signature correlates with survival and tumor-associated macrophages in glioma: Insights from single-cell and bulk RNA sequencing.

Aggrephagy is a lysosome-dependent process that degrades misfolded protein condensates to maintain cancer cell homeostasis. Despite its importance in cellular protein quality control, the role of aggrephagy in glioma remains poorly understood. To investigate the expression of aggrephagy-related genes (ARGs) in glioma and in different cell types of gliomas and to develop an ARGs-based prognostic signature to predict the prognosis, tumor microenvironment, and immunotherapy response of gliomas. ARGs were identified by searching the Reactome database. We developed the ARGs-based prognostic signature (ARPS) using data from the Cancer Genome Atlas (TCGA, n = 669) by Lasso-Cox regression. We validated the robustness of the signature in clinical subgroups and CGGA cohorts (n = 970). Gene set enrichment analysis (GSEA) was used to identify the pathways enriched in ARPS subgroups. The correlations between ARGs and macrophages were also investigated at single cell level. A total of 44 ARGs showed heterogeneous expression among different cell types of gliomas. Five ARGs (HSF1, DYNC1H1, DYNLL2, TUBB6, TUBA1C) were identified to develop ARPS, an independent prognostic factor. GSEA showed gene sets of patients with high-ARPS were mostly enriched in cell cycle, DNA replication, and immune-related pathways. High-ARPS subgroup had higher immune cell infiltration states, particularly macrophages, Treg cells, and neutrophils. APRS had positive association with tumor mutation burden (TMB) and immunotherapy response predictors. At the single cell level, we found ARGs correlated with macrophage development and identified ARGs-mediated macrophage subtypes with distinct communication characteristics with tumor cells. VIM+ macrophages were identified as pro-inflammatory and had higher interactions with malignant cells. We identified a novel signature based on ARGs for predicting glioma prognosis, tumor microenvironment, and immunotherapy response. We highlight the ARGs-mediated macrophages in glioma exhibit classical features.

Paralogue-Specific Roles of SUMO1 and SUMO2/3 in Protein Quality Control and Associated Diseases.

Small ubiquitin-related modifiers (SUMOs) function as post-translational protein modifications and regulate nearly every aspect of cellular function. While a single ubiquitin protein is expressed across eukaryotic organisms, multiple SUMO paralogues with distinct biomolecular properties have been identified in plants and vertebrates. Five SUMO paralogues have been characterized in humans, with SUMO1, SUMO2 and SUMO3 being the best studied. SUMO2 and SUMO3 share 97% protein sequence homology (and are thus referred to as SUMO2/3) but only 47% homology with SUMO1. To date, thousands of putative sumoylation substrates have been identified thanks to advanced proteomic techniques, but the identification of SUMO1- and SUMO2/3-specific modifications and their unique functions in physiology and pathology are not well understood. The SUMO2/3 paralogues play an important role in proteostasis, converging with ubiquitylation to mediate protein degradation. This function is achieved primarily through SUMO-targeted ubiquitin ligases (STUbLs), which preferentially bind and ubiquitylate poly-SUMO2/3 modified proteins. Effects of the SUMO1 paralogue on protein solubility and aggregation independent of STUbLs and proteasomal degradation have also been reported. Consistent with these functions, sumoylation is implicated in multiple human diseases associated with disturbed proteostasis, and a broad range of pathogenic proteins have been identified as SUMO1 and SUMO2/3 substrates. A better understanding of paralogue-specific functions of SUMO1 and SUMO2/3 in cellular protein quality control may therefore provide novel insights into disease pathogenesis and therapeutic innovation. This review summarizes current understandings of the roles of sumoylation in protein quality control and associated diseases, with a focus on the specific effects of SUMO1 and SUMO2/3 paralogues.

