Regulation Of Folding Research Articles

Secretory Nogo-B regulates Th2 differentiation in the lung cancer microenvironment

Nogo-B, a ubiquitously expressed member of the reticulon family, plays an important role in maintaining endoplasmic reticulum (ER) structure, regulating protein folding, and calcium homeostasis. In this study, we demonstrate that Nogo-B expression and secretion are upregulated in lung cancer and correlate to overall survival. Nogo-B is secreted by various cells, particularly lung cancer cells. ER stress and phosphorylation at serine 107 can induce Nogo-B secretion. Secretory Nogo-B suppresses the differentiation of Th2 cells and the release of type 2 cytokines, thus influencing the anti-tumor effects of Th2-related immune cells, including IgE+B cell class switching and eosinophil activation.

The Role of Protein Quantity Control in Polyglutamine Spinocerebellar Ataxias.

Polyglutamine spinocerebellar ataxias (polyQ SCAs) represent the most prevalent subtype of SCAs. The primary pathogenic mechanism is believed to be the gain-of-function neurotoxicity of polyQ proteins. Strategies such as enhancing the degradation or inhibiting the accumulation of these mutant proteins are pivotal for reducing their toxicity and slowing disease progression. The protein quality control (PQC) system, comprising primarily molecular chaperones and the ubiquitin‒proteasome system (UPS), is essential for maintaining protein homeostasis by regulating protein folding, trafficking, and degradation. Notably, polyQ proteins can disrupt the PQC system by sequestering its critical components and impairing its proteasomal functions. Therefore, restoring the PQC system through genetic or pharmacological interventions could potentially offer beneficial effects and alleviate the symptoms of the disease. Here, we will provide a review on the distribution, expression, and genetic or pharmacological intervention of protein quality control system in cellular or animal models of PolyQ SCAs.

Exercise mitigates reductive stress-induced cardiac remodeling in mice

The endoplasmic reticulum (ER) regulates protein folding and maintains proteostasis in cells. We observed that the ER transcriptome is impaired during chronic reductive stress (RS) in cardiomyocytes. Here, we hypothesized that a prolonged moderate treadmill exercise mitigates the RS-induced ER dysfunction and cardiac remodeling in cardiac-specific constitutively active Nrf2 mice (CaNrf2-TG). RNA sequencing showed notable alterations in the ER transcriptome of TG hearts at 4, 12, and 24 weeks (16, 28, and 35 genes, respectively). Notably, the downregulation of ER genes was significant at 12 weeks, and further pronounced at 24 weeks, at which the cardiac pathology is evident. We also observed increased levels of ubiquitinated proteins in CaNrf2-TG hearts across all ages, along with VCP, a marker of ERAD function, at 24 weeks. These findings indicate that constitutive Nrf2 activation and RS impair protein-folding activity and augments ERAD function over time. Exercise intervention for 20 weeks (beginning at 6 weeks of age), reduced cardiomyocyte hypertrophy (from 448 μm2 to 280 μm2) in TG mice, through adaptive remodeling, and preserved the cardiac function. However, while exercise did not influence antioxidants or ER stress protein levels, it significantly improved ERAD function and autophagy flux (LC-I to LC-II) in the TG-EXE hearts. Collectively, our findings underscore the prophylactic potential of exercise in mitigating RS-associated pathology, highlighting its essential role in maintaining cellular proteostasis through ER-independent mechanisms.

A prospective study of the proteome of equine pre-implantation embryo.

The present study was conducted to investigate the global proteome of 8-day-old equine blastocysts. Follicular dynamics of eight adult mares were monitored by ultrasonography and inseminated 24 h after the detection of a preovulatory follicle. Four expanded blastocysts were recovered, pooled, and subjected to protein extraction and mass spectrometry. Protein identification was conducted based on four database searches (PEAKS, Proteome Discoverer software, SearchGUI software, and PepExplorer). Enrichment analysis was performed using g:Profiler, Panther, and String platforms. After the elimination of identification redundancies among search tools (at three levels, based on identifiers, peptides, and cross-database mapping), 1977 proteins were reliably identified in the samples of equine embryos. Proteomic analysis unveiled robust metabolic activity in the 8-day equine embryo, highlighted by an abundance of proteins engaged in key metabolic pathways like the TCA cycle, ATP biosynthesis, and glycolysis. The prevalence of chaperones among highly abundant proteins suggests that regulation of protein folding, and degradation is a key process during embryo development. These findings pave the way for developing new strategies to improve equine embryo media and optimize invitro fertilization techniques.

