Characterization of obesity-related diseases and inflammation using single cell immunophenotyping in two different diet-induced obesity models.

BACKGROUND: Obesity is a growing problem worldwide and a major risk factor for many chronic diseases. The accumulation of adipose tissue leads to the release of significant amounts of pro-inflammatory cytokines and adipokines, resulting in a low-grade systemic inflammation. However, the mechanisms behind the development of obesity-related diseases are not fully understood. Therefore, our study aimed to investigate the pathological changes and inflammatory processes at systemic level and in individual organs in two different diet-induced mouse obesity models. METHODS: Male C57BL6/J mice were fed by high-fat diet (HFD), high-fat/high-fructose diet (HFD + FR) or normal chow for 21 weeks starting at 3 months of age (n = 15 animals/group). Insulin resistance was tested by oral glucose tolerance test. Pathological changes were investigated on hematoxylin-eosin-stained liver and brown adipose tissue sections. The gene expression levels of adipokines and cytokines were analyzed by qPCR in adipose tissues, whereas serum protein concentrations were determined by multiplex immunoassays. Immunophenotyping of isolated blood, bone marrow and spleen cells was performed by single-cell mass cytometry. RESULTS: Weight gain, glucose intolerance and hepatic steatosis were more severe in the HFD + FR group than in the control and HFD groups. This was accompanied by a higher level of systemic inflammation, as indicated by increased expression of pro-inflammatory genes in visceral white adipose tissue and by a higher serum TNFα level. In addition, immunophenotyping revealed the increase of the surface expressions of CD44 and CD69 on various cell types, such as CD8+ and CD4 + T-cells, B-cells and macrophages, in animals with obesity. CONCLUSIONS: The combination of HFD with fructose supplementation promotes more properly the symptoms of metabolic syndrome. Therefore, the combined high-fat/high-fructose nutrition can be a more suitable model of the Western diet. However, despite these differences, both models showed immunophenotypic changes that may be associated with increased risk of obesity-related cancer.

Mild Hyperthermia-Induced Thermogenesis in the Endoplasmic Reticulum Defines Stress Response Mechanisms.

Previous studies reported that a mild, non-protein-denaturing, fever-like temperature increase induced the unfolded protein response (UPR) in mammalian cells. Our dSTORM super-resolution microscopy experiments revealed that the master regulator of the UPR, the IRE1 (inositol-requiring enzyme 1) protein, is clustered as a result of UPR activation in a human osteosarcoma cell line (U2OS) upon mild heat stress. Using ER thermo yellow, a temperature-sensitive fluorescent probe targeted to the endoplasmic reticulum (ER), we detected significant intracellular thermogenesis in mouse embryonic fibroblast (MEF) cells. Temperatures reached at least 8 °C higher than the external environment (40 °C), resulting in exceptionally high ER temperatures similar to those previously described for mitochondria. Mild heat-induced thermogenesis in the ER of MEF cells was likely due to the uncoupling of the Ca2+/ATPase (SERCA) pump. The high ER temperatures initiated a pronounced cytosolic heat-shock response in MEF cells, which was significantly lower in U2OS cells in which both the ER thermogenesis and SERCA pump uncoupling were absent. Our results suggest that depending on intrinsic cellular properties, mild hyperthermia-induced intracellular thermogenesis defines the cellular response mechanism and determines the outcome of hyperthermic stress.

Emerging Lipid Targets in Glioblastoma.

GBM accounts for most of the fatal brain cancer cases, making it one of the deadliest tumor types. GBM is characterized by severe progression and poor prognosis with a short survival upon conventional chemo- and radiotherapy. In order to improve therapeutic efficiency, considerable efforts have been made to target various features of GBM. One of the targetable features of GBM is the rewired lipid metabolism that contributes to the tumor's aggressive growth and penetration into the surrounding brain tissue. Lipid reprogramming allows GBM to acquire survival, proliferation, and invasion benefits as well as supportive modulation of the tumor microenvironment. Several attempts have been made to find novel therapeutic approaches by exploiting the lipid metabolic reprogramming in GBM. In recent studies, various components of de novo lipogenesis, fatty acid oxidation, lipid uptake, and prostaglandin synthesis have been considered promising targets in GBM. Emerging data also suggest a significant role hence therapeutic potential of the endocannabinoid metabolic pathway in GBM. Here we review the lipid-related GBM characteristics in detail and highlight specific targets with their potential therapeutic use in novel antitumor approaches.