Therapeutic Evaluation of Thermal Heat Shock Response in Mouse Model of Alzheimer’s disease

AbstractBackgroundThe accumulation of toxic amyloid‐ß protein in brain is a hallmark of Alzheimer’s disease. The accumulation of such toxicants is prevented by a cellular protein quality control system. Molecular chaperons, which further prevent proteins from misfolding and aggregating, are produced by this system, which is mostly activated in response to acute thermal stress. This study aims to determine the therapeutic effect of frequent thermal shock on the development of Alzheimer’s diseaseMethodThe induction of Alzheimer’s disease was caused by the intracerebroventricular (ICV) injection of the Aß (1‐42) peptide into the ventricular system of the mouse brain. The animals were divided into four groups: normal control (NC), disease control (DC), sham control (SC), water immersion/no heat group (NH), and hot water immersion/high heat group (HH). The ICV‐Aß injection was given to the DC, NH, and HH groups to induce dementia and AD‐like symptoms. The animals in the HH treatment group were given heat shock in the form of hot water immersion for a period of 4 weeks, where each session lasted for 20 minutes. The animals in the NH group were also exposed to water immersion for 20 minutes daily for a period of 4 weeks, but the water temperature was maintained at room temperature. After the completion of the treatment period, the behavioural and biochemical parameters of the animals were assessed for learning and memory defects. The enzyme‐linked immunosorbent assay (ELISA) was carried out for the Aß estimation.ResultBehavioural assessments in the Y‐maze and morris water maze showed that the animals given daily heat exposure for a period of 4 weeks resisted the detrimental memory effects of the ICV‐Aß injection and had better memory than the water immersion group with no heat treatment given. Increased levels of lipid peroxidation and decreased levels of glutathione were significantly (p<0.05) antagonised by hot water immersion treatment. ELISA showed the lower level of Aß in hot water immersion/high heat group animals when compared to the disease control animals.ConclusionThe study concluded that frequent heat exposure from hot baths and saunas may reduce the risk of developing dementia and Alzheimer’s‐like symptoms in old age.

Neurodegenerative Disease Tauopathies.

Tauopathies are a diverse group of progressive and fatal neurodegenerative diseases characterized by aberrant tau inclusions in the central nervous system. Tau protein forms pathologic fibrillar aggregates that are typically closely associated with neuronal cell death, leading to varied clinical phenotypes including dementia, movement disorders, and motor neuron disease. In this review, we describe the clinicopathologic features of tauopathies and highlight recent advances in understanding the mechanisms that lead to spread of pathologic aggregates through interconnected neuronal pathways. The cell-to-cell propagation of tauopathy is then linked to posttranslational modifications, tau fibril structural variants, and the breakdown of cellular protein quality control.

Novel approaches to determine the functional role of cardiomyocyte specific E3 ligase, Pellino-1 following myocardial infarction

ObjectivesUbiquitination plays a vital role in controlling vascular inflammation, cellular protein quality control, and minimizing misfolded protein toxicity. Pellino-1 (Peli1), a type of E3 ubiquitin ligase, has emerged as a critical regulator of the innate immune response; however, its role in the repair and regeneration of ischemic myocardium remains to be elucidated. MethodsMice (8-12 weeks old, male and females) were divided into (i) Wild type (ii) cardiomyocyte-specific Peli1 overexpressed (AMPEL1Tg/+), (iii) cardiomyocyte-specific Peli1 knockout (CP1KO) and were subjected to sham and left anterior descending artery ligation. The tissues were collected at various time points after surgery for Western blot, and immunohistochemical analyses. Echocardiography is performed 30 days after myocardial infarction. Cardiomyocytes isolated from wild-type, Peli1 overexpressed and knockout mice were used to study the interaction between cardiomyocytes and endothelial cells in vitro under oxidative stress and cells were used for Western blot, flow cytometric analysis, and scratch assay. ResultsWe observed faster wound closure and increased expression of angiogenic factors with MCECs treated with conditioned media obtained from the AMPEL1Tg/+ cardiomyocytes compared to CPIKO and WT cardiomyocytes. Again, AMPEL1Tg/+MI mice showed preserved systolic function and reduced fibrosis compared to the CPIKOMI and WTMI groups. Capillary and arteriolar density were found to be increased in AMPEL1Tg/+MI compared to CP1KOMI. Increased survival and angiogenic factors such as p-Akt, p-MK2, p-IkBα, VEGF, cIAP2, and Bcl2 were observed in AMPEL1Tg/+ compared to CP1KO and WT mice subjected to MI. ConclusionThe present study uncovers the crucial role of cardiac Peli1 as a regulator of the repair and regeneration of ischemic myocardium by using multiple genetically engineered mouse models.

