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Signal Transduction and Targeted Therapy Jun 2023T lymphopenia, occurring in the early phase of sepsis in response to systemic inflammation, is commonly associated with morbidity and mortality of septic infections. We...
T lymphopenia, occurring in the early phase of sepsis in response to systemic inflammation, is commonly associated with morbidity and mortality of septic infections. We have previously shown that a sufficient number of T cells is required to constrain Toll-like receptors (TLRs) mediated hyperinflammation. However, the underlying mechanisms remains unsolved. Herein, we unveil that CD4 T cells engage with MHC II of macrophages to downregulate TLR pro-inflammatory signaling. We show further that the direct contact between CD4 molecule of CD4 T cells or the ectodomain of CD4 (soluble CD4, sCD4), and MHC II of resident macrophages is necessary and sufficient to prevent TLR4 overactivation in LPS and cecal ligation puncture (CLP) sepsis. sCD4 serum concentrations increase after the onset of LPS sepsis, suggesting its compensatory inhibitive effects on hyperinflammation. sCD4 engagement enables the cytoplasmic domain of MHC II to recruit and activate STING and SHP2, which inhibits IRAK1/Erk and TRAF6/NF-κB activation required for TLR4 inflammation. Furthermore, sCD4 subverts pro-inflammatory plasma membrane anchorage of TLR4 by disruption of MHC II-TLR4 raft domains that promotes MHC II endocytosis. Finally, sCD4/MHCII reversal signaling specifically interferes with TLR4 but not TNFR hyperinflammation, and independent of the inhibitive signaling of CD40 ligand of CD4 cells on macrophages. Therefore, a sufficient amount of soluble CD4 protein can prevent excessive inflammatory activation of macrophages via alternation of MHC II-TLR signaling complex, that might benefit for a new paradigm of preventive treatment of sepsis.
Topics: Humans; CD4 Antigens; Toll-Like Receptor 4; Lipopolysaccharides; Macrophages; Sepsis; Inflammation
PubMed: 37332010
DOI: 10.1038/s41392-023-01438-z -
Neurologia 2023Rafts are protein-lipid structural nanodomains involved in efficient signal transduction and the modulation of physiological processes of the cell plasma membrane. Raft... (Review)
Review
INTRODUCTION
Rafts are protein-lipid structural nanodomains involved in efficient signal transduction and the modulation of physiological processes of the cell plasma membrane. Raft disruption in the nervous system has been associated with a wide range of disorders.
DEVELOPMENT
We review the concept of rafts, the nervous system processes in which they are involved, and their role in diseases such as Parkinson's disease, Alzheimer disease, and Huntington disease.
CONCLUSIONS
Based on the available evidence, preservation and/or reconstitution of rafts is a promising treatment strategy for a wide range of neurological disorders.
Topics: Humans; Caveolae; Membrane Microdomains; Cholesterol; Cell Membrane; Alzheimer Disease
PubMed: 37858892
DOI: 10.1016/j.nrleng.2023.10.003 -
Chemistry and Physics of Lipids Jul 2023Labyrinthopeptins constitute a class of ribosomal synthesized peptides belonging to the type III family of lantibiotics. They exist in different variants and display...
Labyrinthopeptins constitute a class of ribosomal synthesized peptides belonging to the type III family of lantibiotics. They exist in different variants and display broad antiviral activities as well as show antiallodynic activity. Although their mechanism of action is not understood, it has been described that Labyrinthopeptins interact with membrane phospholipids modulating its biophysical properties and point out to membrane destabilization as its main point of action. We have used all-atom molecular dynamics to study the location of labyrinthopeptin A2 in a complex membrane as well as the existence of specific interactions with membrane lipids. Our results indicate that labyrinthopeptin A2, maintaining its globular structure, tends to be placed at the membrane interface, mainly between the phosphate atoms of the phospholipids and the oxygen atom of cholesterol modulating the biophysical properties of the membrane lipids. Outstandingly, we have found that labyrinthopeptin A2 tends to be preferentially surrounded by sphingomyelin while excluding cholesterol. The bioactive properties of labyrinthopeptin A2 could be attributed to the specific disorganization of raft domains in the membrane and the concomitant disruption of the overall membrane organization. These results support the improvement of Labyrinthopeptins as therapeutic molecules, opening up new opportunities for future medical advances.
