Role Of Chaperones Research Articles

Substoichiometric Hsp104 regulates the genesis and persistence of self-replicable amyloid seeds of Sup35 prion domain

Prion-like self-perpetuating conformational conversion of proteins is involved in both transmissible neurodegenerative diseases in mammals and non-Mendelian inheritance in yeast. The transmissibility of amyloid-like aggregates is dependent on the stoichiometry of chaperones such as heat shock proteins (Hsps), including disaggregases. To provide the mechanistic underpinnings of the formation and persistence of prefibrillar amyloid seeds, we investigated the role of substoichiometric Hsp104 on the in vitro amyloid aggregation of the prion domain (NM-domain) of Saccharomyces cerevisiae Sup35. At low substoichiometric concentrations, we show Hsp104 exhibits a dual role: it considerably accelerates the formation of prefibrillar species by shortening the lag phase but also prolongs their persistence by introducing unusual kinetic halts and delaying their conversion into mature amyloid fibers. Additionally, Hsp104-modulated amyloid species displayed a better seeding capability compared to NM-only amyloids. Using biochemical and biophysical tools coupled with site-specific dynamic readouts, we characterized the distinct structural and dynamical signatures of these amyloids. We reveal that Hsp104-remodeled amyloidogenic species are compositionally diverse in prefibrillar aggregates and are packed in a more ordered fashion compared to NM-only amyloids. Finally, we show these Hsp104-remodeled, conformationally distinct NM aggregates display an enhanced autocatalytic self-templating ability that might be crucial for phenotypic outcomes. Taken together, our results demonstrate that substoichiometric Hsp104 promotes compositional diversity and conformational modulations during amyloid formation, yielding effective prefibrillar seeds that are capable of driving prion-like Sup35 propagation. Our findings underscore the key functional and pathological roles of substoichiometric chaperones in prion-like propagation.

Direct Observation of the Mechanical Role of Bacterial Chaperones in Protein Folding

Protein folding under force is an integral source of generating mechanical energy in various cellular processes, ranging from protein translation to degradation. Although chaperones are well known to interact with proteins under mechanical force, how they respond to force and control cellular energetics remains unknown. To address this question, we introduce a real-time magnetic tweezer technology herein to mimic the physiological force environment on client proteins, keeping the chaperones unperturbed. We studied two structurally distinct client proteins--protein L and talin with seven different chaperones─independently and in combination and proposed a novel mechanical activity of chaperones. We found that chaperones behave differently, while these client proteins are under force, than their previously known functions. For instance, tunnel-associated chaperones (DsbA and trigger factor), otherwise working as holdase without force, assist folding under force. This process generates an additional mechanical energy up to ∼147 zJ to facilitate translation or translocation. However, well-known cytoplasmic foldase chaperones (PDI, thioredoxin, or DnaKJE) do not possess the mechanical folding ability under force. Notably, the transferring chaperones (DnaK, DnaJ, and SecB) act as holdase and slow down the folding process, both in the presence and absence of force, to prevent misfolding of the client proteins. This provides an emerging insight of mechanical roles of chaperones: they can generate or consume energy by shifting the energy landscape of the client proteins toward a folded or an unfolded state, suggesting an evolutionary mechanism to minimize energy consumption in various biological processes.

Telemedicine and Plastic Surgery: Principles from the American Society of Plastic Surgeons Health Policy Committee.

In the wake of the recent coronavirus disease of 2019 public health emergency, care delivery by means of telemedicine using audiovisual virtual platforms has become an important tool for patient communication. There are many logistic, medicolegal, and practical aspects of telemedicine that should be considered by the practicing plastic surgeon. Successful virtual patient interactions require an understanding of medical licensure requirements to perform telemedicine visits in a certain region. In addition, it is imperative to be familiar with specific liability and malpractice concerns, in addition to Health Insurance Portability and Accountability Act regulations before conducting electronic visits. During consultations, providers should be aware of proper physician conduct and the potential role of chaperones. Furthermore, appropriate visit documentation, in addition to telemedicine billing and coding, has to be ensured. Lastly, plastic surgeons should adhere to the rules of controlled substance prescription by means of telemedicine platforms. This article describes these salient topics surrounding telemedicine visits that are faced by plastic surgeons and discusses strategies to optimize and ensure safe use of virtual platforms.