Abstract P2053: Bag5 Plays A Critical Role In The Regulation Of Cellular Homeostasis Through Fine-tuning Of Cellular Protein Quality Control

Background: Cardiac hypertrophy is one of the heart's adaptive responses, which may play a compensatory role in enhancing cardiac function during stress conditions. However, prolonged hypertrophy condition can lead to the progression of cardiac dysfunction and heart failure. Cellular chaperones and co-chaperones play a critical role in maintaining cellular homeostasis by regulating cellular protein quality control. A Bcl2 binding protein BAG5 acts as a co-chaperone to heat shock protein 70 and is known to be upregulated during oxidative stress. A recent study suggests that mutation of the BAG5 gene induces cardiac dysfunction by promoting dilated cardiomyopathy and arrhythmia. However, its role in cardiac hypertrophy is not clear. Method and Results: This study explores the BAG5 function through a protein-protein interaction study by immunoprecipitation and mass spectroscopy. Further, the role of BAG5 in cellular protein quality control and cardiac hypertrophy was tested using cardiomyocytes. Our protein interaction study suggests that BAG5 interacts with several cellular proteins involved in the biological process like Golgi-associated vesicular transport, fatty acid degradation, endoplasmic reticulum-assisted protein folding, chaperone-mediated protein degradation, and deubiquitinating process. Further, we found that knockdown of BAG5 causes induction of cellular hypertrophy, and overexpression of BAG5 reduces PE and ISO-induced cellular hypertrophy. Additionally, we found that BAG5 maintains a balance of cellular protein quality control, and knockdown of BAG5 causes upregulation of cellular autophagy Conclusion: BAG5 plays a critical role in maintaining cellular homeostasis and is protective during cardiac hypertrophy. Additionally, the reduction of BAG5 protein can promote maladaptive autophagy.

Abstract P2116: Role Of Cardiomyocyte Specific Pellino-1, An E3 Ligase On Therapeutic Angiogenesis And Attenuation Of Ventricular Remodeling In A Murine Myocardial Infarction Model

Ubiquitination plays a vital role in our system in controlling vascular inflammation, cellular protein quality control, and minimizing misfolded protein toxicity. Pellino1 (Peli1), a type of E3 ubiquitin ligase, has emerged as a critical regulator of the innate immune response; however, its role in the repair and regeneration of ischemic myocardium remains to be elucidated. Materials: Cardiomyocytes isolated from Wild type (WT), cardiomyocyte-specific Peli1 overexpressed (AMPEL1Tg/+), and cardiomyocyte specific Peli1 knockout (CP1KO) mice were cultured and exposed to 6 h hypoxia, and the conditioned media (CM) collected. CMs were used to treat mouse cardiac endothelial cells (MCECs) followed by H2O2 treatment. Cells were used for Western blot, Flow cytometry, and scratch analyses. For in vivo myocardial infarction (MI) model, animals were exposed to left anterior descending artery (LAD) ligation. Animals were divided into (a) WT, (b) AMPEL1Tg/+(c) CP1KO and subjected to sham (S) and MI. Results: In vitro study documented faster wound closure and increased expression of angiogenic factors (pFlk-1, Ang-1 and VEGF) with MCECs treated with CM obtained from AMPEL1 compared to the other CM obtained from CP1KO and WT. There was no change in cardiac functions between Sham groups. AMPEL1Tg/+ MI group, showed preserved systolic functions, represented by both EF [n=12-14, p<0.0001] and FS [n=12-14, p<0.0001] compared to WTMI. However, CP1KO MI showed loss of systolic function, as represented by EF [n=13, p=0.03] and FS [n=13, p=0.03] compared to WTMI. The extent of fibrosis is also reduced in AMPEL1MI [n=5, p=0.0031], but increased in CP1KOMI [n=6-7, p<0.0001] compared to WTMI. Capillary n=4-5, p=0.0010] and arteriolar density [n=5, p=0.0005] were increased in AMPEL1MI but reduced in CP1KOMI [n=6, p<0.0001]; [n=5-7, p=0.02] compared to WTMI. Western blot analysis documented increased survival and angiogenic factors (pAKT, VEGF, and Bcl2) in AMPEL1MI compared to CP1KOMI and WTMI. Conclusion: Our study uncovers the role of cardiomyocyte-specific Peli1 as a regulator of repair and regeneration of ischemic myocardium, as evidenced by preserved cardiac function, increased expression of angiogenic factors, and reduction of apoptotic markers in the MI model.