The Crystal Structure of the Hsp90-LA1011 Complex and the Mechanism by Which LA1011 May Improve the Prognosis of Alzheimer's Disease.

Functional changes in chaperone systems play a major role in the decline of cognition and contribute to neurological pathologies, such as Alzheimer's disease (AD). While such a decline may occur naturally with age or with stress or trauma, the mechanisms involved have remained elusive. The current models suggest that amyloid-ß (Aß) plaque formation leads to the hyperphosphorylation of tau by a Hsp90-dependent process that triggers tau neurofibrillary tangle formation and neurotoxicity. Several co-chaperones of Hsp90 can influence the phosphorylation of tau, including FKBP51, FKBP52 and PP5. In particular, elevated levels of FKBP51 occur with age and stress and are further elevated in AD. Recently, the dihydropyridine LA1011 was shown to reduce tau pathology and amyloid plaque formation in transgenic AD mice, probably through its interaction with Hsp90, although the precise mode of action is currently unknown. Here, we present a co-crystal structure of LA1011 in complex with a fragment of Hsp90. We show that LA1011 can disrupt the binding of FKBP51, which might help to rebalance the Hsp90-FKBP51 chaperone machinery and provide a favourable prognosis towards AD. However, without direct evidence, we cannot completely rule out effects on other Hsp90-co-chaprone complexes and the mechanisms they are involved in, including effects on Hsp90 client proteins. Nonetheless, it is highly significant that LA1011 showed promise in our previous AD mouse models, as AD is generally a disease affecting older patients, where slowing of disease progression could result in AD no longer being life limiting. The clinical value of LA1011 and its possible derivatives thereof remains to be seen.

Development of a Laser Microdissection-Coupled Quantitative Shotgun Lipidomic Method to Uncover Spatial Heterogeneity.

Lipid metabolic disturbances are associated with several diseases, such as type 2 diabetes or malignancy. In the last two decades, high-performance mass spectrometry-based lipidomics has emerged as a valuable tool in various fields of biology. However, the evaluation of macroscopic tissue homogenates leaves often undiscovered the differences arising from micron-scale heterogeneity. Therefore, in this work, we developed a novel laser microdissection-coupled shotgun lipidomic platform, which combines quantitative and broad-range lipidome analysis with reasonable spatial resolution. The multistep approach involves the preparation of successive cryosections from tissue samples, cross-referencing of native and stained images, laser microdissection of regions of interest, in situ lipid extraction, and quantitative shotgun lipidomics. We used mouse liver and kidney as well as a 2D cell culture model to validate the novel workflow in terms of extraction efficiency, reproducibility, and linearity of quantification. We established that the limit of dissectible sample area corresponds to about ten cells while maintaining good lipidome coverage. We demonstrate the performance of the method in recognizing tissue heterogeneity on the example of a mouse hippocampus. By providing topological mapping of lipid metabolism, the novel platform might help to uncover region-specific lipidomic alterations in complex samples, including tumors.

Remodeling of Liver and Plasma Lipidomes in Mice Lacking Cyclophilin D.