HSc70 interactome reveal major role of macroautophagy and minor role of chaperone mediated autophagy in K-Ras G12V cell proliferation and survival

Constitutively active K-Ras oncogene mutation at G12V changes the proteome of cells and activates macroautophagy for cell advantage. Inhibition of macroautophagy impairs K-Ras mediated tumor progression to a limited extent with increase of spontaneous tumors due to poorly understood mechanisms. Here, we show that inhibition of macroautophagy in K-Ras G12V mouse embryonic fibroblasts (MEFs) hyper activates chaperon mediated autophagy (CMA). Quantitative identification of CMA substrates through co-immunoprecipitation of CMA component heat shock cognate 70 (Hsc70) demonstrates a shift of proteins from macroautophagy to CMA mediated degradation. However, macroautophagy impairment show significant inhibition on proliferation and CMA hyper activation provides a basal support to macroautophagy-inhibited MEFs for survival. On the other hand, K-Ras G12V MEFs impaired of CMA reduces number of Hsc70 clients but activated macroautophagy significantly compensated CMA loss. Nonetheless, co-inhibition of CMA and macroautophagy had a synergistic detrimental effect on both proliferation and survival of MEFs expressing K-Ras G12V mutant. Our results point to K-Ras G12V MEFs dependency on macroautophagy and CMA partly compensates its loss for survival but not hyper-proliferation; implicating that targeting both macroautophagy and CMA as a promising therapeutic target in G12V mutation associated K-Ras cancers. SignificanceThe present study provides a framework of Hsc70 interacting proteins, which differentially interact with Hsc70 in response to autophagy alterations. The role of proteins accumulation and induced proteo-toxicity could be underlying factor in macroautophagy and CMA co-inhibited K-Ras G12V MEFs phenotype. Our study provides rational for adaptive mechanisms in K-Ras tumors inhibited with different autophagy pathways and also supports targeting both macroautophagy and CMA simultaneously as therapeutic target. At the same time current study will help in characterizing the underlying cellular processes that may play a role in escaping tutor suppressor role CMA and macroautophagy in cancers harboring K-Ras G12V mutation that may be further utilized to identify molecular targets for K-Ras-driven cancers.

A Yeast Model System to Study the Human Orthologs of the Ribosome‐Associated Complex

Prions are a class of misfolded proteins that form protein aggregates that are infectious and can self‐propagate, causing human diseases like Creutzfeldt‐Jakob. Additionally, many other diseases are known to involve protein misfolding and formation of amyloid aggregates as a characteristic of their pathology. To suppress the formation of misfolded proteins, cells have evolved various quality control systems, including chaperone proteins that can help protect nascent polypeptide chains from misfolding. Saccharomyces cerevisiae, also known as brewer’s yeast, has been used as a model organism to study protein misfolding and prion formation, including the yeast [PSI+] prion formed by the misfolding of the translation termination factor Sup35. The ribosome‐associated complex (RAC) is a chaperone complex composed of two subcomponents, in yeast called Zuo1 and Ssz1. Previous work from our lab and others has shown that the presence of the RAC on ribosomes decreases the frequency of the formation of the [PSI+] prion and reduces the toxicity of aggregation‐prone polypeptides. The human ortholog of yeast RAC is composed of Mpp11 and Hsp70L1. Previous studies have shown that human RAC can rescue the growth defect associated with deletion of the yeast RAC components. We therefore hypothesized that the function of the RAC complex, including its ability to suppress prion formation and toxicity of aggregation‐prone proteins, may be conserved from yeast to humans. We transformed yeast lacking the RAC components Zuo1 and Ssz1 with plasmids expressing the human orthologs of these chaperones. Growth assays confirmed previous studies showing that the human RAC components partially restore growth to yeast lacking endogenous RAC. In addition, like the yeast counterparts, human RAC reduces the formation of the [PSI+] prion. This result highlights the potential of the yeast model system to investigate the roles of human chaperones in modulating protein folding and misfolding. To further investigate the potential of this yeast model system, we have studied the ability of the human RAC components to counter the toxicity of several human disease‐associated proteins expressed in yeast, including those with polyQ repeats, the amyloid‐β peptide, and □‐synuclein, which are associated with Huntington’s, Alzheimer’s, and Parkinson’s Diseases in humans, respectively. The results provide insights on the use of S. cerevisiaein studying human diseases involving protein misfolding.