BAG3 Overexpression Attenuates Ischemic Stroke Injury by Activating Autophagy and Inhibiting Apoptosis.

The ubiquitin-proteasome system (UPS) and autophagy are 2 major protein degradation pathways in eukaryotic cells. We previously identified a switch from UPS to autophagy with changes in BAG3 (B-cell lymphoma 2-associated-athanogene 3) expression after cerebral ischemia in mice. BAG3 is an antiapoptotic-cochaperone that is directly involved in cellular protein quality control as a mediator for selective macroautophagy. Here, we aimed to investigate the role of BAG3 in ischemic stroke. Middle cerebral artery occlusion/reperfusion (MCAO/R) and oxygen-glucose deprivation/reoxygenation were used to mimic cerebral ischemia in vivo and in vitro. The UPS inhibitor MG132 and autophagy inhibitor 3-MA (3-methyladenine) were administered to mice to identify how BAG3 was involved after MCAO/R. Adeno-associated virus and lentiviral vector were used to regulate BAG3 expression in vivo and in vitro, respectively. Behavioral tests, 2,3,5-triphenyltetrazolium chloride staining, and Hematoxylin & Eosin staining were performed to evaluate cerebral injury following MCAO/R, and a Cell Counting kit-8 assay was conducted to assess oxygen-glucose deprivation/reoxygenation-induced injury in cells. Brain tissues and cell lysates were collected and analyzed for UPS activation, autophagy, and apoptosis. The UPS inhibitor alleviated MCAO injury in mice and increased autophagy and BAG3 expression, whereas the autophagy inhibitor exacerbated MCAO/R-induced injury. In addition, BAG3 overexpression significantly improved neurological outcomes, reduced infarct volume in vivo, and enhanced cell survival by activating autophagy and suppressing apoptosis in vitro. Our findings indicate that BAG3 overexpression activates autophagy and inhibits apoptosis to prevent cerebral ischemia/reperfusion and hypoxia/reoxygenation injury, suggesting a potential therapeutic benefit of BAG3 expression in cerebral ischemia.

1768-P: Sel1L-Hrd1 Endoplasmic Reticulum-Associated Degradation Regulates PC2 Function and Proglucagon Processing in Islet α-Cells

