Interaction of Hsp90 with phospholipid model membranes

Identification and functional characterization of putative ligand binding domain(s) of JlpA protein of Campylobacter jejuni

Among the major Surface Exposed Colonization Proteins (SECPs) of Campylobacter jejuni (C. jejuni), Jejuni lipoprotein A (JlpA) plays a crucial role in host cell adhesion specifically by binding to the N-terminal domain of the human heat shock protein 90α (Hsp90α-NTD). Although the JlpA binding to Hsp90α activates NF-κB and p38 MAP kinase pathways, the underlying mechanism of JlpA association with the cellular receptor remains unclear. To this end, we predicted two potential receptor binding sites within the C-terminal domain of JlpA: one spanning from amino acid residues Q332-A354 and the other from S258-T295; however, the latter exhibited weaker binding. To assess the functional attributes of these predicted sequences, we generated two JlpA mutants (JlpAΔ1: S258-T295; JlpAΔ2: Q332-A354) and assessed the Hsp90α-binding affinity-kinetics by in vitro and ex vivo experiments. Our findings confirmed that the residues Q332-A354 are of greater importance in host cell adhesion with a measurable impact on cellular responses. Further, thermal denaturation by circular dichroism (CD) confirmed that the reduced binding affinity of the JlpAΔ2 to Hsp90α is not associated with protein folding or stability. Together, this study provides a possible framework for determining the molecular function of designing rational inhibitors efficiently targeting JlpA.

Impact of Biogenic and Chemogenic Selenium Nanoparticles on Model Eukaryotic Lipid Membranes

Microbial nanotechnology is an expanding research area devoted to producing biogenic metal and metalloid nanomaterials (NMs) using microorganisms. Often, biogenic NMs are explored as antimicrobial, anticancer, or antioxidant agents. Yet, most studies focus on their applications rather than the underlying mechanism of action or toxicity. Here, we evaluate the toxicity of our well-characterized biogenic selenium nanoparticles (bSeNPs) produced by the Stenotrophomonas maltophilia strain SeITE02 against the model yeast Saccharomyces cerevisiae comparing it with chemogenic SeNPs (cSeNPs). Knowing from previous studies that the biogenic extract contained bSeNPs in an organic material (OM) and supported here by Fourier transform infrared spectroscopy, we removed and incubated it with cSeNPs (cSeNPs_OM) to assess its influence on the toxicity of these formulations. Specifically, we focused on the first stages of the eukaryotic cell exposure to these samples─i.e., their interaction with the cell lipid membrane, which was mimicked by preparing vesicles from yeast polar lipid extract or phosphatidylcholine lipids. Fluidity changes derived from biogenic and chemogenic samples revealed that the bSeNP extract mediated the overall rigidification of lipid vesicles, while cSeNPs showed negligible effects. The OM and cSeNPs_OM induced similar modifications to the bSeNP extract, reiterating the need to consider the OM influence on the physical-chemical and biological properties of bSeNP extracts.

Interaction of Macromolecular Chain with Phospholipid Membranes in Solutions: A Dissipative Particle Dynamics Simulation Study

The interaction between macromolecular chains and phospholipid membranes in aqueous solution was investigated using dissipative particle dynamics simulations. Two cases were considered, one in which the macromolecular chains were pulled along parallel to the membrane surfaces and another in which they were pulled vertical to the membrane surfaces. Several parameters, including the radius of gyration, shape factor, particle number, and order parameter, were used to investigate the interaction mechanisms during the dynamics processes by adjusting the pulling force strength of the chains. In both cases, the results showed that the macromolecular chains undergo conformational transitions from a coiled to a rod-like structure. Furthermore, the simulations revealed that the membranes can be damaged and repaired during the dynamic processes. The role of the pulling forces and the adsorption interactions between the chains and membranes differed in the parallel and perpendicular pulling cases. These findings contribute to our understanding of the interaction mechanisms between macromolecules and membranes, and they may have potential applications in biology and medicine.