Systematic Investigation of the Trafficking of Glycoproteins on the Cell Surface

Glycoproteins located on the cell surface play a pivotal role in nearly every extracellular activity. N-glycosylation is one of the most common and important protein modifications in eukaryotic cells, and it often regulates protein folding and trafficking. Glycosylation of cell-surface proteins undergoes meticulous regulation by various enzymes in the endoplasmic reticulum (ER) and the Golgi, ensuring their proper folding and trafficking to the cell surface. However, the impacts of protein N-glycosylation, N-glycan maturity, and protein folding status on the trafficking of cell-surface glycoproteins remain to be explored. In this work, we comprehensively and site-specifically studied the trafficking of cell-surface glycoproteins in human cells. Integrating metabolic labeling, bioorthogonal chemistry, and multiplexed proteomics, we investigated 706 N-glycosylation sites on 396 cell-surface glycoproteins in monocytes, either by inhibiting protein N-glycosylation, disturbing N-glycan maturation, or perturbing protein folding in the ER. The current results reveal their distinct impacts on the trafficking of surface glycoproteins. The inhibition of protein N-glycosylation dramatically suppresses the trafficking of many cell-surface glycoproteins. The N-glycan immaturity has more substantial effects on proteins with high N-glycosylation site densities, while the perturbation of protein folding in the ER exerts a more pronounced impact on surface glycoproteins with larger sizes. Furthermore, for N-glycosylated proteins, their trafficking to the cell surface is related to the secondary structures and adjacent amino acid residues of glycosylation sites. Systematic analysis of surface glycoprotein trafficking advances our understanding of the mechanisms underlying protein secretion and surface presentation.

Protein G-quadruplex interactions and their effects on phase transitions and protein aggregation.

The SERF family of proteins were originally discovered for their ability to accelerate amyloid formation. Znf706 is an uncharacterized protein whose N-terminus is homologous to SERF proteins. We show here that human Znf706 can promote protein aggregation and amyloid formation. Unexpectedly, Znf706 specifically interacts with stable, non-canonical nucleic acid structures known as G-quadruplexes. G-quadruplexes can affect gene regulation and suppress protein aggregation; however, it is unknown if and how these two activities are linked. We find Znf706 binds preferentially to parallel G-quadruplexes with low micromolar affinity, primarily using its N-terminus, and upon interaction, its dynamics are constrained. G-quadruplex binding suppresses Znf706's ability to promote protein aggregation. Znf706 in conjunction with G-quadruplexes therefore may play a role in regulating protein folding. RNAseq analysis shows that Znf706 depletion specifically impacts the mRNA abundance of genes that are predicted to contain high G-quadruplex density. Our studies give insight into how proteins and G-quadruplexes interact, and how these interactions affect both partners and lead to the modulation of protein aggregation and cellular mRNA levels. These observations suggest that the SERF family of proteins, in conjunction with G-quadruplexes, may have a broader role in regulating protein folding and gene expression than previously appreciated.

Modulators of MAPK pathway activity during filamentous growth in Saccharomyces cerevisiae.

Mitogen-activated protein kinase (MAPK) pathways control the response to intrinsic and extrinsic stimuli. In the budding yeast Saccharomyces cerevisiae, cells undergo filamentous growth, which is regulated by the fMAPK pathway. To better understand the regulation of the fMAPK pathway, a genetic screen was performed to identify spontaneous mutants with elevated activity of an fMAPK pathway-dependent growth reporter (ste4 FUS1-HIS3). In total, 159 mutants were isolated and analyzed by secondary screens for invasive growth by the plate-washing assay and filament formation by microscopy. Thirty-two mutants were selected for whole-genome sequencing, which identified new alleles in genes encoding known regulators of the fMAPK pathway. These included gain-of-function alleles in STE11, which encodes the MAPKKK, as well as loss-of-function alleles in KSS1, which encodes the MAP kinase, and loss-of-function alleles in RGA1, which encodes a GTPase-activating protein (GAP) for CDC42. New alleles in previously identified pathway modulators were also uncovered in ALY1, AIM44, RCK2, IRA2, REG1, and in genes that regulate protein folding (KAR2), glycosylation (MNN4), and turnover (BLM10). Mutations leading to C-terminal truncations in the transcription factor Ste12p were also uncovered that resulted in elevated reporter activity, identifying an inhibitory domain of the protein from residues 491 to 688. We also find that a diversity of filamentous growth phenotypes can result from combinatorial effects of multiple mutations and by loss of different regulators of the response. The alleles identified here expand the connections surrounding MAPK pathway regulation and reveal new features of proteins that function in the signaling cascade.

