Heat shock protein Hspa13 regulates endoplasmic reticulum and cytosolic proteostasis through modulation of protein translocation

Identification and characterization of hsp70 gene family in Acrossocheilus fasciatus based on genome and full-length transcripts

Global warming and temperature extremes are increasingly recognized as critical environmental stressors for aquatic species, particularly stream fish, which are becoming more vulnerable due to fluctuating water temperatures and a scarcity of thermal refuges. The hsp70 gene family plays a crucial role in maintaining cellular homeostasis and mediating stress responses, especially under thermal stress. However, the evolutionary dynamics and functional diversity of this gene family remain relatively unexplored in stream fish. In this study, we investigated the hsp70 gene family in Acrossocheilus fasciatus, an economically important stream fish, by integrating full-length transcriptome data with genomic. Through the use of genomic and full-length transcriptome sequencing, we refined the genome annotation of A. fasciatus and identified 18 hsp70 family members, including six novel genes previously unannotated in the genome. Phylogenetic, domain, and motif analyses revealed significant structural variation among these genes. Chromosomal localization demonstrated their distribution across multiple chromosomes, while synteny analysis confirmed evolutionary conservation with A. fasciatus, Danio rerio and Onychostoma macrolepis. RNA-seq and qRT-PCR analyses revealed that hsp70 genes showed minimal differential expression in brain tissue under acute thermal stress and in muscle tissue under chronic thermal stress. qRT-PCR analysis revealed significant differential expression of hsp70 genes in muscle tissue under acute thermal stress, with hspa8b, hspa13, and hyou1 exhibited marked upregulation, whereas hspa14 was significantly downregulated. These genes could serve as potential biomarkers. The integration of full-length transcriptome data with genomic information improved the precision of gene identification and genome annotation. These findings carry significant and far-reaching implications for advancing our comprehension of thermal stress in aquatic organisms, potentially informing and enhancing conservation and breeding initiatives.

Dysregulation of N-glycosylation by Rpn1 knockout in spermatocytes induces male infertility via endoplasmic reticulum stress in mice

N-glycosylation protein modification plays a crucial regulatory role in numerous biological processes, although their contribution to male reproduction in mammals remains largely undefined. Here, we found that Ribophorin I (RPN1), a subunit of oligosaccharyltransferase complex, is indispensable for spermatogenesis in male germ cells. Germ cell-specific Rpn1 knockout results in significant inhibition of the progression of meiosis, consequently disrupting homologous chromosome pairing, meiotic recombination, and DNA double strand breaks repair during meiosis. N-glycoproteomic profiling revealed that glycosylation levels are reduced in endoplasmic reticulum-associated proteins, while functional analyses showed that Rpn1 deficiency could inhibit endoplasmic reticulum function and trigger endoplasmic reticulum stress during meiosis and increasing apoptosis levels in mice. These findings highlight the essential physiological functions of N-glycosylation modification in male spermatogenesis and expand our understanding of its role in male fertility.

Hspa13 Deficiency Impaired Marginal Zone B Cells Regulatory Function and Contributed to Lupus Pathogenesis

Dysregulated IL-10 producing regulatory B cells (Bregs) are associated with the progression of systemic lupus erythematosus. An immunomodulatory role of heat shock proteins (HSPs) is implicated in autoimmune diseases. However, the molecular basis underlying the role of Hspa13 in regulating Bregs function and lupus pathogenesis remains unclear. In this study, Bregs display higher Hspa13 expression than IL-10- B cells. Induction of IL-10 production is weakened in B cells with Hspa13 knockdown or knockout. Hspa13 binds to the IL-10 promoter via the TATA or CAAT box and activates IL-10 transcription in the nucleus. Furthermore, Hspa13 positive cells are enriched in marginal zone (MZ) B cells to regulate IL-10 production. Stimulated B220+ B or MZ B cells from CD19creHspa13fl/fl mice for Breg induction show an impaired capacity to promote CD4+Foxp3+ regulatory T cells (Treg) differentiation. In lupus MRL/lpr mice, a decline in Treg differentiation is accompanied by decreased Hspa13 expression in both Bregs and MZ B cells. Moreover, adoptive transfusion of Bregs and MZ B cells from CD19creHspa13fl/fl mice fails to increase the frequency of Tregs, attenuate renal pathology, or decrease anti-dsDNA antibody levels. These results explain the unique role of Hspa13 in determining MZ regulatory function and affecting lupus pathogenesis.