Pancreatic islets rely on cellular protein quality control to maintain glucoregulatory hormone production. Proglucagon, precursor of glucagon and glucagon-like peptide 1 (GLP1), is expressed in islet α cells, intestinal L-cells, and some neurons. Islet α cells predominantly convert proglucagon to glucagon through prohormone convertase 2 (PC2). Islet-derived GLP1 is increasingly recognized as an important contributor to islet function, but the factors controlling its production remain unclear. To understand how protein quality control affects proglucagon processing in α cells, we inactivated the highly conserved Sel1L-Hrd1 endoplasmic reticulum-associated degradation (ERAD) system using Cre-loxP recombination in mice. Compared to littermate controls, Sel1LΔGcg mice showed an age-related decline in glucagon secretion in vivo, associated with a 43% decrease in pancreatic glucagon content (76.1 +/- 14.1 vs. 134.4 +/- 14.9 ng/g). Pancreatic GLP1 content was unchanged in Sel1LΔGcg mice (779.4 +/- 60.7 vs. 773.4 +/- 128.6 pg/g), despite a 37% reduction in α cell mass (0.19 +/- 0.04 vs. 0.12 +/- 0.04 mg/pancreas). Expression of the precursor form of PC2 (proPC2) was increased in Sel1LΔGcg α cells, suggesting accumulation of misfolded protein and/or impaired maturation. To investigate the mechanism underlying these changes, we used CRISPR to delete Sel1L in αTC cells. ERAD-deficient αTC-ΔSel1L cells showed 1.75-fold higher expression of proPC2, in addition to appearance of a novel truncated (~56 kD) form of proPC2. Though expression of the mature (64 kD) PC2 form was unchanged in αTC-ΔSel1L cells, PC2 activity was reduced by half in a specific enzyme assay. This was accompanied by decreased expression of 7B2, a chaperone required for proPC2 transit and activation in the secretory pathway. These data show that Sel1L-Hrd1 ERAD is required to ensure proper proPC2 maturation and glucagon production in α cells, thus maintaining classic α cell identity. Disclosure R.B.Reinert: None. W.Zhu: None. L.Pan: None. A.Russo: None. R.Ray: None. N.Shrestha: None. I.Lindberg: None. L.Qi: None. Funding National Institutes of Health (K08DK129719, T32DK007245)

The Cdc48 N-terminal domain has a molecular switch that mediates the Npl4-Ufd1-Cdc48 complex formation

Cdc48 (VCP/p97) is a major AAA-ATPase involved in protein quality control, along with its canonical cofactors Ufd1 and Npl4 (UN). Here, we present novel structural insights into the interactions within the Cdc48-Npl4-Ufd1 ternary complex. Using integrative modeling, we combine subunit structures with crosslinking mass spectrometry (XL-MS) to map the interaction between Npl4 and Ufd1, alone and in complex with Cdc48. We describe the stabilization of the UN assembly upon binding with the N-terminal-domain (NTD) of Cdc48 and identify a highly conserved cysteine, C115, at the Cdc48-Npl4-binding interface which is central to the stability of the Cdc48-Npl4-Ufd1 complex. Mutation of Cys115 to serine disrupts the interaction between Cdc48-NTD and Npl4-Ufd1 and leads to a moderate decrease in cellular growth and protein quality control in yeast. Our results provide structural insight into the architecture of the Cdc48-Npl4-Ufd1 complex as well as its invivo implications.

An NMR Study of a 300-kDa AAA+ Unfoldase

AAA+ ATPases are ubiquitous hexameric unfoldases acting in cellular protein quality control. In complex with proteases, they form protein degradation machinery (the proteasome) in both archaea and eukaryotes. Here, we use solution-state NMR spectroscopy to determine the symmetry properties of the archaeal PAN AAA+ unfoldase and gain insights into its functional mechanism. PAN consists of three folded domains: the coiled-coil (CC), OB and ATPase domains. We find that full-length PAN assembles into a hexamer with C2 symmetry, and that this symmetry extends over the CC, OB and ATPase domains. The NMR data, collected in the absence of substrate, are incompatible with the spiral staircase structure observed in electron-microscopy studies of archaeal PAN in the presence of substrate and in electron-microscopy studies of eukaryotic unfoldases both in the presence and in the absence of substrate. Based on the C2 symmetry revealed by NMR spectroscopy in solution, we propose that archaeal ATPases are flexible enzymes, which can adopt distinct conformations in different conditions. This study reaffirms the importance of studying dynamic systems in solution.

Selection and evolution of disulfide-rich peptides via cellular protein quality control.