"Sticki-ER": Functions of the Platelet Endoplasmic Reticulum.

Significance: The primary role of platelets is to generate a thrombus by platelet activation. Platelet activation relies on calcium mobilization from the endoplasmic reticulum (ER). ER resident proteins, which are externalized upon platelet activation, are essential for the function of platelet surface receptors and intercellular interactions. Recent Advances: The platelet ER is a conduit for changes in cellular function in response to the extracellular milieu. ER homeostasis is maintained by an appropriate redox balance, regulated calcium stores and normal protein folding. Alterations in ER function and ER stress results in ER proteins externalizing to the cell surface, including members of the protein disulfide isomerase family (PDIs) and chaperones. Critical Issues: The platelet ER is central to platelet function, but our understanding of its regulation is incomplete. Previous studies have focused on the function of PDIs in the extracellular space, and much less on their intracellular role. How platelets maintain ER homeostasis and how they direct ER chaperone proteins to facilitate intercellular signalling is unknown. Future Directions: An understanding of ER functions in the platelet is essential as these may determine critical platelet activities such as secretion and adhesion. Studies are necessary to understand the redox reactions of PDIs in the intracellular versus extracellular space, as these differentially affect platelet function. An unresolved question is how platelet ER proteins control calcium release. Regulation of protein folding in the platelet and downstream pathways of ER stress require further evaluation. Targeting the platelet ER may have therapeutic application in metabolic and neoplastic disease.

Uloga glikoproteina 96 u karcinomu dojke

Glycoprotein 96 (gp96) is a member of the heat shock protein 90 family, which is an ubiquitous family of molecular chaperones that are involved in the regulation of protein folding and other essential cellular activities. Residing in the lumen of the endoplasmic reticulum, gp96 plays a key role in maintaining protein homeostasis, from assemblage to degradation. However, exposure to stressful conditions that disturb cellular homeostasis may translocate gp96 to the cell surface, which implies its additional functions, such as the regulation of intracellular signalling, proliferation, and apoptosis, as well as the modulation of the immune response. Besides its roles under physiological conditions, gp96 is also included in different stages of oncogenesis. In this review, we summarised available data on the structure, physiological, and pathophysiological roles of gp96, particularly in breast cancer oncogenesis.

Toxic effect of chromium on nonspecific immune, bioaccumulation, and tissue structure of Urechis unicinctus.

The contamination of toxic heavy metals in aquatic environments has garnered significant global attention due to its detrimental effects on marine organisms and human health. Hexavalent chromium is a typical environmental and occupational heavy metal pollutant, identified as carcinogenic heavy metal. This study aimed to assess the impact of different Cr (VI) concentrations (0.05-2.5 mg/L) on Urechis unicinctus (U. unicinctus) by investigating bioaccumulation, antioxidant defense system, expression of resistance-related genes, and histological issues. A clear concentration-effect relationship was observed in the bioaccumulation of Cr (VI) in muscle tissues of U. unicinctus. Moreover, exposure to Cr (VI) can alter the activities of lysozyme (LSZ), catalase (CAT), and superoxide dismutase (SOD) to enhance cellular defense mechanisms in U. unicinctus. Likewise, maintained the normal protein structure and functional stability by regulating protein folding. The heat shock cognitive protein (HSC70) gene showed an upward and then downward trend after Cr (VI) exposure. At 12 h, the HSC70 gene expression reached the maximum values of 4.75 and 4.61-fold in the 0.1 and 1.5 mg/L groups, respectively. The organism produced a large number of free radicals, and elevated level of metallothionein (MT) was used to scavenge free radicals and alleviate oxidative stress. Additionally, histopathological examination revealed disorganization in the midgut, atrophic changes in intestinal connective tissue, uneven distribution in respiratory tissues, and irregular shape with a significant reduction in epithelial cells within the gastric cavity. These findings can serve as a valuable reference for elucidating the toxicity mechanisms of heavy metals towards marine benthic organisms and enhancing water environment monitoring strategies.