Role of HSP90 Family Molecular Chaperone in Regulating Chloroplast Protein Homeostasis and Plant Development in Arabidopsis

Chloroplasts carry out photosynthesis in plants and provide most food sources for living organisms. Either divided or differentiated from proplastids and etioplasts, the biogenesis of thylakoid membranes is the hallmark of chloroplast maturation and functionality, and this process requires a large set of photosynthetic proteins that must be synthesized on cytosolic ribosomes and then imported into the chloroplast stroma. Thylakoid lumen proteins travel further through the stroma and then cross the thylakoid membrane through one of the ancestral translocases. Like the cytosolic environment and the other major organelles, a cohort of molecular chaperones and proteases reside within the chloroplast to ensure proper protein homeostasis. We have identified and confirmed the interaction between the essential plastid HSP90 family heat shock protein HSP90C and a thylakoid lumen located photosystem II subunit PsbO1. To understand the biological significance of the interaction, we adopted transgenic approaches, specific HSP90 inhibitors, biochemical and in organello protein transport assays to study how the HSP90 family protein facilitates the representative lumen proteins transport across the thylakoid membrane. Specifically, we showed that the expression of the molecular chaperone is developmentally regulated, and its expression is highly correlated with some photosynthetic proteins while not with the others. Additionally, we demonstrated that HSP90C physically interacts with the thylakoid SEC translocon subunit, and that its chaperone activity is required for efficient PsbO1 transport. We also investigated the signature sequences of different HSP90 subfamily proteins and provided evidence that the chloroplast located HSP90C contains features specialized for some photosynthetic proteins interaction, and thus the chloroplast maturation and functionality.

A Comprehensive Stemness Gene Expression Analysis Signifies the Role of ABC Transporters and Molecular Chaperons in Determining the Fate of Human Neural Precursor Cells

The major aim of this study was to identify the most common stemness genes across different stem cell types and further validate them in human fetal subventricular zone-derived primary and cultured neural precursor cells (NPCs). This study involved the use of a unique method of stemness meta-analysis (SMA) for investigating comprehensive upregulation and downregulation of differentially expressed genes (DEGs) among different stem cell populations. A total of 55 mouse and human data sets targeting crucial genes identified in seven different types of stem cells population were screened and subjected to independent DEGs analysis using SMA. Identified 30 meta-gene signatures were subjected to functional enrichment analysis based on their biological processes and molecular functions. Validation of enriched meta-gene signatures was performed using RT-qPCR. Cellular localization of ABCB1 and ABCG2 was identified using immunofluorescence staining, whereas functional assessment was performed using western-blot. SMA analysis revealed that among 52 commonly expressed genes, 30 genes were either upregulated or downregulated in at least two stem cell populations. Further gene enrichment analysis showed nine genes (ABCB1, ABCG2, HSPA4, HSPA9, HSPA14, Nestin, Sox-2, Oct-4, and Notch-2) with the highest combined scores among 30 meta-gene signatures. RT-qPCR demonstrated that all the enriched gene signatures were significantly upregulated in primary NPCs and further downregulated during NPCs lineage differentiation in culture except HSPA4, HSPA9, and HSPA14 gene transcripts. The stemness meta-gene signatures were abundantly expressed in human NPCs population which categorically suggest the involvement of these genes/pathways in pluripotency maintenance and molecular switches for lineage differentiation while HSP-70 had a neuroprotective effect.