Sodium alginate and bovine serum albumin co-combined improved the cryopreservation quality of boar sperm through the PI3K-AKT pathway

Context The occurrence of apoptosis due to transient oxidative damage to spermatozoa presents a significant challenge in semen preservation. At present, the addition of protective agents is the primary method for mitigating this damage and involves the addition of protective agents. Aims This study aims to elucidate the mechanism of action of cryopreservation and to identify high-quality combinatorial cryopreservation dilutions. Methods In this study, two protective agents, bovine serum albumin (BSA) and sodium alginate (SA), were combined to evaluate the effectiveness of these novel additives in protecting porcine sperm from damage during cryopreservation. The mechanism of action of the SA and BSA combination was further elucidated at the molecular level, with key proteins being identified through proteomic analysis. Key results The findings indicated that sperm treated with 2mg/mL SA and 5mg/mL BSA exhibited optimal motility parameters, superior functional integrity and the most effective ability to alleviate oxidative stress. Combined with proteomic data, the results suggested that these additives regulate improvements in sperm quality by mediating the activity of the PI3K-AKT pathway. Conclusions This study found that the combination of SA and BSA provides an effective protective effect for frozen sperm preservation. Implications The findings offer theoretical and technical support for the use of composite additive to protect sperm from damage, which is crucial for enhancing the quality of pig semen and improving reproductive outcomes.

Caenorhabditis elegans inositol hexaphosphate pathways couple to RNA interference and pathogen defense

RNA interference (RNAi) is an evolutionarily conserved pathway that defends against viral infections in diverse organisms. Caenorhabditis elegans mutations that enhance RNAi have revealed pathways that may regulate antiviral defense. A genetic screen for C. elegans mutations that fail to up-regulate a defense response reporter transgene detected mutations that enhance RNAi to silence this reporter gene in the inositol polyphosphate multikinase impk-1, the synMuv B gene lin-15B, and the pathogen defense response gene pals-22. Using other assays for enhanced RNAi, we found that the impk-1 alleles and an ippk-1 gene inactivation of a later step in inositol hexaphosphate (IP6) synthesis, and the lin-15B and pals-22 alleles enhance RNAi. IP6 has been known for decades to bind and stabilize human adenosine deaminase that acts on RNA (ADAR) as well as the paralog tRNA editing ADAT. We show that the C. elegans IP6 pathway is also required for mRNA and tRNA editing. Thus, a deficiency in two axes of RNA editing enhances the already potent C. elegans RNAi antiviral defense, suggesting adenosine to inosine RNA editing may normally moderate this siRNA antiviral defense pathway. The C. elegans IP6-deficient mutants are synthetic lethal with a set of enhanced RNAi mutants that act in the polyploid hypodermis to regulate collagen secretion and signaling from that tissue, implicating IP6 signaling especially in this tissue. This enhanced antiviral RNAi response uses the C. elegans RIG-I-like receptor DRH-1 to activate the unfolded protein response (UPR). The production of primary siRNAs, rather than secondary siRNAs, contributes to this activation of the UPR through XBP-1 signaling. The gon-14 and pal-17 mutants that also emerged from this screen act in the mitochondrial defense pathway rather than by enhancing RNAi.

Knockdown of HSPA13 Inhibits TGFβ1-Induced Epithelial-Mesenchymal Transition of RPE by Suppressing the PI3K/Akt Signaling Pathway

PURPOSE

This study aimed to explore the impact of HSPA13 on epithelial-mesenchymal transition (EMT) in retinal pigment epithelial (RPE) cells and proliferative vitreoretinopathy (PVR) development, along with its associated molecular mechanisms.

METHODS

HSPA13 expression was evaluated in epiretinal membranes (ERMs) from patients with PVR using immunohistochemistry. The effects of HSPA13 knockdown on TGFβ1-induced EMT in hESC-RPE cells were studied through quantitative PCR (qPCR), Western blot, and wound healing assays. Intracellular Ca2+ levels were measured using Fluo-8/AM incubation. A rat PVR model was induced by the intravitreal injection of RPE cells combined with platelet-rich plasma (PRP). RNA-seq was applied to study the molecular mechanism of HSPA13 knockdown-mediated EMT inhibition.

RESULTS

HSPA13 was found in human ERMs and its expression increased with TGFβ1 treatment in hESC-RPE cells. Knockdown of HSPA13 inhibited TGFβ1-induced EMT and migration. In the PVR rat model, HSPA13 was expressed in the ERMs and its knockdown in RPE cells reduced the development of PVR. Consistent with these observations, RNA-seq showed a global suppression of TGFβ1-induced EMT and migration by shHSPA13 in RPE cells. Mechanistically, TGFβ1 treatment increased intracellular Ca2+ levels, leading to an upregulation of HSPA13 expression. Downregulation of HSPA13 hindered the phosphorylation of PI3K/Akt in TGFβ1-induced RPE cells.

CONCLUSIONS

Our study revealed the involvement of HSPA13 in PVR development, as well as in TGFβ1-induced EMT of RPE through the PI3K/Akt signaling pathway. Targeting HSPA13-related pathways involved in regulating EMT in RPE cells could serve as a novel therapeutic approach for patients with PVR.

