Heat shock protein 60 is a high-affinity high-density lipoprotein binding protein

Synergistic Anti-Inflammatory Activity of Apolipoprotein A-I and CIGB-258 in Reconstituted High-Density Lipoproteins (rHDL) against Acute Toxicity of Carboxymethyllysine in Zebrafish and Its Embryo

CIGB-258 is a 3 kDa altered peptide ligand from heat shock protein (HSP) 60 that exhibits anti-inflammatory activity against the acute toxicity of carboxymethyllysine (CML) with antioxidant and anti-glycation activities via protection of high-density lipoprotein (HDL) and apolipoprotein A-I (apoA-I). It is necessary to test a synergistic interaction between apoA-I and CIGB-258 in reconstituted high-density lipoproteins (rHDL). Several rHDLs were synthesized containing palmitoyloleoyl phosphatidylcholine (POPC), cholesterol, apoA-I, and CIGB-258 at molar ratios of 95:5:1:0, 95:5:1:0.1, 95:5:1:0.5, and 95:5:1:1 for rHDL-(1:0), rHDL-(1:0.1), rHDL-(1:0.5), and rHDL-(1:1), respectively. As the CIGB-258 content in rHDL was increased, the particle size of rHDL was 1.4-times higher than rHDL-(1:0) to rHDL-(1:1), from 60 nm to 83 nm, respectively. As the CIGB-258 content was increased, the rHDL showed the most resistance to isothermal denaturation by a urea treatment, and rHDL-(1:1) exhibited the highest structural stability and the strongest antioxidant ability against LDL oxidation. Co-treatment of rHDL-(1:0), rHDL-(1:0.5), and rHDL-(1:1) resulted in up to 10%, 24%, and 34% inhibition of HDL glycation, inhibition of HDL glycation, which was caused by the CML, with protection of apoA-I. Microinjection of each rHDL into zebrafish embryos in the presence of CML showed that a higher CIGB-258 content in rHDL was associated with higher survivability with the least inflammation and apoptosis. Furthermore, an intraperitoneal injection of rHDL and CML showed that a higher CIGB-258 content in rHDL was also associated with higher survivability of zebrafish and faster recovery of swimming ability. The rHDL-(1:1) group showed the lowest triglyceride, AST, and ALT serum levels with the least production of interleukin-6, oxidized product, and neutrophil infiltration in hepatic tissue. In conclusion, CIGB-258 could bind well to phospholipids and cholesterol to stabilize apoA-I in the rHDL structure against denaturation stress and larger particle sizes. The rHDL containing CIGB-258 enhanced the in vitro antioxidant ability against LDL oxidation, the anti-glycation activity to protect HDL, and the in vivo anti-inflammatory activity against CML toxicity in zebrafish adults and embryos. Overall, incorporating apoA-I and CIGB-258 in rHDL resulted in a synergistic interaction to enhance the structural and functional correlations in a dose-dependent manner of CIGB-258.

Anti-Inflammatory Activity of CIGB-258 against Acute Toxicity of Carboxymethyllysine in Paralyzed Zebrafish via Enhancement of High-Density Lipoproteins Stability and Functionality