Adaptive responses of marine diatoms to zinc scarcity and ecological implications

Scarce dissolved surface ocean concentrations of the essential algal micronutrient zinc suggest that Zn may influence the growth of phytoplankton such as diatoms, which are major contributors to marine primary productivity. However, the specific mechanisms by which diatoms acclimate to Zn deficiency are poorly understood. Using global proteomic analysis, we identified two proteins (ZCRP-A/B, Zn/Co Responsive Protein A/B) among four diatom species that became abundant under Zn/Co limitation. Characterization using reverse genetic techniques and homology data suggests putative Zn/Co chaperone and membrane-bound transport complex component roles for ZCRP-A (a COG0523 domain protein) and ZCRP-B, respectively. Metaproteomic detection of ZCRPs along a Pacific Ocean transect revealed increased abundances at the surface (<200 m) where dZn and dCo were scarcest, implying Zn nutritional stress in marine algae is more prevalent than previously recognized. These results demonstrate multiple adaptive responses to Zn scarcity in marine diatoms that are deployed in low Zn regions of the Pacific Ocean.

Direct observation of chaperone-modulated talin mechanics with single-molecule resolution

Talin as a critical focal adhesion mechanosensor exhibits force-dependent folding dynamics and concurrent interactions. Being a cytoplasmic protein, talin also might interact with several cytosolic chaperones; however, the roles of chaperones in talin mechanics remain elusive. To address this question, we investigated the force response of a mechanically stable talin domain with a set of well-known unfoldase (DnaJ, DnaK) and foldase (DnaKJE, DsbA) chaperones, using single-molecule magnetic tweezers. Our findings demonstrate that chaperones could affect adhesion proteins’ stability by changing their folding mechanics; while unfoldases reduce their unfolding force from ~11 pN to ~6 pN, foldase shifts it upto ~15 pN. Since talin is mechanically synced within 2 pN force ranges, these changes are significant in cellular conditions. Furthermore, we determined that chaperones directly reshape the energy landscape of talin: unfoldases decrease the unfolding barrier height from 26.8 to 21.7 kBT, while foldases increase it to 33.5 kBT. We reconciled our observations with eukaryotic Hsp70 and Hsp40 and observed their similar function of decreasing the talin unfolding barrier. Quantitative mapping of this chaperone-induced talin folding landscape directly illustrates that chaperones perturb the adhesion protein stability under physiological force, thereby, influencing their force-dependent interactions and adhesion dynamics.

Regulation by Different Types of Chaperones of Amyloid Transformation of Proteins Involved in the Development of Neurodegenerative Diseases.

The review highlights various aspects of the influence of chaperones on amyloid proteins associated with the development of neurodegenerative diseases and includes studies conducted in our laboratory. Different sections of the article are devoted to the role of chaperones in the pathological transformation of alpha-synuclein and the prion protein. Information about the interaction of the chaperonins GroE and TRiC as well as polymer-based artificial chaperones with amyloidogenic proteins is summarized. Particular attention is paid to the effect of blocking chaperones by misfolded and amyloidogenic proteins. It was noted that the accumulation of functionally inactive chaperones blocked by misfolded proteins might cause the formation of amyloid aggregates and prevent the disassembly of fibrillar structures. Moreover, the blocking of chaperones by various forms of amyloid proteins might lead to pathological changes in the vital activity of cells due to the impaired folding of newly synthesized proteins and their subsequent processing. The final section of the article discusses both the little data on the role of gut microbiota in the propagation of synucleinopathies and prion diseases and the possible involvement of the bacterial chaperone GroE in these processes.

Proximity proteomics of C9orf72 dipeptide repeat proteins identifies molecular chaperones as modifiers of poly-GA aggregation