Topics: Membrane Lipids; Phospholipids; Bacteriocins; Cholesterol; Membrane Microdomains
PubMed: 37061155
DOI: 10.1016/j.chemphyslip.2023.105303 -
FEBS Open Bio Sep 2023Gangliosides are functional components of membrane lipid rafts that control critical functions in cell communication. Many pathologies involve raft gangliosides, which... (Review)
Review
Gangliosides are functional components of membrane lipid rafts that control critical functions in cell communication. Many pathologies involve raft gangliosides, which therefore represent an approach of choice for developing innovative therapeutic strategies. Beginning with a discussion of what a disease is (and is not), this review lists the major human pathologies that involve gangliosides, which includes cancer, diabetes, and infectious and neurodegenerative diseases. In most cases, the problem is due to a protein whose binding to gangliosides either creates a pathological condition or impairs a physiological function. Then, I draw up an inventory of the different molecular mechanisms of protein-ganglioside interactions. I propose to classify the ganglioside-binding domains of proteins into four categories, which I name GBD-1, GBD-2, GBD-3, and GBD-4. This structural and functional classification could help to rationalize the design of innovative molecules capable of disrupting the binding of selected proteins to gangliosides without generating undesirable effects. The biochemical specificities of gangliosides expressed in the human brain must also be taken into account to improve the reliability of animal models (or any animal-free alternative) of Alzheimer's and Parkinson's diseases.
Topics: Humans; Gangliosides; Reproducibility of Results; Parkinson Disease; Brain; Membrane Microdomains
PubMed: 37052878
DOI: 10.1002/2211-5463.13612 -
Aging Nov 2023Recently we have shown that adipokine visfatin-induced NLRP3 inflammasome activation contributes to podocyte injury. However, the molecular mechanisms of how...
Recently we have shown that adipokine visfatin-induced NLRP3 inflammasome activation contributes to podocyte injury. However, the molecular mechanisms of how visfatin-induces the Nlrp3 inflammasome activation and podocyte damage is still unknown. The present study tested whether membrane raft (MR) redox signalling pathway plays a central role in visfatin-induced NLRP3 inflammasomes formation and activation in podocytes. Upon visfatin stimulation an aggregation of NADPH oxidase subunits, gp91phox and p47phox was observed in the membrane raft (MR) clusters, forming a MR redox signalling platform in podocytes. The formation of this signalling platform was blocked by prior treatment with MR disruptor MCD or NADPH oxidase inhibitor DPI. In addition, visfatin stimulation significantly increased the colocalization of Nlrp3 with Asc or Nlrp3 with caspase-1, IL-β production, cell permeability in podocytes compared to control cells. Pretreatment with MCD, DPI, WEHD significantly abolished the visfatin-induced colocalization of NLRP3 with Asc or NLRP3 with caspase-1, IL-1β production and cell permeability in podocytes. Furthermore, Immunofluorescence analysis demonstrated that visfatin treatment significantly decreased the podocin and nephrin expression (podocyte damage) and prior treatments with DPI, WEHD, MCD attenuated this visfatin-induced podocin and nephrin reduction. In conclusion, our results suggest that visfatin stimulates membrane raft clustering in the membrane of podocytes to form redox signaling platforms by aggregation and activation of NADPH oxidase subunits enhancing O production and leading to NLRP3 inflammasome activation in podocytes and ultimate podocyte injury.
Topics: Inflammasomes; Podocytes; NLR Family, Pyrin Domain-Containing 3 Protein; Nicotinamide Phosphoribosyltransferase; NADPH Oxidases; Caspase 1; Oxidation-Reduction
PubMed: 38032896
DOI: 10.18632/aging.205243 -
Cells Jan 2024Glaucoma is a group of ocular diseases that cause irreversible blindness. It is characterized by multifactorial degeneration of the optic nerve axons and retinal... (Review)
Review
Glaucoma is a group of ocular diseases that cause irreversible blindness. It is characterized by multifactorial degeneration of the optic nerve axons and retinal ganglion cells (RGCs), resulting in the loss of vision. Major components of glaucoma pathogenesis include glia-driven neuroinflammation and impairment of mitochondrial dynamics and bioenergetics, leading to retinal neurodegeneration. In this review article, we summarize current evidence for the emerging role of apolipoprotein A-I binding protein (AIBP) as an important anti-inflammatory and neuroprotective factor in the retina. Due to its association with toll-like receptor 4 (TLR4), extracellular AIBP selectively removes excess cholesterol from the plasma membrane of inflammatory and activated cells. This results in the reduced expression of TLR4-associated, cholesterol-rich lipid rafts and the inhibition of downstream inflammatory signaling. Intracellular AIBP is localized to mitochondria and modulates mitophagy through the ubiquitination of mitofusins 1 and 2. Importantly, elevated intraocular pressure induces AIBP deficiency in mouse models and in human glaucomatous retina. AIBP deficiency leads to the activation of TLR4 in Müller glia, triggering mitochondrial dysfunction in both RGCs and Müller glia, and compromising visual function in a mouse model. Conversely, restoring AIBP expression in the retina reduces neuroinflammation, prevents RGCs death, and protects visual function. These results provide new insight into the mechanism of AIBP function in the retina and suggest a therapeutic potential for restoring retinal AIBP expression in the treatment of glaucoma.