Regulation of Epithelial and Endothelial Barriers by Molecular Chaperones.

The integrity and permeability of epithelial and endothelial barriers depend on the formation of tight junctions, adherens junctions, and a junction-associated cytoskeleton. The establishment of this junction-cytoskeletal module relies on the correct folding and oligomerization of its protein components. Molecular chaperones are known regulators of protein folding and complex formation in different cellular compartments. Mammalian cells possess an elaborate chaperone network consisting of several hundred chaperones and co-chaperones. Only a small part of this network has been linked, however, to the regulation of intercellular adhesions, and the systematic analysis of chaperone functions at epithelial and endothelial barriers is lacking. This review describes the functions and mechanisms of the chaperone-assisted regulation of intercellular junctions. The major focus of this review is on heat shock protein chaperones, their co-chaperones, and chaperonins since these molecules are the focus of the majority of the articles published on the chaperone-mediated control of tissue barriers. This review discusses the roles of chaperones in the regulation of the steady-state integrity of epithelial and vascular barriers as well as the disruption of these barriers by pathogenic factors and extracellular stressors. Since cytoskeletal coupling is essential for junctional integrity and remodeling, chaperone-assisted assembly of the actomyosin cytoskeleton is also discussed.

Photoacid Generators for Biomedical Applications.

Photoacid generators (PAGs) are compounds capable of producing hydrogen protons (H+ ) upon irradiation, including irreversible and reversible PAGs, which have been widely studied in photoinduced polymerization and degradation for a long time. In recent years, the applications of PAGs in the biomedical field have attracted more attention due to their promising clinical value. So, an increasing number of novel PAGs have been reported. In this review, the recent progresses of PAGs for biomedical applications is systematically summarized, including tumor treatment, antibacterial treatment, regulation of protein folding and unfolding, control of drug release and so on. Furthermore, a concept of water-dependent reversible photoacid (W-RPA) and its antitumor effect are highlighted. Eventually, the challenges of PAGs for clinical applications are discussed.

Single-Cell Transcriptional Survey of the Initiation, Propagation and Maintenance of the Intestinal Graft-Versus-Host Disease