The most common inherited cause of two genetically and clinico-pathologically overlapping neurodegenerative diseases, amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), is the presence of expanded GGGGCC intronic hexanucleotide repeats in the C9orf72 gene. Aside from haploinsufficiency and toxic RNA foci, another non-exclusive disease mechanism is the non-canonical translation of the repeat RNA into five different dipeptide repeat proteins (DPRs), which form neuronal inclusions in affected patient brains. While evidence from cellular and animal models supports a toxic gain-of-function of pathologic poly-GA, poly-GR, and poly-PR aggregates in promoting deposition of TDP-43 pathology and neurodegeneration in affected brain areas, the relative contribution of DPRs to the disease process in c9FTD/ALS patients remains unclear. Here we have used the proximity-dependent biotin identification (BioID) proximity proteomics approach to investigate the formation and collective composition of DPR aggregates using cellular models. While interactomes of arginine rich poly-GR and poly-PR aggregates overlapped and were enriched for nucleolar and ribosomal proteins, poly-GA aggregates demonstrated a distinct association with proteasomal components, molecular chaperones (HSPA1A/HSP70, HSPA8/HSC70, VCP/p97), co-chaperones (BAG3, DNAJA1A) and other factors that regulate protein folding and degradation (SQSTM1/p62, CALR, CHIP/STUB1). Experiments in cellular models of poly-GA pathology show that molecular chaperones and co-chaperones are sequestered to the periphery of dense cytoplasmic aggregates, causing depletion from their typical cellular localization. Their involvement in the pathologic process is confirmed in autopsy brain tissue, where HSPA8, BAG3, VCP, and its adapter protein UBXN6 show a close association with poly-GA aggregates in the frontal cortex, temporal cortex, and hippocampus of c9FTLD and c9ALS cases. The association of heat shock proteins and co-chaperones with poly-GA led us to investigate their potential role in reducing its aggregation. We identified HSP40 co-chaperones of the DNAJB family as potent modifiers that increased the solubility of poly-GA, highlighting a possible novel therapeutic avenue and a central role of molecular chaperones in the pathogenesis of human C9orf72-linked diseases.

Understanding the role and mechanism of fact histone chaperone through single-molecule fluorescence imaging

Modifications of histones in eukaryotic cells cause reversible gene changes without alterations in the genetic code itself. Modified histones are distributed between the daughter DNA strands and serve as carriers of epigenetic memory. Histone chaperones are involved in remodeling the nucleosome during transcription and replication, and our recent genetic experiments indicate that chaperones are involved in epigenetic maintenance. In particular, we found that deleting Pob3, one of the essential protein subunits of the Facilitates Chromatin Transcription (FACT) histone chaperone, suppresses epigenetic inheritance.

Copper in the tumor microenvironment and tumor metastasis.

Copper (Cu), an essential micronutrient, plays an essential role in several physiological processes, including cell proliferation and angiogenesis; however, its dysregulation induces oxidative stress and inflammatory responses. Significant Cu accumulation is observed in several tumor tissues. The bioavailability of intracellular Cu is tightly controlled by Cu transporters, including Cu transporter 1 (CTR1) and Cu-transporting P-type ATPase α and β (ATP7A and ATP7B), and Cu chaperones, including Cu chaperone for superoxide dismutase 1 (CCS) and antioxidant-1 (Atox-1). In several tumor tissues, these abnormalities that induce intra­cellular Cu accumulation are involved in tumor progression. In addition, functional disturbance in Cu-containing secretory enzymes, such as superoxide dismutase 3 (SOD3), and lysyl oxidase enzymes (LOX and LOXL1–4) with abnormal Cu dynamics plays a key role in tumor metastasis. For example, the loss of SOD3 in tumor tissues induces oxidative stress, which promotes neovascularization and epithelial-to-mesenchymal transition (EMT). LOX promotes collagen crosslinking, which functions in the metastatic niche formation. Accordingly, restricted Cu regulation may be a novel strategy for the inhibition of tumor metastasis. However, it is unclear how these Cu disturbances occur in tumor tissues and the exact molecular mechanisms underlying Cu secretory enzymes. In this review article, I discuss the role of Cu transporters, Cu chaperones, and Cu-containing secretory enzymes in tumor progression to better understand the role of Cu homeostasis in tumor tissues.

Revisiting the functions of periplasmic chaperones in the quality control of the autotransporter Ag43 using a phenotypically homogeneous Escherichia coli strain

Antigen 43 is a surface-displayed autotransporter protein that mediates bacterial self-association and pathogenicity. The quality control factors that facilitate Ag43 crossing the periplasm and inserting into the outer membrane remain enigmatic, mostly because Ag43 is phase variable and associated with heterologous phenotypes, which obscures the mutational effects of potential quality control factors. Here, we describe a screening method that allowed us to isolate a subpopulation of Escherichia coli that consistently displays an Ag43-mediated autoaggregation phenotype. Based on this subpopulation, we analyzed how disruptions of known periplasmic chaperones affect Ag43 biogenesis. We found that only the disruption of surA reduced Ag43 levels and abolished the autoaggregation phenotype of cells, but surA disruption did not affect the phase-variable expression of agn43. Using purified proteins, we showed that SurA effectively protected the β-barrel domain of Ag43 from aggregation. In contrast, the previously reported Ag43 biogenesis factor OsmY showed weak chaperoning effects on Ag43 only in the absence of SurA. Our results shed light on the roles of different periplasmic chaperones in Ag43 biogenesis and provide a methodology applicable to the study of other phase-variable proteins.