Background: Hyperinflammation is frequently associated with the chronic pain of autoimmune disease and the acute death of coronavirus disease (COVID-19) via a severe cytokine cascade. CIGB-258 (Jusvinza®), an altered peptide ligand with 3 kDa from heat shock protein 60 (HSP60), inhibits the systemic inflammation and cytokine storm, but the precise mechanism is still unknown. Objective: The protective effect of CIGB-258 against inflammatory stress of N-ε-carboxymethyllysine (CML) was tested to provide mechanistic insight. Methods: CIGB-258 was treated to high-density lipoproteins (HDL) and injected into zebrafish and its embryo to test a putative anti-inflammatory activity under presence of CML. Results: Treatment of CML (final 200 μM) caused remarkable glycation of HDL with severe aggregation of HDL particles to produce dysfunctional HDL, which is associated with a decrease in apolipoprotein A-I stability and lowered paraoxonase activity. Degradation of HDL3 by ferrous ions was attenuated by a co-treatment with CIGB-258 with a red-shift of the Trp fluorescence in HDL. A microinjection of CML (500 ng) into zebrafish embryos resulted in the highest embryo death rate, only 18% of survivability with developmental defects. However, co-injection of CIGB-258 (final 1 ng) caused the remarkable elevation of survivability around 58%, as well as normal developmental speed. An intraperitoneal injection of CML (final 250 μg) into adult zebrafish resulted acute paralysis, sudden death, and laying down on the bottom of the cage with no swimming ability via neurotoxicity and inflammation. However, a co-injection of CIGB-258 (1 μg) resulted in faster recovery of the swimming ability and higher survivability than CML alone injection. The CML alone group showed 49% survivability, while the CIGB-258 group showed 97% survivability (p < 0.001) with a remarkable decrease in hepatic inflammation up to 50%. A comparison of efficacy with CIGB-258, Infliximab (Remsima®), and Tocilizumab (Actemra®) showed that the CIGB-258 group exhibited faster recovery and swimming ability with higher survivability than those of the Infliximab group. The CIGB-258 group and Tocilizumab group showed the highest survivability, the lowest plasma total cholesterol and triglyceride level, and the infiltration of inflammatory cells, such as neutrophils in hepatic tissue. Conclusion: CIGB-258 ameliorated the acute neurotoxicity, paralysis, hyperinflammation, and death induced by CML, resulting in higher survivability in zebrafish and its embryos by enhancing the HDL structure and functionality.

Homeostatic Roles of the Proteostasis Network in Dendrites

Cellular protein homeostasis, or proteostasis, is indispensable to the survival and function of all cells. Distinct from other cell types, neurons are long-lived, exhibiting architecturally complex and diverse multipolar projection morphologies that can span great distances. These properties present unique demands on proteostatic machinery to dynamically regulate the neuronal proteome in both space and time. Proteostasis is regulated by a distributed network of cellular processes, the proteostasis network (PN), which ensures precise control of protein synthesis, native conformational folding and maintenance, and protein turnover and degradation, collectively safeguarding proteome integrity both under homeostatic conditions and in the contexts of cellular stress, aging, and disease. Dendrites are equipped with distributed cellular machinery for protein synthesis and turnover, including dendritically trafficked ribosomes, chaperones, and autophagosomes. The PN can be subdivided into an adaptive network of three major functional pathways that synergistically govern protein quality control through the action of (1) protein synthesis machinery; (2) maintenance mechanisms including molecular chaperones involved in protein folding; and (3) degradative pathways (e.g., Ubiquitin-Proteasome System (UPS), endolysosomal pathway, and autophagy. Perturbations in any of the three arms of proteostasis can have dramatic effects on neurons, especially on their dendrites, which require tightly controlled homeostasis for proper development and maintenance. Moreover, the critical importance of the PN as a cell surveillance system against protein dyshomeostasis has been highlighted by extensive work demonstrating that the aggregation and/or failure to clear aggregated proteins figures centrally in many neurological disorders. While these studies demonstrate the relevance of derangements in proteostasis to human neurological disease, here we mainly review recent literature on homeostatic developmental roles the PN machinery plays in the establishment, maintenance, and plasticity of stable and dynamic dendritic arbors. Beyond basic housekeeping functions, we consider roles of PN machinery in protein quality control mechanisms linked to dendritic plasticity (e.g., dendritic spine remodeling during LTP); cell-type specificity; dendritic morphogenesis; and dendritic pruning.

Protein moonlighting: what is it, and why is it important?