A joint proteomic and genomic investigation provides insights into the mechanism of calcification in coccolithophores

Coccolithophores are globally abundant, calcifying microalgae that have profound effects on marine biogeochemical cycles, the climate, and life in the oceans. They are characterized by a cell wall of CaCO3 scales called coccoliths, which may contribute to their ecological success. The intricate morphologies of coccoliths are of interest for biomimetic materials synthesis. Despite the global impact of coccolithophore calcification, we know little about the molecular machinery underpinning coccolithophore biology. Working on the model Emiliania huxleyi, a globally distributed bloom-former, we deploy a range of proteomic strategies to identify coccolithogenesis-related proteins. These analyses are supported by a new genome, with gene models derived from long-read transcriptome sequencing, which revealed many novel proteins specific to the calcifying haptophytes. Our experiments provide insights into proteins involved in various aspects of coccolithogenesis. Our improved genome, complemented with transcriptomic and proteomic data, constitutes a new resource for investigating fundamental aspects of coccolithophore biology.

The Heat Shock Transcription Factor HsfA Plays a Role in Membrane Lipids Biosynthesis Connecting Thermotolerance and Unsaturated Fatty Acid Metabolism in Aspergillus fumigatus

Thermotolerance is a remarkable virulence attribute of Aspergillus fumigatus, but the consequences of heat shock (HS) to the cell membrane of this fungus are unknown, although this structure is one of the first to detect changes in ambient temperature that imposes on the cell a prompt adaptative response. Under high-temperature stress, fungi trigger the HS response controlled by heat shock transcription factors, such as HsfA, which regulates the expression of heat shock proteins. In yeast, smaller amounts of phospholipids with unsaturated fatty acid (FA) chains are synthesized in response to HS, directly affecting plasma membrane composition. The addition of double bonds in saturated FA is catalyzed by Δ9-fatty acid desaturases, whose expression is temperature-modulated. However, the relationship between HS and saturated/unsaturated FA balance in membrane lipids of A. fumigatus in response to HS has not been investigated. Here, we found that HsfA responds to plasma membrane stress and has a role in sphingolipid and phospholipid unsaturated biosynthesis. In addition, we studied the A. fumigatus Δ9-fatty acid desaturase sdeA and discovered that this gene is essential and required for unsaturated FA biosynthesis, although it did not directly affect the total levels of phospholipids and sphingolipids. sdeA depletion significantly sensitizes mature A. fumigatus biofilms to caspofungin. Also, we demonstrate that hsfA controls sdeA expression, while SdeA and Hsp90 physically interact. Our results suggest that HsfA is required for the adaptation of the fungal plasma membrane to HS and point out a sharp relationship between thermotolerance and FA metabolism in A. fumigatus. IMPORTANCE Aspergillus fumigatus causes invasive pulmonary aspergillosis, a life-threatening infection accounting for high mortality rates in immunocompromised patients. The ability of this organism to grow at elevated temperatures is long recognized as an essential attribute for this mold to cause disease. A. fumigatus responds to heat stress by activating heat shock transcription factors and chaperones to orchestrate cellular responses that protect the fungus against damage caused by heat. Concomitantly, the cell membrane must adapt to heat and maintain physical and chemical properties such as the balance between saturated/unsaturated fatty acids. However, how A. fumigatus connects these two physiological responses is unclear. Here, we explain that HsfA affects the synthesis of complex membrane lipids such as phospholipids and sphingolipids and controls the enzyme SdeA, which produces monounsaturated fatty acids, raw material for membrane lipids. These findings suggest that forced dysregulation of saturated/unsaturated fatty acid balance might represent novel strategies for antifungal therapy.

Improving animal welfare status and meat quality through assessment of stress biomarkers: A critical review

Stress induces various physiological and biochemical alterations in the animal body, which are used to assess the stress status of animals. Blood profiles, serum hormones, enzymes, and physiological conditions such as body temperature, heart, and breathing rate of animals are the most commonly used stress biomarkers in the livestock sector. Previous exposure, genetics, stress adaptation, intensity, duration, and rearing practices result in wide intra- and inter-animal variations in the expression of various stress biomarkers. The use of meat proteomics by adequately analyzing the expression of various muscle proteins such as heat shock proteins (HSPs), acute phase proteins (APPs), texture, and tenderness biomarkers help predict meat quality and stress in animals before slaughter. Thus, there is a need to identify non-invasive, rapid, and accurate stress biomarkers that can objectively assess stress in animals. The present manuscript critically reviews various aspects of stress biomarkers in animals and their application in mitigating preslaughter stress in meat production.