Comparative analysis of SEC61A1 mutant R236C in two patient-derived cellular platforms

SEC61A1 encodes a central protein of the mammalian translocon and dysfunction results in severe disease. Recently, mutation R236C was identified in patients having autosomal dominant polycystic liver disease (ADPLD). The molecular phenotype of R236C was assessed in two cellular platforms. Cells were immortalized by retroviral transduction of an oncogene (UCi) or reprogrammed to induced pluripotent stem cells (iPSC) that were differentiated to cholangiocyte progenitor-like cells (CPLC). UCi and CPLC were subjected to analyses of molecular pathways that were associated with development of disease. UCi displayed markers of epithelial cells, while CPLCs expressed typical markers of both cholangiocytes and hepatocytes. Cells encoding R236C showed a stable, continuous proliferation in both platforms, however growth rates were reduced as compared to wildtype control. Autophagy, cAMP synthesis, and secretion of important marker proteins were reduced in R236C-expressing cells. In addition, R236C induced increased calcium leakiness from the ER to the cytoplasm. Upon oxidative stress, R236C led to a high induction of apoptosis and necrosis. Although the grade of aberrant cellular functions differed between the two platforms, the molecular phenotype of R236C was shared suggesting that the mutation, regardless of the cell type, has a dominant impact on disease-associated pathways.

Quantitative Measurement of Transthyretin Mistargeting by Proximity Labeling and Parallel Reaction Monitoring

Proximity labeling is a powerful approach for characterizing subcellular proteomes. We recently demonstrated that proximity labeling can be used to identify mistrafficking of secretory proteins, such as occurs during pre-emptive quality control (pre-QC) following endoplasmic reticulum (ER) stress. This assay depends on protein quantification by immunoblotting and densitometry, which sometimes suffers from poor sensitivity. Here, we integrate parallel reaction monitoring (PRM) mass spectrometry to enable a more quantitative platform, and assess how chemical ER stressors impact pre-QC of the model secretory protein transthyretin in HEK293T cells. We find that some drug treatments affect labeling efficiency, which can be controlled for by normalizing to APEX2 auto-labeling. While some chemical ER stress inducers including Brefeldin A and thapsigargin induce pre-QC, tunicamycin and dithiothreitol do not, indicating ER stress alone is not sufficient. This finding contrasts with the canonical model of pre-QC induction, and establishes the utility of our platform.

Closest horizons of Hsp70 engagement to manage neurodegeneration

Our review seeks to elucidate the current state-of-the-art in studies of 70-kilodalton-weighed heat shock proteins (Hsp70) in neurodegenerative diseases (NDs). The family has already been shown to play a crucial role in pathological aggregation for a wide spectrum of brain pathologies. However, a slender boundary between a big body of fundamental data and its implementation has only recently been crossed. Currently, we are witnessing an anticipated advancement in the domain with dozens of studies published every month. In this review, we briefly summarize scattered results regarding the role of Hsp70 in the most common NDs including Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS). We also bridge translational studies and clinical trials to portray the output for medical practice. Available options to regulate Hsp70 activity in NDs are outlined, too.

Quantitative Measurement of Secretory Protein Mistargeting by Proximity Labeling and Parallel Reaction Monitoring

Proximity labeling is a powerful approach for characterizing subcellular proteomes. We recently demonstrated that proximity labeling can be used to identify mistrafficking of secretory proteins, such as occurs during pre-emptive quality control (pre-QC) following endoplasmic reticulum (ER) stress. This assay depends on protein quantification by immunoblotting and densitometry, which is only semi-quantitative and suffers from poor sensitivity. Here, we integrate parallel reaction monitoring mass spectrometry to enable a more quantitative platform for ER import. PRM as opposed to densitometry improves quantification of transthyretin mistargeting while also achieving at least a ten-fold gain in sensitivity. The multiplexing of PRM also enabled us to evaluate a series of normalization approaches, revealing that normalization to auto-labeled APEX2 peroxidase is necessary to account for drug treatment-dependent changes in labeling efficiency. We apply this approach to systematically characterize the relationship between chemical ER stressors and ER pre-QC induction in HEK293T cells. Using dual-FLAG-tagged transthyretin (FLAGTTR) as a model secretory protein, we find that Brefeldin A treatment as well as ER calcium depletion cause pre-QC, while tunicamycin and dithiothreitol do not, indicating ER stress alone is not sufficient. This finding contrasts with the canonical model of pre-QC induction, and establishes the utility of our platform.

Is It Still Possible to Think about HSP70 as a Therapeutic Target in Onco-Hematological Diseases?

The search for molecules to be targeted that are involved in apoptosis resistance/increased survival and pathogenesis of onco-hematological malignancies is ongoing since these diseases are still not completely understood. Over the years, a good candidate has been identified in the Heat Shock Protein of 70kDa (HSP70), a molecule defined as “the most cytoprotective protein ever been described”. HSP70 is induced in response to a wide variety of physiological and environmental insults, allowing cells to survive lethal conditions. This molecular chaperone has been detected and studied in almost all the onco-hematological diseases and is also correlated to poor prognosis and resistance to therapy. In this review, we give an overview of the discoveries that have led us to consider HSP70 as a therapeutic target for mono- or combination-therapies in acute and chronic leukemias, multiple myeloma and different types of lymphomas. In this excursus, we will also consider HSP70 partners, such as its transcription factor HSF1 or its co-chaperones whose druggability could indirectly affect HSP70. Finally, we will try to answer the question asked in the title of this review considering that, despite the effort made by research in this field, HSP70 inhibitors never reached the clinic.