Topics: Mice; Animals; Humans; Toll-Like Receptor 4; Neuroinflammatory Diseases; Glaucoma; Retina; Cholesterol
PubMed: 38275823
DOI: 10.3390/cells13020198 -
International Journal of Molecular... Jul 2023This paper deals with the problems encountered in the study of eukaryotic cell membranes. A discussion on the structure and composition of membranes, lateral... (Review)
Review
This paper deals with the problems encountered in the study of eukaryotic cell membranes. A discussion on the structure and composition of membranes, lateral heterogeneity of membranes, lipid raft formation, and involvement of actin and cytoskeleton networks in the maintenance of membrane structure is included. Modern methods for the study of membranes and their constituent domains are discussed. Various simplified models of biomembranes and lipid rafts are presented. Computer modelling is considered as one of the most important methods. This is stated that from the study of the plasma membrane structure, it is desirable to proceed to the diverse membranes of all organelles of the cell. The qualitative composition and molar content of individual classes of polar lipids, free sterols and proteins in each of these membranes must be considered. A program to create an open access electronic database including results obtained from the membrane modelling of individual cell organelles and the key sites of the membranes, as well as models of individual molecules composing the membranes, has been proposed.
Topics: Eukaryotic Cells; Cholesterol; Cell Membrane; Sterols; Membrane Microdomains; Computer Simulation
PubMed: 37446404
DOI: 10.3390/ijms241311226 -
Biochemical and Biophysical Research... Jul 2023The interplay between membrane subregions and receptor tyrosine kinases (RTK) will influence signaling in both normal and pathological RTK conditions. In this study,...
The interplay between membrane subregions and receptor tyrosine kinases (RTK) will influence signaling in both normal and pathological RTK conditions. In this study, epidermal growth factor receptor (EGFR) and platelet-derived growth factor receptor β (PDGFR-β) internalizations were investigated by immunofluorescent microscopy following simultaneous treatment with EGF and PDGF-BB. We found that the two receptors utilize separate routes of internalization, which merges in a common perinuclear endosomal compartment after 45 min of stimulation. This is further strengthened when contrasting the recruitment of either EGFR or PDGFR-β to either clathrin or caveolin-1: PDGFR-β dissociates from caveolin-1 upon stimulation, and engages clathrin, whilst an increased recruitment of EGFR, to both clathrin and caveolin-1, was observed upon EGF stimulation. The association between EGFR and caveolin-1 is supported by the observation that EGFR was localized in lipid raft associated fractions, whereas PDGFR-β was not. We also found that disruption of lipid rafts using MβCD led to an increased EGFR dimerization and phosphorylation in response to ligand, as well as a dramatic decrease in AKT- and a smaller but robust decrease in ERK1/2 phosphorylation. This suggest that lipid rafts may be important to effectively connect the EGFR with downstream proteins to facilitate signaling. Our data implies that cholesterol depletion of the plasma membrane affect the signaling of EGFR and PDGFRβ differently.
Topics: Proto-Oncogene Proteins c-akt; Caveolin 1; Epidermal Growth Factor; MAP Kinase Signaling System; ErbB Receptors; Phosphorylation; Receptor, Platelet-Derived Growth Factor beta; Clathrin; Cholesterol
PubMed: 37163940
DOI: 10.1016/j.bbrc.2023.04.099 -
Microbiology Spectrum Aug 2023Many eukaryotic membrane-dependent functions are often spatially and temporally regulated by membrane microdomains (FMMs), also known as lipid rafts. These domains are...