Members of the GroEL/HSP60 protein family have been studied for many years because of their critical roles as ATP-dependent molecular chaperones, so it might come as a surprise that some have important functions in ATP-poor conditions, for example, when secreted outside the cell. At least some members of each of the HSP10, HSP70, HSP90, HSP100 and HSP110 heat shock protein families are also 'moonlighting proteins'. Moonlighting proteins exhibit more than one physiologically relevant biochemical or biophysical function within one polypeptide chain. In this class of multifunctional proteins, the multiple functions are not due to gene fusions or multiple proteolytic fragments. Several hundred moonlighting proteins have been identified, and they include a diverse set of proteins with a large variety of functions. Some participate in multiple biochemical processes by using an active site pocket for catalysis and a different part of the protein's surface to interact with other proteins. Moonlighting proteins play a central role in many diseases, and the development of novel treatments would be aided by more information addressing current questions, for example, how some are targeted to multiple cellular locations and how a single function can be targeted by therapeutics without targeting a function not involved in disease.This article is part of the theme issue 'Heat shock proteins as modulators and therapeutic targets of chronic disease: an integrated perspective'.

Mitochondria chaperone GRP75 moonlighting as a cell cycle controller to derail endocytosis provides an opportunity for nanomicrosphere intracellular delivery

Understanding how cancer cells regulate endocytosis during the cell cycle could lead us to capitalize this event pharmacologically. Although certain endocytosis pathways are attenuated during mitosis, the endocytosis shift and regulation during the cell cycle have not been well clarified. The conventional concept of glucose-regulated proteins (GRPs) as protein folding chaperones was updated by discoveries that translocated GRPs assume moonlighting functions that modify the immune response, regulate viral release, and control intracellular trafficking. In this study, GRP75, a mitochondria matrix chaperone, was discovered to be highly expressed in mitotic cancer cells. Using synchronized cell models and the GRP75 gene knockdown and ectopic overexpression strategy, we showed that: (1) clathrin-mediated endocytosis (CME) was inhibited whereas clathrin-independent endocytosis (CIE) was unchanged or even up-regulated in the cell cycle M-phase; (2) GRP75 inhibited CME but promoted CIE in the M-phase, which is largely due to its high expression in cancer cell mitochondria; (3) GRP75 targeting by its small molecular inhibitor MKT-077 enhanced cell cycle G1 phase-privileged CME, which provides an opportunity for intracellular delivery of nanomicrospheres sized from 40 nm to 100 nm. Together, our results revealed that GRP75 moonlights as a cell cycle controller and endocytosis regulator in cancer cells, and thus has potential as a novel interference target for nanoparticle drugs delivery into dormant cancer cells.

Physical Features of Intracellular Proteins that Moonlight on the Cell Surface

Moonlighting proteins comprise a subset of multifunctional proteins that perform two or more biochemical functions that are not due to gene fusions, multiple splice variants, proteolytic fragments, or promiscuous enzyme activities. The project described herein focuses on a sub-set of moonlighting proteins that have a canonical biochemical function inside the cell and perform a second biochemical function on the cell surface in at least one species. The goal of this project is to consider the biophysical features of these moonlighting proteins to determine whether they have shared characteristics or defining features that might suggest why these particular proteins were adopted for a second function on the cell surface, or if these proteins resemble typical intracellular proteins. The latter might suggest that many other normally intracellular proteins found on the cell surface might also be moonlighting in this fashion. We have identified 30 types of proteins that have different functions inside the cell and on the cell surface. Some of these proteins are found to moonlight on the surface of multiple species, sometimes with different extracellular functions in different species, so there are a total of 98 proteins in the study set. Although a variety of intracellular proteins (enzymes, chaperones, etc.) are observed to be re-used on the cell surface, for the most part, these proteins were found to have physical characteristics typical of intracellular proteins. Many other intracellular proteins have also been found on the surface of bacterial pathogens and other organisms in proteomics experiments. It is quite possible that many of those proteins also have a moonlighting function on the cell surface. The increasing number and variety of known moonlighting proteins suggest that there may be more moonlighting proteins than previously thought, and moonlighting might be a common feature of many more proteins.

Calcium-dependent mitochondrial extrusion in ciliated protozoa

Here we demonstrate that ciliated protozoa can jettison mitochondria as intact organelles, releasing their contents to the extracellular space either in a soluble form, or in association with membrane vesicles at the cell periphery. The response is triggered by lateral clustering of GPI-anchored surface antigens, or by heat shock. In the first instance, extrusion is accompanied by elevated levels of intracellular calcium and is inhibited by Verapamil and BAPTA-AM arguing strongly for the involvement of calcium in triggering the response. Cells survive mitochondrial discharge raising the interesting possibility that extrusion is an early evolutionary adaptation to cell stress.