Background: Graft-versus-host disease (GVHD) is a life-threatening complication of hematopoietic stem cell transplantation (HSCT). The intestine not only is a primary target of immune attack, but also regulates the severity of systematic GVHD. Although the critical roles of immune cells in GVHD have been documented, the dynamic changes of cell populations, and cell-associated transcriptional signatures during immune attack and epithelial regeneration remain elusive. Methods: To better characterize disease progression, tissues were harvested from murine intestine suffering from GVHD (GVHD_D3, GVHD_D10, GVHD_D21), coupled with irradiated and repaired samples (BM_D3, BM_D10, BM_D21), and healthy control (CON). Each sample mixed with segments of proximal and distal small intestine from three mice. Tissues were dissociated into single-cell suspensions and processed using the 10x Genomics Chromium workflow. After data pre-processing and quality control, we profiled 69242 individual cells from 7 samples. Results: Uniform manifold approximation and projection (UMAP) analysis yielded 17 clusters, including 8 types of epithelial cells, 8 types of immune cells and 1 type of stroma cell. In healthy mice, epithelial cells were highly enriched in murine small intestine, taking up 79.31% of total cells: differentiated enterocytes (EC) (59.31%) represented the largest cohort of epithelial cells, while intestinal stem cells (ISC), trans-amplifying (TA) cells and enterocyte progenitor (EP) only occupied very small portions. In mucosal immune system, the abundance of T cells (9.91%) and B cells (10.43%) was much higher than that of ILC, macrophage and neutrophils. Upon radiation and the development of GVHD, cell populations of murine small intestine dramatically changed. Three days after transplantation, the proportion of ECs dramatically dropped. On the contrast, ɣδ T cells and ILC rapidly accumulated in the damaged intestine. From day 3 to day 10, we observed a steep decrease in ɣδ T cells from samples of BM and GVHD group. At our last observation, BM resorted its epithelial components, while GVHD had a great abundance of T cells (41.73%) and a lower level of differentiated ECs (36.90%). In epithelial components, a total of 44468 epithelial cells were subclustered them into 22 subsets. ISC serves as the production department, which was enriched in mitochondrial genes and genes regulating protein folding. The cluster TA_1 from D21 samples was enriched in pathway related to structure organization and BMP signals, which is required for the initiation of intestinal differentiation and morphogenesis. At day 3, a rapid expansion of subsets of TA_2 and Regenerative progenitors caught our attention. Metabolic pathways such as tryptophan catabolic process, arachidonic acid secretion, methionine metabolic process were highly correlated with wound healing and cell proliferation. EP_1 emerging at day 3 majored in material transportation. EP in samples from control and BM (EP_2) was able to repair DNA damage, while EP_3 that mostly detected in GVHD sample were involved in metabolic disorders, which may explain its deficiency in EC differentiation. T cells and ILC were divided into 16 subsets. In addition to its well-known effects in host defense, several genes that expressed in γδT cells are essential for maintaining intestinal homeostasis. The Tgfb3-Vegfa+ subset regulated microvillus organization and intestinal absorption; the Tgfb3-Vegfa- subset participated in sensory and ciliary movement. At day3, the above clusters undergone a rapid expansion, suggesting an enhanced protective role of γδT cells in the early period of transplantation. We also identified different subtypes of T cells between BM and GVHD samples. Two clusters of cycling CD8+ T cells were more enriched in GVHD samples, which also express high levels of cytotoxic markers. While in BM, we found two clusters of anergic T cells without expression of markers of naïve, memory, effector and exhaustion. The double positive T cells in GVHD may regulate immune infiltration, while the CD4+ Th2-like cell in BM may link to immunoglobin production and Treg differentiation. Conclusions: Single-Cell transcriptional analysis revealed that different cell populations between BM and GVHD. T cells in GVHD were highly-proliferative and cytotoxic, and epithelial cells in GVHD had metabolic disorder and were resistant to enterocyte differentiation.

Electrostatic and hydrophobic interaction cooperative nanochaperone regulates protein folding

AbstractNatural molecular chaperones utilize spatially ordered multiple molecular forces to effectively regulate protein folding. However, synthesis of such molecules is a big challenge. The concept of “aggregate science” provides insights to construct chemical entities (aggregates) beyond molecular levels to mimic both the structure and function of natural chaperone. Inspired by this concept, herein we fabricate a novel multi‐interaction (i.e., electrostatic and hydrophobic interaction) cooperative nanochaperone (multi‐co‐nChap) to regulating protein folding. This multi‐co‐nChap is fabricated by rationally introducing electrostatic interactions to the surface (corona) and confined hydrophobic microdomains (shell) of traditional single‐hydrophobic interaction nanochaperone. We demonstrate that the corona electrostatic attraction facilitates the diffusion of clients into the hydrophobic microdomains, while the shell electrostatic interaction balances the capture and release of clients. By finely synergizing corona electrostatic attraction with shell electrostatic repulsion and hydrophobic interaction, the optimized multi‐co‐nChap effectively facilitated de novo folding of nascent polypeptides. Moreover, the synergy between corona electrostatic attraction, shell electrostatic attraction and shell hydrophobic interaction significantly enhanced the capability of multi‐co‐nChap to protect native proteins from denaturation at harsh temperatures. This work provides important insights for understanding and design of nanochaperone, which is a kind of ordered aggregate with chaperone‐like activity that beyond the level of single molecule.

Abstract P2066: Forced Exercise Prevents Reductive Stress Induced Cardiomyocyte Remodeling And Cardiac Dysfunction