Disulfide-rich peptides (DRPs) are an interesting and promising molecular format for drug discovery and development. However, the engineering and application of DRPs rely on the foldability of the peptides into specific structures with correct disulfide pairing, which strongly hinders the development of designed DRPs with randomly encoded sequences. Design or discovery of new DRPs with robust foldability would provide valuable scaffolds for developing peptide-based probes or therapeutics. Herein we report a cell-based selection system leveraging cellular protein quality control (termed PQC-select) to select DRPs with robust foldability from random sequences. By correlating the foldability of DRPs with their expression levels on the cell surface, thousands of sequences that can fold properly have been successfully identified. We anticipated that PQC-select will be applicable to many other designed DRP scaffolds in which the disulfide frameworks and/or the disulfide-directing motifs can be varied, enabling the generation of a variety of foldable DRPs with new structures and superior potential for further developments.

Identification of subfunctionalized aggregate-remodeling J-domain proteins in Arabidopsis thaliana.

J-domain proteins (JDPs) are critical components of the cellular protein quality control machinery, playing crucial roles in preventing the formation and, solubilization of cytotoxic protein aggregates. Bacteria, yeast, and plants additionally have large, multimeric heat shock protein 100 (Hsp100)-class disaggregases that resolubilize protein aggregates. JDPs interact with aggregated proteins and specify the aggregate-remodeling activities of Hsp70s and Hsp100s. However, the aggregate-remodeling properties of plant JDPs are not well understood. Here we identify eight orthologs of Sis1 (an evolutionarily conserved Class II JDP of budding yeast) in Arabidopsis thaliana with distinct aggregate-remodeling functionalities. Six of these JDPs associate with heat-induced protein aggregates in vivo and co-localize with Hsp101 at heat-induced protein aggregate centers. Consistent with a role in solubilizing cytotoxic protein aggregates, an atDjB3 mutant had defects in both solubilizing heat-induced aggregates and acquired thermotolerance as compared with wild-type seedlings. Next, we used yeast prions as protein aggregate models to show that the six JDPs have distinct aggregate-remodeling properties. Results presented in this study, as well as findings from phylogenetic analysis, demonstrate that plants harbor multiple, evolutionarily conserved JDPs with capacity to process a variety of protein aggregate conformers induced by heat and other stressors.

Volleying plasma membrane proteins from birth to death: Role of J-domain proteins.

The function, stability, and turnover of plasma membrane (PM) proteins are crucial for cellular homeostasis. Compared to soluble proteins, quality control of plasma membrane proteins is extremely challenging. Failure to meet the high quality control standards is detrimental to cellular and organismal health. J-domain proteins (JDPs) are among the most diverse group of chaperones that collaborate with other chaperones and protein degradation machinery to oversee cellular protein quality control (PQC). Although fragmented, the available literature from different models, including yeast, mammals, and plants, suggests that JDPs assist PM proteins with their synthesis, folding, and trafficking to their destination as well as their degradation, either through endocytic or proteasomal degradation pathways. Moreover, some JDPs interact directly with the membrane to regulate the stability and/or functionality of proteins at the PM. The deconvoluted picture emerging is that PM proteins are relayed from one JDP to another throughout their life cycle, further underscoring the versatility of the Hsp70:JDP machinery in the cell.

PSMA2 knockdown impacts expression of proteins involved in immune and cellular stress responses in human lung cells

Proteasome subunit alpha type-2 (PSMA2) is a critical component of the 20S proteasome, which is the core particle of the 26S proteasome complex and is involved in cellular protein quality control by recognizing and recycling defective proteins. PSMA2 expression dysregulation has been detected in different human diseases and viral infections. No study yet has reported PSMA2 knockdown (KD) effects on the cellular proteome. Methods: We used SOMAScan, an aptamer-based multiplexed technique, to measure >1300 human proteins to determine the impact of PSMA2 KD on A549 human lung epithelial cells. Results: PSMA2 KD resulted in significant dysregulation of 52 cellular proteins involved in different bio-functions, including cellular movement and development, cell death and survival, and cancer. The immune system and signal transduction were the most affected cellular functions. PSMA2 KD caused dysregulation of several signaling pathways involved in immune response, cytokine signaling, organismal growth and development, cellular stress and injury (including autophagy and unfolded protein response), and cancer responses. Conclusions: In summary, this study helps us better understand the importance of PSMA2 in different cellular functions, signaling pathways, and human diseases.