In recent years, several studies aimed to investigate the metabolic effects of non-functioning or absent cyclophilin D (CypD), a crucial regulatory component of mitochondrial permeability transition pores. It has been reported that the lack of CypD affects glucose and lipid metabolism. However, the findings are controversial regarding the metabolic pathways involved, and most reports describe the effect of a high-fat diet on metabolism. We performed a lipidomic analysis of plasma and liver samples of CypD-/- and wild-type (WT) mice to reveal the lipid-specific alterations resulting from the absence of CypD. In the CypD-/- mice compared to the WT animals, we found a significant change in 52% and 47% of the measured 225 and 201 lipid species in liver and plasma samples, respectively. The higher total lipid content detected in these tissues was not accompanied by abdominal fat accumulation assessed by nuclear magnetic resonance imaging. We also documented characteristic changes in the lipid composition of the liver and plasma as a result of CypD ablation with the relative increase in polyunsaturated membrane lipid species. In addition, we did not observe remarkable differences in the lipid distribution of hepatocytes using histochemistry, but we found characteristic changes in the hepatocyte ultrastructure in CypD-/- animals using electron microscopy. Our results highlight the possible long-term effects of CypD inhibition as a novel therapeutic consideration for various diseases.

Effect of HEAT therapy in patiEnts with type 2 Diabetes mellitus (HEATED): protocol for a randomised controlled trial.

INTRODUCTION: The burden of type 2 diabetes mellitus (T2DM) is increasing worldwide. Heat therapy has been found effective in improving glycaemic control. However, to date, there is a lack of randomised controlled studies investigating the efficacy of heat therapy in T2DM. Therefore, we aim to investigate whether heat therapy with natural thermal mineral water can improve glycaemic control in patients with T2DM. METHODS AND ANALYSIS: The HEAT therapy in patiEnts with type 2 Diabetes mellitus (HEATED) Study is a single-centre, two-arm randomised controlled trial being conducted at Harkány Thermal Rehabilitation Centre in Hungary. Patients with T2DM will be randomly assigned to group A (bath sessions in 38°C natural thermal mineral water) and group B (baths in thermoneutral water (30°C-32°C)). Both groups will complete a maximum of 5 weekly visits, averaging 50-60 visits over the 12-week study. Each session will last 30 min, with a physical check-up before the bath. At baseline, patients' T2DM status will be investigated thoroughly. Possible microvascular and macrovascular complications of T2DM will be assessed with physical and laboratory examinations. The short form-36 questionnaire will assess the quality of life. Patients will also be evaluated at weeks 4, 8 and 12. The primary endpoint will be the change of glycated haemoglobin from baseline to week 12. An estimated 65 patients will be enrolled per group, with a sample size re-estimation at the enrolment of 50% of the calculated sample size. ETHICS AND DISSEMINATION: The study has been approved by the Scientific and Research Ethics Committee of the Hungarian Medical Research Council (818-2/2022/EÜIG). Written informed consent is required from all participants. We will disseminate our results to the medical community and will publish our results in peer-reviewed journals. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov, NCT05237219.

The Small Heat Shock Protein, HSPB1, Interacts with and Modulates the Physical Structure of Membranes.

Small heat shock proteins (sHSPs) have been demonstrated to interact with lipids and modulate the physical state of membranes across species. Through these interactions, sHSPs contribute to the maintenance of membrane integrity. HSPB1 is a major sHSP in mammals, but its lipid interaction profile has so far been unexplored. In this study, we characterized the interaction between HSPB1 and phospholipids. HSPB1 not only associated with membranes via membrane-forming lipids, but also showed a strong affinity towards highly fluid membranes. It participated in the modulation of the physical properties of the interacting membranes by altering rotational and lateral lipid mobility. In addition, the in vivo expression of HSPB1 greatly affected the phase behavior of the plasma membrane under membrane fluidizing stress conditions. In light of our current findings, we propose a new function for HSPB1 as a membrane chaperone.

Distinct Cellular Tools of Mild Hyperthermia-Induced Acquired Stress Tolerance in Chinese Hamster Ovary Cells.