Background: Disruption of the endoplasmic reticulum (ER) function has been recognizedas a clinical signature of congestive heart failure, ischemia, and atherosclerosis. Whilepro-oxidative redox milieu is vital for the ER to regulate protein folding events. Recently,we reported that overabundant antioxidants in the heart cause reductive stress (RS) andimpair the protein folding mechanisms due to unresolved ER stress. Here, we testedwhether forced exercise prevents RS and improves ER function through augmenting ROSsignaling, thereby improving the PQC mechanisms in the heart. Methods: Cardiac-specific constitutively active Nrf2 (CaNrf2-TG) and non-transgenic (NTG) mice at 5-6weeks of age were subjected to forced treadmill exercise (FTE) for 20 weeks (15meters/minute with a 5° slope; for 45 minutes/day; for 6 days every week). Cardiacstructure and function were analyzed before and after the exercise. At 22 weeks, micewere sacrificed for analysis to assess the benefits of FTE. Results: RNA sequencingrevealed significant downregulation of key protein folding genes and chaperones in TGmice in association with the pathological remodeling at 6 months. Particularly, Pdi, Atf6, Calr, and Ero1α were downregulated (>2 fold) at 24 weeks in TG mice, indicating impairedER function in the remodeling hearts. These changes were coupled with increasedcardiomyocyte size and hypertrophy. Upon FTE, we observed significant improvementsin the structure and function of the cardiomyocytes. WGA staining showed the cross-section area of the cardiomyocytes was significantly reduced in the exercise groupcompared to the sedentary-TG mice experiencing cellular hypertrophy (115.7μm 2 NTGvs 428.8μm 2 TG vs 202.5 μm 2 TG-FTE). Echocardiography analysis demonstratedpreservation of cardiac structure and function (EF, FS, IVD, IVS, EDV, and ESV).Specifically, compensatory improvement in diastolic function (MVE/A ratio) was observedin TG-FTE exe group. Additionally, we observed that the ubiquitination of proteins wassignificantly reduced in the exercise group indicating deaccumulation of the misfoldedproteins in RS hearts. Conclusion: Together these results demonstrate that chronicexercise could ameliorate RS-induced ER stress and cardiac dysfunction.

Differentially Expressed Genes Regulating Glutathione Metabolism, Protein-Folding, and Unfolded Protein Response in Pancreatic β-Cells in Type 2 Diabetes Mellitus.

Impaired redox homeostasis in the endoplasmic reticulum (ER) may contribute to proinsulin misfolding and thus to activate the unfolded protein response (UPR) and apoptotic pathways, culminating in pancreatic β-cell loss and type 2 diabetes (T2D). The present study was designed to identify differentially expressed genes (DEGs) encoding enzymes for glutathione metabolism and their impact on the expression levels of genes regulating protein folding and UPR in β-cells of T2D patients. The GEO transcriptome datasets of β-cells of diabetics and non-diabetics, GSE20966 and GSE81608, were analyzed for 142 genes of interest using limma and GREIN software, respectively. Diabetic β-cells showed dataset-specific patterns of DEGs (FDR ≤ 0.05) implicated in the regulation of glutathione metabolism (ANPEP, PGD, IDH2, and CTH), protein-folding (HSP90AB1, HSP90AA1, HSPA1B, HSPA8, BAG3, NDC1, NUP160, RLN1, and RPS19BP1), and unfolded protein response (CREB3L4, ERP27, and BID). The GCLC gene, encoding the catalytic subunit of glutamate-cysteine ligase, the first rate-limiting enzyme of glutathione biosynthesis, was moderately down-regulated in diabetic β-cells from both datasets (p ≤ 0.05). Regression analysis established that genes involved in the de novo synthesis of glutathione, GCLC, GCLM, and GSS affect the expression levels of genes encoding molecular chaperones and those involved in the UPR pathway. This study showed for the first time that diabetic β-cells exhibit alterations in the expression of genes regulating glutathione metabolism, protein-folding, and UPR and provided evidence for the molecular crosstalk between impaired redox homeostasis and abnormal protein folding, underlying ER stress in type 2 diabetes.

Endoplasmic reticulum stress and mitochondrial dysfunction during aging: Role of sphingolipids