Listeria monocytogenes uses Listeria adhesion protein (LAP) to promote bacterial transepithelial translocation and induces expression of LAP receptor Hsp60

Listeria monocytogenes interaction with the intestinal epithelium is a key step in the infection process. We demonstrated that Listeria adhesion protein (LAP) promotes adhesion to intestinal epithelial cells and facilitates extraintestinal dissemination in vivo. The LAP receptor is a stress response protein, Hsp60, but the precise role for the LAP-Hsp60 interaction during Listeria infection is unknown. Here we investigated the influence of physiological stressors and Listeria infection on host Hsp60 expression and LAP-mediated bacterial adhesion, invasion, and transepithelial translocation in an enterocyte-like Caco-2 cell model. Stressors such as heat (41°C), tumor necrosis factor alpha (TNF-α) (100 U), and L. monocytogenes infection (10(4) to 10(6) CFU/ml) significantly (P < 0.05) increased plasma membrane and intracellular Hsp60 levels in Caco-2 cells and consequently enhanced LAP-mediated L. monocytogenes adhesion but not invasion of Caco-2 cells. In transepithelial translocation experiments, the wild type (WT) exhibited 2.7-fold more translocation through Caco-2 monolayers than a lap mutant, suggesting that LAP is involved in transepithelial translocation, potentially via a paracellular route. Short hairpin RNA (shRNA) suppression of Hsp60 in Caco-2 cells reduced WT adhesion and translocation 4.5- and 3-fold, respectively, while adhesion remained unchanged for the lap mutant. Conversely, overexpression of Hsp60 in Caco-2 cells enhanced WT adhesion and transepithelial translocation, but not those of the lap mutant. Furthermore, initial infection with a low dosage (10(6) CFU/ml) of L. monocytogenes increased plasma membrane and intracellular expression of Hsp60 significantly, which rendered Caco-2 cells more susceptible to subsequent LAP-mediated adhesion and translocation. These data provide insight into the role of LAP as a virulence factor during intestinal epithelial infection and pose new questions regarding the dynamics between the host stress response and pathogen infection.

Identification of plasma membrane autoantigens in autoimmune hepatitis type 1 using a proteomics tool

Autoimmune hepatitis (AIH) is a liver disease with circulating autoantibodies predominantly directed against widely held cellular components. Because AIH is a liver-specific disease, autoantibodies against plasma membrane antigens may be involved in its pathogenesis and have been reported; however, no definite identification has been described. We thus investigated the fine specificity of anti-hepatocyte plasma membrane autoantibodies in type 1 AIH (AIH-1) using a proteomic tool. A plasma membrane-enriched fraction was validated using enzymatic activity and western blot analysis experiments. Sera from AIH-1 patients (n = 65) and from 90 controls, that is, healthy blood donors (n = 40) and patients with systemic diseases (n = 20) or other liver diseases (n = 30), were studied by immunoblot performed with plasma membrane proteins resolved by either sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) or 2-dimensional (2D) electrophoresis. Proteins contained in the immunoreactive spots were identified by sequences provided by ion-trap mass spectrometry. Hepatocytes probed with sera were also studied using confocal immunofluorescence and immunoelectron microscopy. The more prominent bands stained by patient sera were located at 38 kDa, 48, 50, 52 kDa, 62 kDa, 70 kDa, and a 95-kDa double band. Six proteins with known potential plasma membrane expression were identified: liver arginase (38 kDa), cytokeratins (CK) 8 and 18 (48-52 kDa), heat shock proteins (HSP) of 60, 70, 90 kDa, and valosin-containing protein (VCP) of 92 kDa. The presence of anti-membrane antibodies was confirmed by immunofluorescence and immunoelectron microscopy.