Effects of heat stress on cyto(chemo)kine and inflammasome gene expression and mechanical properties in isolated red and white blood cells from 4 commercial broiler lines and their ancestor jungle fowl

Commercial broilers have been selected for high growth rate and productivity; however, this has negatively impacted their susceptibility to heat stress (HS). Insight into the molecular mechanisms underlying this vulnerability can help design targeted strategies for improvement of HS tolerance. Red blood cells (RBC) and white blood cells (WBC) were isolated from red jungle fowl and 4 lines of commercial modern broilers. Lines A and B are considered standard-yielding lines, whereas Lines C and D are high-yielding. Cells were cultured at either 37°C or 45°C for 2 h to induce heat stress (HS). Gene expression of cytokines, chemokines, and inflammasome components were measured. Heat shock proteins 27 and 70 (HSPs) in RBC were significantly affected by line (P < 0.05), whereas HSP27 and 60 were affected by temperature (P < 0.05). In WBC, there was a significant line effect on HSP gene expression (P < 0.05), and a significant increase (P < 0.05) in HSP90 in Line D in HS compared to TN conditions. In RBC, there was a main effect of HS on TNFα, CCL4, and CCLL4 (P < 0.05). HS significantly increased IL-8L1 (>30-fold, P < 0.0001) in Line C. Inflammasome genes (NLRP3, NLRC5 and NLRC3) were significantly affected by the line studied (P < 0.05). In WBC, the effect of line was significant for all cytokines, chemokines, and inflammasome components studied (P < 0.05). To examine the mechanical properties of isolated RBC from the 4 commercial lines and jungle fowl, RBC were placed into nematic liquid crystals, where Lines B and D were the most strained, and Line A and the jungle fowl were the least strained. Together, these findings indicate not only the dynamic nature of circulating cells, but the differences in the stress and inflammatory response among commercially available lines and their common ancestor. These profiles have the potential to serve as a future marker for stress responses in broilers, though further study is warranted.

The interaction of heat shock proteins with cellular membranes: a historical perspective

The interaction of heat shock proteins (HSP) with cellular membranes has been an enigmatic process, initially observed by morphological studies, inferred during the purification of HSP70s, and confirmed after the detection of these proteins on the surface of cancer cells and their insertion into artificial lipid bilayers. Today, the association of several HSP with lipid membranes is well established. However, the mechanisms for membrane insertion have been elusive. There is conclusive evidence indicating that HSP70s have a great selectivity for negatively charged phospholipids, whereas other HSP have a broader spectrum of lipid specificity. HSP70 also oligomerizes upon membrane insertion, forming ion conductance channels. The functional role of HSP70 lipid interactions appears related to membrane stabilization that may play a role during cell membrane biogenesis. They could also play a role as membrane chaperones as well as during endocytosis, microautophagy, and signal transduction. Moreover, HSP membrane association is a key component in the extracellular export of these proteins. The presence of HSP70 on the surface of cancer cells and its interaction with lysosome membranes have been envisioned as potential therapeutic targets. Thus, the biology and function of HSP membrane association are reaching a new level of excitement. This review is an attempt to preserve the recollection of the pioneering contributions of many investigators that have participated in this endeavor.

Human heat shock cognate protein (HSC70/HSPA8) interacts with negatively charged phospholipids by a different mechanism than other HSP70s and brings HSP90 into membranes

Heat shock proteins (HSP) are critical elements for the preservation of cellular homeostasis by participating in an array of biological processes. In addition, HSP play an important role in cellular protection from various environmental stresses. HSP are part of a large family of different molecular mass polypeptides, displaying various expression patterns, subcellular localizations, and diversity functions. An unexpected observation was the detection of HSP on the cell surface. Subsequent studies have demonstrated that HSP have the ability to interact and penetrate lipid bilayers by a process initiated by the recognition of phospholipid heads, followed by conformational changes, membrane insertion, and oligomerization. In the present study, we described the interaction of HSPA8 (HSC70), the constitutive cytosolic member of the HSP70 family, with lipid membranes. HSPA8 showed high selectivity for negatively charged phospholipids, such as phosphatidylserine and cardiolipin, and low affinity for phosphatidylcholine. Membrane insertion was mediated by a spontaneous process driven by increases in entropy and diminished by the presence of ADP or ATP. Finally, HSPA8 was capable of driving into the lipid bilayer HSP90 that does not display any lipid biding capacity by itself. This observation suggests that HSPA8 may act as a membrane chaperone.