Altered Cellular Protein Quality Control System Modulates Cardiomyocyte Function in Volume Overload-Induced Hypertrophy.

Volume-induced hypertrophy is one of the risk factors for cardiac morbidity and mortality. In addition, mechanical and metabolic dysfunction, aging, and cellular redox balance are also contributing factors to the disease progression. In this study, we used volume overload (VO), which was induced by an aortocaval fistula in 2-month-old male Wistar rats, and sham-operated animals served as control. Functional parameters were measured by transthoracic echocardiography at termination 4- or 8-months after VO. The animals showed hypertrophic remodeling that was accompanied by mechanical dysfunction and increased cardiomyocyte stiffness. These alterations were reversible upon treatment with glutathione. Cardiomyocyte dysfunction was associated with elevated oxidative stress markers with unchanged inflammatory signaling pathways. In addition, we observed altered phosphorylation status of small heat shock proteins 27 and 70 and diminished protease expression caspases 3 compared to the matched control group, indicating an impaired protein quality control system. Such alterations might be attributed to the increased oxidative stress as anticipated from the enhanced titin oxidation, ubiquitination, and the elevation in oxidative stress markers. Our study showed an early pathological response to VO, which manifests in cardiomyocyte mechanical dysfunction and dysregulated signaling pathways associated with enhanced oxidative stress and an impaired protein quality control system.

The Interplay between Finasteride-Induced Androgen Imbalance, Endoplasmic Reticulum Stress, Oxidative Stress, and Liver Disorders in Paternal and Filial Generation.

Finasteride (Fin) causes androgen imbalance by inhibiting the conversion of testosterone (T) to its more active metabolite, dihydrotestosterone (DHT). Androgen receptors (AR) are present (e.g., in hepatocytes), which have well-developed endoplasmic reticulum (ERet). Cellular protein quality control is carried out by ERet in two paths: (i) unfolded protein response (UPR) and/or (ii) endoplasmic reticulum associated degradation (ERAD). ERet under continuous stress can generate changes in the UPR and can direct the cell on the pathway of life or death. It has been demonstrated that genes involved in ERet stress are among the genes controlled by androgens in some tissues. Oxidative stress is also one of the factors affecting the functions of ERet and androgens are one of the regulators of antioxidant enzyme activity. In this paper, we discuss/analyze a possible relationship between androgen imbalance in paternal generation with ERet stress and liver disorders in both paternal and filial generation. In our rat model, hyperglycemia and subsequent higher accumulation of hepatic glycogen were observed in all filial generation obtained from females fertilized by Fin-treated males (F1:Fin). Importantly, genes encoding enzymes involved in glucose and glycogen metabolism have been previously recognized among UPR targets.

Inhibition of the dopamine transporter promotes lysosome biogenesis and ameliorates Alzheimer's disease-like symptoms in mice.

Lysosomes are degradative organelles that maintain cellular homeostasis and protein quality control. Transcription factor EB (TFEB)-mediated lysosome biogenesis enhances lysosome-dependent degradation and alleviates neurodegenerative diseases, but the mechanisms underlying TFEB regulation and modification are still poorly understood. By screening novel small-molecule compounds, we identified a group of lysosome-enhancing compounds (LYECs) that promote TFEB activation and lysosome biogenesis. One of these compounds, LH2-051, significantly inhibited the function of the dopamine transporter (DAT) and subsequently promoted lysosome biogenesis. We uncovered cyclin-dependent kinase 9 (CDK9) as a novel regulator of DAT-mediated lysosome biogenesis and identified six novel CDK9-phosphorylated sites on TFEB. We observed that signal transduction by the DAT-CDK9-TFEB axis occurs on lysosomes. Finally, we found that LH2-051 enhanced the degradation of amyloid beta plaques and improved the memory of amyloid precursor protein (APP)/Presenilin 1 (PS1) mice. We identified the DAT-CDK9-TFEB signaling axis as a novel regulator of lysosome biogenesis. Our study sheds light on the mechanisms of protein quality control under pathophysiological conditions.