CONCLUSION

Overall, our data demonstrate that liver arginase, CK 8/18, HSP 60, HSP 70, HSP 90, and VCP represent potential candidate targets on liver membrane for autoantibodies in AIH-1.

On the brotherhood of the mitochondrial chaperones mortalin and heat shock protein 60

The heat shock chaperones mortalin/mitochondrial heat shock protein 70 (mtHsp70) and Hsp60 are found in multiple subcellular sites and function in the folding and intracellular trafficking of many proteins. The chaperoning activity of these 2 proteins involves different structural and functional mechanisms. In spite of providing an excellent model for an evolutionarily conserved molecular "brotherhood", their individual functions, although overlapping, are nonredundant. As they travel to various locations, both chaperones acquire different binding partners and exert a more divergent involvement in tumorigenesis, cellular senescence, and immunology. An understanding of their functional biology may lead to novel designing and development of therapeutic strategies for cancer and aging.

Frequency-specific association of antibodies against heat shock proteins 60 and 70 with noise-induced hearing loss in Chinese workers

Noise exposure may result in production of auto-antibodies against heat shock proteins (Hsps), which might be of significance in the pathogenesis or prognosis (or both) of auto-immune ear diseases. However, it is not known whether these antibodies are associated with noise-induced hearing loss (NIHL) in workers exposed to noise in occupational settings. Using immunoblotting with human recombinant Hsps, audiological assessment, and multivariate logistic regression models, we investigated the presence of antibodies against Hsp60 and Hsp70 and hearing levels, and analyzed their associations with NIHL in 399 workers exposed to noise between 75 and 115 dB. Our findings showed that the prevalence of positive anti-Hsp70 was significantly higher in the workers with slight and moderate high-frequency hearing loss than in normal workers (P < 0.05). Furthermore, the prevalence of positive anti-Hsp60 in workers with moderate low-frequency NIHL was significantly higher than in the normal (P < 0.01). The levels of anti-Hsp70 and anti-Hsp60 seemed correlated, and the level of anti-Hsp70 better predicted the level of anti-Hsp60. An elevated plasma level of anti-Hsp70 was associated with a nonsignificantly increased risk of high-frequency NIHL (adjusted OR = 1.45; 95% CI = 0.89-2.36) and an elevated plasma level of anti-Hsp60 was associated with a nonsignificantly increased risk of the low-frequency NIHL (adjusted OR = 2.25; 95% CI = 0.85-5.96). These results suggest that the production of anti-Hsp60 and anti-Hsp70 may play a role in the pathogenesis of NIHL, and that anti-Hsps may be a risk factor. The precise mechanisms for the elevation of antibodies against Hsps caused by noise exposure and their possible role in the development of NIHL warrant further investigations.

Heat shock protein 60 acts as a receptor for the Listeria adhesion protein in Caco-2 cells

The 104-kDa Listeria adhesion protein (LAP) in Listeria monocytogenes is involved in binding to various mammalian cell lines. However, the receptor that interacts with LAP in eukaryotic cells is unknown. In this study, scanning immunoelectron microscopy qualitatively demonstrated greater binding capacity of wild-type (WT) L. monocytogenes strain (F4244) than a LAP-deficient mutant strain (KB208) to Caco-2 cells. The goal of this study was identification of the host cell receptor for LAP. Using a Western blot ligand overlay assay, we identified a protein of 58 kDa to be the putative receptor for LAP from Caco-2 cells. N-terminal sequencing and subsequent database search identified this protein as heat shock protein 60 (Hsp60). Modified immunoseparation with protein A-Sepharose beads bound to the LAP-specific monoclonal antibody H7 (MAb-H7) and a sequential incubation with LAP preparation and Caco-2 lysate confirmed the receptor to be the same 58-kDa protein. Western blot analysis with anti-Hsp60 MAb of whole-cell adhesion between Caco-2 and WT also revealed the receptor protein to be a 58-kDa protein, thus corroborating the identification of Hsp60 as a host cell receptor for LAP. Furthermore, the anti-Hsp60 antibody also caused approximately 74% reduction in binding of L. monocytogenes WT to Caco-2 cells, whereas a control antibody, C11E9, had no effect on binding. The adhesion mechanism of L. monocytogenes to eukaryotic cells is a complex process, and identification of Hsp60 as a receptor for LAP adds to the list of previously discovered ligand-receptor modules that are essential to achieve successful adhesion.