Mild stress could help cells to survive more severe environmental or pathophysiological conditions. In the current study, we investigated the cellular mechanisms which contribute to the development of stress tolerance upon a prolonged (0-12 h) fever-like (40 °C) or a moderate (42.5 °C) hyperthermia in mammalian Chinese Hamster Ovary (CHO) cells. Our results indicate that mild heat triggers a distinct, dose-dependent remodeling of the cellular lipidome followed by the expression of heat shock proteins only at higher heat dosages. A significant elevation in the relative concentration of saturated membrane lipid species and specific lysophosphatidylinositol and sphingolipid species suggests prompt membrane microdomain reorganization and an overall membrane rigidification in response to the fluidizing heat in a time-dependent manner. RNAseq experiments reveal that mild heat initiates endoplasmic reticulum stress-related signaling cascades resulting in lipid rearrangement and ultimately in an elevated resistance against membrane fluidization by benzyl alcohol. To protect cells against lethal, protein-denaturing high temperatures, the classical heat shock protein response was required. The different layers of stress response elicited by different heat dosages highlight the capability of cells to utilize multiple tools to gain resistance against or to survive lethal stress conditions.

Lipids and Trehalose Actively Cooperate in Heat Stress Management of Schizosaccharomyces pombe.

Homeostatic maintenance of the physicochemical properties of cellular membranes is essential for life. In yeast, trehalose accumulation and lipid remodeling enable rapid adaptation to perturbations, but their crosstalk was not investigated. Here we report about the first in-depth, mass spectrometry-based lipidomic analysis on heat-stressed Schizosaccharomyces pombe mutants which are unable to synthesize (tps1Δ) or degrade (ntp1Δ) trehalose. Our experiments provide data about the role of trehalose as a membrane protectant in heat stress. We show that under conditions of trehalose deficiency, heat stress induced a comprehensive, distinctively high-degree lipidome reshaping in which structural, signaling and storage lipids acted in concert. In the absence of trehalose, membrane lipid remodeling was more pronounced and increased with increasing stress dose. It could be characterized by decreasing unsaturation and increasing acyl chain length, and required de novo synthesis of stearic acid (18:0) and very long-chain fatty acids to serve membrane rigidification. In addition, we detected enhanced and sustained signaling lipid generation to ensure transient cell cycle arrest as well as more intense triglyceride synthesis to accommodate membrane lipid-derived oleic acid (18:1) and newly synthesized but unused fatty acids. We also demonstrate that these changes were able to partially substitute for the missing role of trehalose and conferred measurable stress tolerance to fission yeast cells.

Nicotinic Amidoxime Derivate BGP-15, Topical Dosage Formulation and Anti-Inflammatory Effect.

BGP-15 is a Hungarian-developed drug candidate with numerous beneficial effects. Its potential anti-inflammatory effect is a common assumption, but it has not been investigated in topical formulations yet. The aim of our study was to formulate 10% BGP-15 creams with different penetration enhancers to ensure good drug delivery, improve bioavailability of the drug and investigate the potential anti-inflammatory effect of BGP-15 creams in vivo. Since the exact mechanism of the effect is still unknown, the antioxidant effect (tested with UVB radiation) and the ability of BGP-15 to decrease macrophage activation were evaluated. Biocompatibility investigations were carried out on HaCaT cells to make sure that the formulations and the selected excipients can be safely used. Dosage form studies were also completed with texture analysis and in vitro release with Franz diffusion chamber apparatus. Our results show that the ointments were able to reduce the extent of local inflammation in mice, but the exact mechanism of the effect remains unknown since BGP-15 did not show any antioxidant effect, nor was it able to decrease LPS-induced macrophage activation. Our results support the hypothesis that BGP-15 has a potential anti-inflammatory effect, even if it is topically applied, but the mechanism of the effect remains unclear and requires further pharmacological studies.

Heat therapy shows benefit in patients with type 2 diabetes mellitus: a systematic review and meta-analysis.