The sacrificial adaptor protein Skp functions to remove stalled substrates from the β-barrel assembly machine

The biogenesis of integral β-barrel outer membrane proteins (OMPs) in gram-negative bacteria requires transport by molecular chaperones across the aqueous periplasmic space. Owing in part to the extensive functional redundancy within the periplasmic chaperone network, specific roles for molecular chaperones in OMP quality control and assembly have remained largely elusive. Here, by deliberately perturbing the OMP assembly process through use of multiple folding-defective substrates, we have identified a role for the periplasmic chaperone Skp in ensuring efficient folding of OMPs by the β-barrel assembly machine (Bam) complex. We find that β-barrel substrates that fail to integrate into the membrane in a timely manner are removed from the Bam complex by Skp, thereby allowing for clearance of stalled Bam-OMP complexes. Following the displacement of OMPs from the assembly machinery, Skp subsequently serves as a sacrificial adaptor protein to directly facilitate the degradation of defective OMP substrates by the periplasmic protease DegP. We conclude that Skp acts to ensure efficient β-barrel folding by directly mediating the displacement and degradation of assembly-compromised OMP substrates from the Bam complex.

New role of a histone chaperone, HirA: Involvement in kojic acid production associated with culture conditions in Aspergillusoryzae

Kojic acid (KA) is a representative secondary metabolite of Aspergillus oryzae, but the underlying molecular mechanisms that regulate KA production are unknown. This study tried to find a genetic factor of KA production in A.oryzae, with a special focus on liquid cultures. We screened a gene predicted to encode HirA, a subunit of the histone chaperon, the HIR complex. A gene disruption strain of hirA showed decreased KA production in liquid culture, whereas it showed increased KA production in plate culture. We confirmed that a decrease/increase of KA production observed by hirA disruption was caused by altered expression of kojA and kojR. These observations suggested the regulatory role of histone chaperon in secondary metabolism in filamentous fungi. So far as we know, this report is the first showing that disruption of a gene resulted in the opposite effect on KA production in liquid and plate cultures in A.oryzae.

Interactions between the Nucleoprotein and the Phosphoprotein of Pneumoviruses: Structural Insight for Rational Design of Antivirals.

Pneumoviruses include pathogenic human and animal viruses, the most known and studied being the human respiratory syncytial virus (hRSV) and the metapneumovirus (hMPV), which are the major cause of severe acute respiratory tract illness in young children worldwide, and main pathogens infecting elderly and immune-compromised people. The transcription and replication of these viruses take place in specific cytoplasmic inclusions called inclusion bodies (IBs). These activities depend on viral polymerase L, associated with its cofactor phosphoprotein P, for the recognition of the viral RNA genome encapsidated by the nucleoprotein N, forming the nucleocapsid (NC). The polymerase activities rely on diverse transient protein-protein interactions orchestrated by P playing the hub role. Among these interactions, P interacts with the NC to recruit L to the genome. The P protein also plays the role of chaperone to maintain the neosynthesized N monomeric and RNA-free (called N0) before specific encapsidation of the viral genome and antigenome. This review aims at giving an overview of recent structural information obtained for hRSV and hMPV P, N, and more specifically for P-NC and N0-P complexes that pave the way for the rational design of new antivirals against those viruses.