Interaction of antibodies against cytomegalovirus with heat-shock protein 60 in pathogenesis of atherosclerosis

BACKGROUND

Infections and autoimmunity have been implicated in the pathogenesis of atherosclerosis. Cytomegalovirus has been shown to contribute to the disease. Autoantibodies against human heat-shock protein (HSP) 60 are present in most atherosclerotic patients, and their titre correlates with disease severity, suggesting that anti-HSP60 might be implicated in disease pathogenesis. We postulated that cytomegalovirus infection might induce antibodies able to bind human HSP60 and to cause endothelial-cell damage.

METHODS

We studied 180 patients with coronary-artery disease, raised high sensitivity C-reactive protein concentrations, and presence or absence of traditional risk factors; 90 patients with coronary-artery disease, normal values for high sensitivity C-reactive protein, and no traditional risk factors; and 98 controls. Individual sera were used to define the relevant epitope of HSP60 by ELISA. Affinity purified IgGs were used to identify endothelial cell-surface ligands by western blot and to induce apoptotic cell death.

FINDINGS

We identified an 11 aminoacid sequence of HSP60 that was recognised by most patients with coronary-artery disease. This peptide shares homology with cytomegalovirus-derived proteins UL122 and US28. The same patients' sera recognised UL122-derived and US28-derived peptides. Purified IgGs against HSP60 and the viral peptides bound non-stressed human endothelial cells and induced endothelial-cell apoptosis by interaction with cell-surface molecules.

INTERPRETATION

During cytomegalovirus infection, antibodies against the virus can arise that are able to crossreact with human HSP60 and cause apoptosis of non-stressed endothelial cells, which is judged a primary event in the pathogenesis of atherosclerosis.

Chaperonin 60 unfolds its secrets of cellular communication

The cell biology of the chaperonins (Cpns) has been intensively studied over the past 25 years. These ubiquitous and essential molecules assist proteins to fold into their native state and function to protect proteins from denaturation after stress. The structure of the most widely studied Cpn60, Escherichia coli GroEL, has been solved and its mechanism of protein folding action largely established. But in the last decade, evidence has accumulated to suggest that the Cpn60s have functions in addition to intracellular protein folding, particularly the ability to act as intercellular signals with a wide variety of biological effects. Cpn60 has the ability to stimulate cells to produce proinflammatory cytokines and other proteins involved in immunity and inflammation and may, therefore, provide a link between innate and adaptive immunity. Cpn60s are also thought to be pathogenic factors in a wide range of diseases and have recently been reported to be present in the circulation of normal subjects and those with heart disease. An interesting facet of these proteins is the finding that in spite of significant sequence conservation, individual Cpn60 proteins can express very different biological activities. This review discusses the work to date, which has revealed the cell-cell signaling actions of Cpn60 proteins.

Human heat shock protein 60 (409-424) fragment is recognized by serum antibodies of patients with acute coronary syndromes

Acute coronary syndromes (ACS), including unstable angina (UA) and acute myocardial infarction (MI), are clinical manifestations of a progressive atherosclerotic process. Antibodies (Ab) to heat shock proteins (hsp) have been reported to be associated with atherosclerosis. Blood samples from 35 patients with ACS and 20 healthy volunteers were tested for Ab to human hsp60 by an enzyme-linked immunosorbent assay (ELISA). Levels of specific serum Ab against hsp60 were significantly elevated in patients with ACS when compared to clinically healthy subjects. To determine the antigenic determinants recognized by these Ab, antibody binding to seven peptides, selected from the hydrophilic and acrophilic regions of the human hsp60 molecule, was assessed. Despite the individual variation in the immune response among patients, one immunodominant region was revealed corresponding to the hsp60 (409-424) peptide. The identification of this epitope may be important for understanding the function of this protein in the atherosclerotic process.