AIMS: Type-2 diabetes mellitus (T2DM) is a common health condition which prevalence increases with age. Besides lifestyle modifications, passive heating could be a promising intervention to improve glycemic control. This study aimed to assess the efficacy of passive heat therapy on glycemic and cardiovascular parameters, and body weight among patients with T2DM. METHODS: A systematic review and meta-analysis were reported according to PRISMA Statement. We conducted a systematic search in three databases (MEDLINE, Embase, CENTRAL) from inception to 19 August 2021. We included interventional studies reporting on T2DM patients treated with heat therapy. The main outcomes were the changes in pre-and post-treatment cardiometabolic parameters (fasting plasma glucose, glycated plasma hemoglobin, and triglyceride). For these continuous variables, weighted mean differences (WMD) with 95% confidence intervals (CIs) were calculated. Study protocol number: CRD42020221500. RESULTS: Five studies were included in the qualitative and quantitative synthesis, respectively. The results showed a not significant difference in the hemoglobin A1c [WMD -0.549%, 95% CI (-1.262, 0.164), p = 0.131], fasting glucose [WMD -0.290 mmol/l, 95% CI (-0.903, 0.324), p = 0.355]. Triglyceride [WMD 0.035 mmol/l, 95% CI (-0.130, 0.200), p = 0.677] levels were comparable regarding the pre-, and post intervention values. CONCLUSION: Passive heating can be beneficial for patients with T2DM since the slight improvement in certain cardiometabolic parameters support that. However, further randomized controlled trials with longer intervention and follow-up periods are needed to confirm the beneficial effect of passive heat therapy.

Silencing of Poly(ADP-Ribose) Polymerase-2 Induces Mitochondrial Reactive Species Production and Mitochondrial Fragmentation.

PARP2 is a DNA repair protein. The deletion of PARP2 induces mitochondrial biogenesis and mitochondrial activity by increasing NAD+ levels and inducing SIRT1 activity. We show that the silencing of PARP2 causes mitochondrial fragmentation in myoblasts. We assessed multiple pathways that can lead to mitochondrial fragmentation and ruled out the involvement of mitophagy, the fusion-fission machinery, SIRT1, and mitochondrial unfolded protein response. Nevertheless, mitochondrial fragmentation was reversed by treatment with strong reductants, such as reduced glutathione (GSH), N-acetyl-cysteine (NAC), and a mitochondria-specific antioxidant MitoTEMPO. The effect of MitoTEMPO on mitochondrial morphology indicates the production of reactive oxygen species of mitochondrial origin. Elimination of reactive oxygen species reversed mitochondrial fragmentation in PARP2-silenced cells.

Male and Female Animals Respond Differently to High-Fat Diet and Regular Exercise Training in a Mouse Model of Hyperlipidemia.

Inappropriate nutrition and a sedentary lifestyle can lead to obesity, one of the most common risk factors for several chronic diseases. Although regular physical exercise is an efficient approach to improve cardiometabolic health, the exact cellular processes are still not fully understood. We aimed to analyze the morphological, gene expression, and lipidomic patterns in the liver and adipose tissues in response to regular exercise. Healthy (wild type on a normal diet) and hyperlipidemic, high-fat diet-fed (HFD-fed) apolipoprotein B-100 (APOB-100)-overexpressing mice were trained by treadmill running for 7 months. The serum concentrations of triglyceride and tumor necrosis factor α (TNFα), as well as the level of lipid accumulation in the liver, were significantly higher in HFD-fed APOB-100 males compared to females. However, regular exercise almost completely abolished lipid accumulation in the liver of hyperlipidemic animals. The expression level of the thermogenesis marker, uncoupling protein-1 (Ucp1), was significantly higher in the subcutaneous white adipose tissue of healthy females, as well as in the brown adipose tissue of HFD-fed APOB-100 females, compared to males. Lipidomic analyses revealed that hyperlipidemia essentially remodeled the lipidome of brown adipose tissue, affecting both the membrane and storage lipid fractions, which was partially restored by exercise in both sexes. Our results revealed more severe metabolic disturbances in HFD-fed APOB-100 males compared to females. However, exercise efficiently reduced the body weight, serum triglyceride levels, expression of pro-inflammatory factors, and hepatic lipid accumulation in our model.