Many eukaryotic membrane-dependent functions are often spatially and temporally regulated by membrane microdomains (FMMs), also known as lipid rafts. These domains are enriched in polyisoprenoid lipids and scaffolding proteins belonging to the tomatin, rohibitin, lotillin, and flK/C (SPFH) protein superfamily that was also identified in Gram-positive bacteria. In contrast, little is still known about FMMs in Gram-negative bacteria. In Escherichia coli K-12, 4 SPFH proteins, YqiK, QmcA, HflK, and HflC, were shown to localize in discrete polar or lateral inner membrane locations, raising the possibility that E. coli SPFH proteins could contribute to the assembly of inner membrane FMMs and the regulation of cellular processes. Here, we studied the determinant of the localization of QmcA and HflC and showed that FMM-associated cardiolipin lipid biosynthesis is required for their native localization pattern. Using Biolog phenotypic arrays, we showed that a mutant lacking all SPFH genes displayed increased sensitivity to aminoglycosides and oxidative stress that is due to the absence of HflKC. Our study therefore provides further insights into the contribution of SPFH proteins to stress tolerance in E. coli. Eukaryotic cells often segregate physiological processes in cholesterol-rich functional membrane microdomains. These domains are also called lipid rafts and contain proteins of the tomatin, rohibitin, lotillin, and flK/C (SPFH) superfamily, which are also present in prokaryotes but have been mostly studied in Gram-positive bacteria. Here, we showed that the cell localization of the SPFH proteins QmcA and HflKC in the Gram-negative bacterium E. coli is altered in the absence of cardiolipin lipid synthesis. This suggests that cardiolipins contribute to E. coli membrane microdomain assembly. Using a broad phenotypic analysis, we also showed that HflKC contribute to E. coli tolerance to aminoglycosides and oxidative stress. Our study, therefore, provides new insights into the cellular processes associated with SPFH proteins in E. coli.
Topics: Escherichia coli Proteins; Escherichia coli; Prohibitins; Aminoglycosides; Cardiolipins; Escherichia coli K12; Membrane Microdomains; Oxidative Stress; Anti-Bacterial Agents
PubMed: 37347165
DOI: 10.1128/spectrum.01767-23 -
Cellular & Molecular Biology Letters Oct 2023Membrane rafts play a crucial role in the regulation of many important biological processes. Our previous data suggest that specific interactions of flotillins with MPP1...
BACKGROUND
Membrane rafts play a crucial role in the regulation of many important biological processes. Our previous data suggest that specific interactions of flotillins with MPP1 are responsible for membrane raft domain organization and regulation in erythroid cells. Interaction of the flotillin-based protein network with specific membrane components underlies the mechanism of raft domain formation and regulation, including in cells with low expression of MPP1.
METHODS
We sought to identify other flotillin partners via the immobilized recombinant flotillin-2-based affinity approach and mass spectrometry technique. The results were further confirmed via immunoblotting and via co-immunoprecipitation. In order to study the effect of the candidate protein on the physicochemical properties of the plasma membrane, the gene was knocked down via siRNA, and fluorescence lifetime imaging microscopy and spot-variation fluorescence correlation spectroscopy was employed.
RESULTS
EFR3A was identified as a candidate protein that interacts with flotillin-2. Moreover, this newly discovered interaction was demonstrated via overlay assay using recombinant EFR3A and flotillin-2. EFR3A is a stable component of the detergent-resistant membrane fraction of HeLa cells, and its presence was sensitive to the removal of cholesterol. While silencing the EFR3A gene, we observed decreased order of the plasma membrane of living cells or giant plasma membrane vesicles derived from knocked down cells and altered mobility of the raft probe, as indicated via fluorescence lifetime imaging microscopy and spot-variation fluorescence correlation spectroscopy. Moreover, silencing of EFR3A expression was found to disturb epidermal growth factor receptor and phospholipase C gamma phosphorylation and affect epidermal growth factor-dependent cytosolic Ca concentration.
CONCLUSIONS
Altogether, our results suggest hitherto unreported flotillin-2-EFR3A interaction, which might be responsible for membrane raft organization and regulation. This implies participation of this interaction in the regulation of multiple cellular processes, including those connected with cell signaling which points to the possible role in human health, in particular human cancer biology.
Topics: Humans; Cell Membrane; Epidermal Growth Factor; HeLa Cells; Protein Binding; Membrane Microdomains; Adaptor Proteins, Signal Transducing; Membrane Proteins
PubMed: 37880612
DOI: 10.1186/s11658-023-00497-y