Tethered Lipid Membranes as a Nanoscale Arrangement towards Non-Invasive Analysis of Acute Pancreatitis

Extracellular heat shock proteins (HSPs) mediate immunological functions and are involved in pathologies such as infection, stress, and cancer. Here, we demonstrated the dependence of an amount of HSP70 and HSP90 in serum vs. severity of acute pancreatitis (AP) on a cohort of 49 patients. Tethered bilayer lipid membranes (tBLMs) have been developed to investigate HSPs’ interactions with tBLMs that can be probed by electrochemical impedance spectroscopy (EIS). The results revealed that HSP70 and HSP90 interact via different mechanisms. HSP70 shows the damage of the membrane, while HSP90 increases the insulation properties of tBLM. These findings provide evidence that EIS offers a novel approach for the study of the changes in membrane integrity induced by HSPs proteins. Herein, we present an alternative electrochemical technique, without any immunoprobes, that allows for the monitoring of HSPs on nanoscaled tBLM arrangement in biologics samples such us human urine. This study demonstrates the great potential of tBLM to be used as a membrane based biosensor for novel, simple, and non-invasive label-free analytical system for the prediction of AP severity.

iTRAQ-based proteomic analysis of duck muscle related to lipid oxidation

Lipid oxidation is the main cause of quality deterioration in meat and meat products. To facilitate the identification of candidate molecular biomarkers that are linked to lipid oxidation, we performed the proteomic analysis of duck muscle using isobaric tag for relative and absolute quantification (iTRAQ), followed by parallel reaction monitoring (PRM) to confirm the iTRAQ results. Pectoralis major muscles were divided into 2 groups in accordance with lipid oxidation, and iTRAQ-based analysis identified a total of 301 differentially expressed proteins, of which 15 proteins were examined by PRM assay. Proteins involved in lipid binding and metabolism, lipolysis, stress response, oxidative respiratory chain, and redox regulation were found to be differentially expressed between 2 groups and might affect lipid oxidation in muscles. The findings could contribute to the improved understanding of key proteins and processes engaged in lipid oxidation of meat.

Characterization of the Relationship between the Chaperone and Lipid-Binding Functions of the 70-kDa Heat-Shock Protein, HspA1A

HspA1A, a molecular chaperone, translocates to the plasma membrane (PM) of stressed and cancer cells. This translocation results in HspA1A’s cell-surface presentation, which renders tumors radiation insensitive. To specifically inhibit the lipid-driven HspA1A’s PM translocation and devise new therapeutics it is imperative to characterize the unknown HspA1A’s lipid-binding regions and determine the relationship between the chaperone and lipid-binding functions. To elucidate this relationship, we determined the effect of phosphatidylserine (PS)-binding on the secondary structure and chaperone functions of HspA1A. Circular dichroism revealed that binding to PS resulted in minimal modification on HspA1A’s secondary structure. Measuring the release of inorganic phosphate revealed that PS-binding had no effect on HspA1A’s ATPase activity. In contrast, PS-binding showed subtle but consistent increases in HspA1A’s refolding activities. Furthermore, using a Lysine-71-Alanine mutation (K71A; a null-ATPase mutant) of HspA1A we show that although K71A binds to PS with affinities similar to the wild-type (WT), the mutated protein associates with lipids three times faster and dissociates 300 times faster than the WT HspA1A. These observations suggest a two-step binding model including an initial interaction of HspA1A with lipids followed by a conformational change of the HspA1A-lipid complex, which accelerates the binding reaction. Together these findings strongly support the notion that the chaperone and lipid-binding activities of HspA1A are dependent but the regions mediating these functions do not overlap and provide the basis for future interventions to inhibit HspA1A’s PM-translocation in tumor cells, making them sensitive to radiation therapy.

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.

Evaluation of antioxidant property of heat shock protein 90 from duck muscle

OBJECTIVE

The objectives of this study were to investigate the direct antioxidative effect of 90 Kda heat shock protein (Hsp90) obtained from duck muscle.