The endoplasmic reticulum (ER) plays a key role in the regulation of protein folding, lipid synthesis, calcium homeostasis, and serves as a primary site of sphingolipid biosynthesis. ER stress (ER dysfunction) participates in the development of mitochondrial dysfunction during aging. Mitochondria are in close contact with the ER through shared mitochondria associated membranes (MAM). Alteration of sphingolipids contributes to mitochondria-driven cell injury. Cardiolipin is a phospholipid that is critical to maintain enzyme activity in the electron transport chain. The aim of the current study was to characterize the changes in sphingolipids and cardiolipin in ER, MAM, and mitochondria during the progression of aging in young (3 mo.), middle (18 mo.), and aged (24 mo.) C57Bl/6 mouse hearts. ER stress increased in hearts from 18 mo. mice and mice exhibited mitochondrial dysfunction by 24 mo. Hearts were pooled to isolate ER, MAM, and subsarcolemmal mitochondria (SSM). LC-MS/MS quantification of lipid content showed that aging increased ceramide content in ER and MAM. In addition, the contents of sphingomyelin and monohexosylceramides are also increased in the ER from aged mice. Aging increased the total cardiolipin content in the ER. Aging did not alter the total cardiolipin content in mitochondria or MAM yet altered the composition of cardiolipin with aging in line with increased oxidative stress compared to young mice. These results indicate that alteration of sphingolipids can contribute to the ER stress and mitochondrial dysfunction that occurs during aging.

Viral Evolution Shaped by Host Proteostasis Networks.

Understanding the factors that shape viral evolution is critical for developing effective antiviral strategies, accurately predicting viral evolution, and preventing pandemics. One fundamental determinant of viral evolution is the interplay between viral protein biophysics and the host machineries that regulate protein folding and quality control. Most adaptive mutations in viruses are biophysically deleterious, resulting in a viral protein product with folding defects. In cells, protein folding is assisted by a dynamic system of chaperones and quality control processes known as the proteostasis network. Host proteostasis networks can determine the fates of viral proteins with biophysical defects, either by assisting with folding or by targeting them for degradation. In this review, we discuss and analyze new discoveries revealing that host proteostasis factors can profoundly shape the sequence space accessible to evolving viral proteins. We also discuss the many opportunities for research progress proffered by the proteostasis perspective on viral evolution and adaptation.

Alpha 2-macroglobulin acts as a clearance factor in the lysosomal degradation of extracellular misfolded proteins

Proteostasis regulates protein folding and degradation; its maintenance is essential for resistance to stress and aging. The loss of proteostasis is associated with many age-related diseases. Within the cell, molecular chaperones facilitate the refolding of misfolded proteins into their bioactive forms, thus preventing undesirable interactions and aggregation. Although the mechanisms of intracellular protein degradation pathways for intracellular misfolded proteins have been extensively studied, the protein degradation pathway for extracellular proteins remain poorly understood. In this study, we identified several misfolded proteins that are substrates for alpha 2-macroglobulin (α2M), an extracellular chaperone. We also established a lysosomal internalization assay for α2M, which revealed that α2M mediates the lysosomal degradation of extracellular misfolded proteins. Comparative analyses of α2M and clusterin, another extracellular chaperone, indicated that α2M preferentially targets aggregation-prone proteins. Thus, we present the degradation pathway of α2M, which interacts with aggregation-prone proteins for lysosomal degradation via selective internalization.

Porcine salivary proteome analysis identifies potential early pregnancy-specific protein biomarkers

Early diagnosis of pregnancy is of utmost importance to optimize profit in pig husbandry. Identifying candidate protein biomarkers for early diagnosis of pregnancy in a non-invasive sample such as saliva may produce a colossallead to accomplish the purpose. Therefore, in this study, comparative salivary proteome profile of day 12 of gestation, representing elongation of blastocysts stage and non-pregnant sows was explored by label-free quantitation (LFQ) based mass spectrometry approach to identify early pregnancy biomarkers. A total of 115 proteins were identified as differentially expressed proteins (DEPs) with significant difference between non-pregnant and early pregnancy groups. Among the DEPs, majority of the proteins (82 out of 115 DEPs) were found to be down-regulated in early pregnancy group (fold change >2) compared to non-pregnant control. Functional classification and pathway analysis of the DEPs revealed involvement of most of the proteins in integrin signalling pathways, blood coagulation, carbohydrate metabolism, oxidative stress response and regulation of protein folding. Few DEPs with higher fold change during early pregnancy such as thioredoxin, heat shock 70 kDa protein 1A, alpha 1-S haptoglobin, and glutathione S-transferase pi 1 may have potential as biomarkers for early pregnancy diagnosis in pigs based on their recognized role in different pregnancy related activities. Overall, our results provide a set of salivary proteins which can be used as potential biomarkers for early pregnancy diagnosis after large scale validation.