Investigating the non‐cell autonomous role of glial chaperones in Alzheimer’s disease

AbstractBackgroundAstrocytes are vital in the onset and progression of Alzheimer’s disease (AD). Accumulation of reactive astrocytes, together with tau phosphorylation, correlates very strongly with cognitive decline.Molecular chaperones are essential for maintaining protein homeostasis. One family of chaperones are the small heat shock proteins (sHSPs), which include HSPB1 and CRYAB. Expression of these sHSPs seems to be restricted to glial cells, and levels are found to increase in those astrocytes found in AD brains. The role that sHSP play in astrocytes in AD is still not known. Emerging evidence suggests vital interplay between different cell types during neurodegenerative diseases. We therefore aim to investigate the non‐cell autonomous role of astrocytic sHSPs in AD.MethodWe are using primary mouse neurons and organotypic brain slice cultures in conjunction with the recombinant adeno‐associated viral system (rAAV). These systems will allow us to replicate the tau pathology found in AD, investigate neuron‐astrocyte interactions and determine whether either can be altered by overexpression of our sHSPs.Using immunofluorescence, confocal microscopy and western blotting we are characterising expression and localization of sHSPs in post‐mortem human AD brain tissue and brain slice cultures.ResultOur data shows that HSPB1 is specifically expressed in astrocytes in both human brain tissue and slice cultures. Interestingly, HSPB1 levels in the human brain increase in GFAP‐positive astrocytes surrounding amyloid plaques. When organotypic brain slices are treated with cytokines or Aβ oligomers, reactive astrocytes are induced and levels of HSPB1 and CRYAB are also increased, similar to what we observe in human AD brain.ConclusionOur results in human AD brain highlight the importance of astrocytic HSPB1 in AD, and we provide evidence to suggest not only that organotypic brain slices are a good model to replicate and study the function of sHSPs in AD, but that HSPB1 and CRYAB play an important role in the response to AD‐relevant pathology.Using rAAVs, we aim to manipulate astrocytic sHSPs levels in organotypic brain slices to investigate whether astrocytic sHSPs could modulate neuronal health and tau pathology in a non‐cell autonomous manner.

Temporal specific coevolution of Hsp70 and co-chaperone stv expression in Drosophila melanogaster under selection for heat tolerance.

Heat shock proteins (Hsps) have long been candidates for ecological adaptation given their unequivocal role in mitigating cell damage from heat stress, but linking Hsps to heat tolerance has proven difficult given the complexity of thermal adaptation. Experimental evolution has been utilized to examine direct and correlated responses to selection for increased heat tolerance in Drosophila, often focusing on the major Hsp family Hsp70 and/or the master regulator HSF as a selection response, but rarely on other aspects of the heat shock complex. We examined Hsp70 and co-chaperone stv isoform transcript expression in Australian D. melanogaster lines selected for static heat tolerance, and observed a temporal and stv isoform specific, coordinated transcriptional selection response with Hsp70, suggesting that increased chaperone output accompanied increased heat tolerance. We hypothesize that the coordinated evolutionary response of Hsp70 and stv may have arisen as a correlated response resulting from a shared regulatory hierarchy. Our work highlights the complexity and specificity of the heat shock response in D. melanogaster. The selected lines examined also showed correlated responses for other measures of heat tolerance, and the coevolution of Hsp70 and stv provide new avenues to examine the common mechanisms underpinning direct and correlated phenotypic responses to selection for heat tolerance.

Molecular Mechanisms of Hypertensive Nephropathy: Renoprotective Effect of Losartan through Hsp70.

Hypertensive nephrosclerosis is the second most common cause of end-stage renal disease after diabetes. For years, hypertensive kidney disease has been focused on the afferent arterioles and glomeruli damage and the involvement of the renin angiotensin system (RAS). Nonetheless, in recent years, novel evidence has demonstrated that persistent high blood pressure injures tubular cells, leading to epithelial–mesenchymal transition (EMT) and tubulointerstitial fibrosis. Injury primarily determined at the glomerular level by hypertension causes changes in post-glomerular peritubular capillaries that in turn induce endothelial damage and hypoxia. Microvasculature dysfunction, by inducing hypoxic environment, triggers inflammation, EMT with epithelial cells dedifferentiation and fibrosis. Hypertensive kidney disease also includes podocyte effacement and loss, leading to disruption of the filtration barrier. This review highlights the molecular mechanisms and histologic aspects involved in the pathophysiology of hypertensive kidney disease incorporating knowledge about EMT and tubulointerstitial fibrosis. The role of the Hsp70 chaperone on the angiotensin II–induced EMT after angiotensin II type 1 receptor (AT1R) blockage, as a possible molecular target for therapeutic strategy against hypertensive renal damage is discussed.