Neuroinflammatory processes are augmented in mice overexpressing human heat-shock protein B1 following ethanol-induced brain injury.

BACKGROUND: Heat-shock protein B1 (HSPB1) is among the most well-known and versatile member of the evolutionarily conserved family of small heat-shock proteins. It has been implicated to serve a neuroprotective role against various neurological disorders via its modulatory activity on inflammation, yet its exact role in neuroinflammation is poorly understood. In order to shed light on the exact mechanism of inflammation modulation by HSPB1, we investigated the effect of HSPB1 on neuroinflammatory processes in an in vivo and in vitro model of acute brain injury. METHODS: In this study, we used a transgenic mouse strain overexpressing the human HSPB1 protein. In the in vivo experiments, 7-day-old transgenic and wild-type mice were treated with ethanol. Apoptotic cells were detected using TUNEL assay. The mRNA and protein levels of cytokines and glial cell markers were examined using RT-PCR and immunohistochemistry in the brain. We also established primary neuronal, astrocyte, and microglial cultures which were subjected to cytokine and ethanol treatments. TNFα and hHSPB1 levels were measured from the supernates by ELISA, and intracellular hHSPB1 expression was analyzed using fluorescent immunohistochemistry. RESULTS: Following ethanol treatment, the brains of hHSPB1-overexpressing mice showed a significantly higher mRNA level of pro-inflammatory cytokines (Tnf, Il1b), microglia (Cd68, Arg1), and astrocyte (Gfap) markers compared to wild-type brains. Microglial activation, and 1 week later, reactive astrogliosis was higher in certain brain areas of ethanol-treated transgenic mice compared to those of wild-types. Despite the remarkably high expression of pro-apoptotic Tnf, hHSPB1-overexpressing mice did not exhibit higher level of apoptosis. Our data suggest that intracellular hHSPB1, showing the highest level in primary astrocytes, was responsible for the inflammation-regulating effects. Microglia cells were the main source of TNFα in our model. Microglia isolated from hHSPB1-overexpressing mice showed a significantly higher release of TNFα compared to wild-type cells under inflammatory conditions. CONCLUSIONS: Our work provides novel in vivo evidence that hHSPB1 overexpression has a regulating effect on acute neuroinflammation by intensifying the expression of pro-inflammatory cytokines and enhancing glial cell activation, but not increasing neuronal apoptosis. These results suggest that hHSPB1 may play a complex role in the modulation of the ethanol-induced neuroinflammatory response.

Cerebrospinal fluid lipidomic biomarker signatures of demyelination for multiple sclerosis and Guillain-Barré syndrome.

Multiple sclerosis (MS) and Guillain-Barré syndrome (GBS) are demyelinating disorders affecting the central nervous system and peripheral nervous system (PNS), respectively. Cerebrospinal fluid (CSF) is one of the most valuable sources of diagnostic biomarkers in neurological diseases. In the present study high sensitivity shotgun mass spectrometry was used to characterise the CSF lipidome of patients with MS, GBS and controls with non-demyelinating diseases. The quantification of 222 CSF lipid molecular species revealed characteristic changes in the absolute and relative lipid concentrations in MS and GBS compared to the controls. For the GBS group, the fourfold elevation in the total lipid content was a discriminatory and a newly identified feature of PNS demyelination. In contrast, in MS, the accumulation of the myelin-derived cerebrosides represented a specific feature of demyelination. As a common feature of demyelination, we identified upregulated levels of lipid metabolic intermediates. We found strong positive correlation between total protein content and lipid concentrations in both diseases. By exploring the CSF lipidome we demonstrate usefulness of broad-range shotgun lipidomic analysis as a fast and reliable method of biomarker discovery in patients with demyelinating neurological disorders that might be a valuable diagnostic complement to existing examinations.

Lipid and protein tumor markers for head and neck squamous cell carcinoma identified by imaging mass spectrometry.

Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer worldwide. To improve pre- and post-operative diagnosis and prognosis novel molecular markers are desirable. Here we used MALDI imaging mass spectrometry (IMS) and immunohistochemistry (IHC) to seek tumor specific expression of proteins and lipids in HNSCC samples. Among low molecular weight proteins visualized, S100A8 and S100A9 were found to be expressed in the regions of tumor tissue but not in the surrounding healthy stroma of a post-operative microdissected tissue. Marker potential of S100A8 and S100A9 was confirmed by immunohistochemistry of paraffin-embedded pathological samples. Imaging lipids showed a remarkable depletion of lysophosphatidylcholine species LPC[16:0], LPC[18:2] and, in parallel, accumulation of major glycerophospholipid species PE-P[36:4], PC[32:1], PC[34:1] in neoplastic areas. This was confirmed by shotgun lipidomics of dissected healthy and tumor tissue sections. A combination of the negative (LPC[16:0]) and positive (PC[32:1], PC[34:1]) markers was also applicable to uncover tumorous character of a pre-operative biopsy. Furthermore, marker potential of lysophospholipids was supported by elevated expression levels of the lysophospholipid degrading enzyme lysophospholipase A1 (LYPLA1) in the tumor regions of paraffin-embedded HNSCC samples. Finally, experimental evidence of 3D cell spheroid tests showed that LPC[16:0] facilitates HNSCC invasion, implying that HNSCC progression in vivo may be dependent on lysophospholipid supply. Altogether, a series of novel proteins and lipid species were identified by IMS and IHC screening, which may serve as potential molecular markers for tumor diagnosis, prognosis, and may pave the way to better understand HNSCC pathophyisiology.

Membrane-Associated Heat Shock Proteins in Oncology: From Basic Research to New Theranostic Targets.

Heat shock proteins (HSPs) constitute a large family of conserved proteins acting as molecular chaperones that play a key role in intracellular protein homeostasis, regulation of apoptosis, and protection from various stress factors (including hypoxia, thermal stress, oxidative stress). Apart from their intracellular localization, members of different HSP families such as small HSPs, HSP40, HSP60, HSP70 and HSP90 have been found to be localized on the plasma membrane of malignantly transformed cells. In the current article, the role of membrane-associated molecular chaperones in normal and tumor cells is comprehensively reviewed with implications of these proteins as plausible targets for cancer therapy and diagnostics.

Modulation of Plasma Membrane Composition and Microdomain Organization Impairs Heat Shock Protein Expression in B16-F10 Mouse Melanoma Cells.

The heat shock response (HSR) regulates induction of stress/heat shock proteins (HSPs) to preserve proteostasis during cellular stress. Earlier, our group established that the plasma membrane (PM) acts as a sensor and regulator of HSR through changes in its microdomain organization. PM microdomains such as lipid rafts, dynamic nanoscale assemblies enriched in cholesterol and sphingomyelin, and caveolae, cholesterol-rich PM invaginations, constitute clustering platforms for proteins functional in signaling cascades. Here, we aimed to compare the effect of cyclodextrin (MßCD)- and nystatin-induced cholesterol modulations on stress-activated expression of the representative HSPs, HSP70, and HSP25 in mouse B16-F10 melanoma cells. Depletion of cholesterol levels with MßCD impaired the heat-inducibility of both HSP70 and HSP25. Sequestration of cholesterol with nystatin impaired the heat-inducibility of HSP25 but not of HSP70. Imaging fluorescent correlation spectroscopy marked a modulated lateral diffusion constant of fluorescently labelled cholesterol in PM during cholesterol deprived conditions. Lipidomics analysis upon MßCD treatment revealed, next to cholesterol reductions, decreased lysophosphatidylcholine and phosphatidic acid levels. These data not only highlight the involvement of PM integrity in HSR but also suggest that altered dynamics of specific cholesterol pools could represent a mechanism to fine tune HSP expression.