METHODS

The interaction of Hsp90 with phospholipids and oxidized phospholipids was studied with surface plasmon resonance (SPR), and their further oxidation in the presence of Hsp90 was evaluated with thiobarbituric acid reactive substances (TBARS) assay. The scavenging effect on the 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azinobis (3-ethylbenzthiazoline-6-sulfonic acid (ABTS) was measured, and the electron paramagnetic resonance (EPR) spectroscopy in combination with 5-tert-Butoxycarbonyl-5-methyl-1-pyrroline-N-oxide and 2-phenyl-4,4,5,5,-tetramethylimidazoline-1-oxyl-3-oxide (PTIO) was utilized to determine the abilities of Hsp90 in scavenging hydroxyl and PTIO radicals.

RESULTS

SPR showed Hsp90 could bind with both phospholipids and oxidized phospholipids, and prevent their further oxidation by the TBARS assay. The DPPH and ABTS scavenging activity increased with Hsp90 concentration, and could reach 27% and 20% respectively at the protein concentration of 50 μM. The EPR spectra demonstrated Hsp90 could directly scavenge ·OH and PTIO· radicals.

CONCLUSION

This suggests that Hsp90, a natural antioxidant in meat, may play an important role in cellular defense against oxidative stress, and may have potential use in meat products.

Molecular chaperones in the brain endothelial barrier: neurotoxicity or neuroprotection?

Brain microvascular endothelial cells (BMECs) interact with astrocytes and pericytes to form the blood-brain barrier (BBB). Their compromised function alters the BBB integrity, which is associated with early events in the pathogenesis of cancer, neurodegenerative diseases, and epilepsy. Interestingly, these conditions also induce the expression of heat shock proteins (HSPs). Here we review the contribution of major HSP families to BMEC and BBB function. Although investigators mainly report protective effects of HSPs in brain, contrasted results were obtained in BMEC, which depend both on the HSP and on its location, intra- or extracellular. The therapeutic potential of HSPs must be scrupulously analyzed before targeting them in patients to reduce the progression of brain lesions and improve neurologic outcomes in the long term.-Thuringer, D., Garrido, C. Molecular chaperones in the brain endothelial barrier: neurotoxicity or neuroprotection?

Hsp70 interactions with membrane lipids regulate cellular functions in health and disease

Beyond guarding the cellular proteome the major stress inducible heat shock protein Hsp70 has been shown to interact with lipids. Non-cytosolic Hsp70 stabilizes membranes during stress challenges and, in pathophysiological states, facilitates endocytosis, counteracts apoptotic mechanisms, sustains survival pathways or represents a signal that can be recognized by the immune system. Disease-coupled lipid-associated functions of Hsp70 may be targeted via distinct subcellular localizations of Hsp70 itself or its specific interacting lipids. With a special focus on interacting lipids, here we discuss localization-dependent roles of the membrane-bound Hsp70 in the context of its therapeutic potential, particularly in cancer and neurodegenerative diseases.

Stress Effects on Meat Quality: A Mechanistic Perspective

Stress inevitably occurs from the farm to abattoir in modern livestock husbandry. The effects of stress on the behavioral and physiological status and ultimate meat quality have been well documented. However, reports on the mechanism of stress effects on physiological and biochemical changes and their consequent effects on meat quality attributes have been somewhat disjointed and limited. Furthermore, the causes of variability in meat quality traits among different animal species, muscle fibers within an animal, and even positions within a piece of meat in response to stress are still not entirely clear. This review 1st summarizes the primary stress factors, including heat stress, preslaughter handling stress, oxidative stress, and other stress factors affecting animal welfare; carcass quality; and eating quality. This review further delineates potential stress-induced pathways or mediators, including AMP-activated protein kinase-mediated energy metabolism, crosstalk among calcium signaling pathways and reactive oxygen species, protein modification, apoptosis, calpain and cathepsin proteolytic systems, and heat shock proteins that exert effects that cause biochemical changes during the early postmortem period and affect the subsequent meat quality. To obtain meat of high quality, further studies are needed to unravel the intricate mechanisms involving the aforementioned signaling pathways or mediators and their crosstalk.