Journal of Membrane Biology最新文献

Aggressive cancer cells such as pancreatic cells exhibit an enhanced metastatic phenotype that involves cell migration and invasion. Cellular membrane deformation is a key process implicit in cell movement. This implicates a link between altered lipid metabolism during cancer progression and modulated membrane properties and hence associated functions. One of the key factors underlying the aggressiveness of pancreatic cancer is the presence of the highest percentage of hypoxia, which further adds to the lipid metabolic reprogramming. The subsequent effect of hypoxia-induced lipidome changes on membrane properties governing cell movement was investigated in this work using a combination of cell biology, microscopy, and spectroscopy. Our findings revealed that hypoxia induces distinct lipidome signatures in a cell-line-dependent fashion, which in turn differentially modulates the cell membrane stiffness. The correlation of cell stiffness with other membrane properties and the actin cytoskeleton shows a random correlation indicating that hypoxic stress distinctly regulates specific membrane attributes governing cellular functioning and should be consulted for the development of effective treatments for pancreatic cancer.

The growing antimicrobial resistance presents a challenge in developing new potent drugs, but this effort is hindered by a lack of information regarding how these new drugs would behave in biomembranes. Surfactants are considered mimetic models for biomembranes and can be used to study drug-membrane interactions. In this study, we used two well-known surfactants-cationic cetyltrimethylammonium bromide and anionic sodium dodecyl sulfate-as model membranes to investigate their interaction with the antimicrobial drug ofloxacin (OFL). These interactions were studied using volumetric and acoustic methods over the temperature range of 293.15-323.15 K to determine the apparent molar volume, isentropic compressibility, apparent molar compressibility, acoustic impedance, relative association, and intermolecular free length. Furthermore, UV-Vis spectroscopy and cyclic voltammetry were employed to evaluate the binding constants and free energies of the drug-surfactant systems. These results provide key molecular insights into the thermodynamics of OFL partitioning and its binding mechanisms with amphiphilic assemblies. Such mechanistic understanding is crucial for the rational design of antibiotic delivery systems, facilitating precise control over drug loading and release dynamics in surfactant-based formulations.

Chlamydia trachomatis is an obligate intracellular Gram-negative pathogen that causes sexually transmitted infections (STIs) and trachoma. Current interventions are limited due to the widespread nature of asymptomatic infections, and the absence of a licensed vaccine exacerbates the challenge. In this study, we predicted outer membrane β-barrel (OMBB) proteins and designed a multi-epitope vaccine (MEV) construct using identified proteins. We employed a consensus-based computational framework on the C. trachomatis D/UW-3/CX proteome and identified 17 OMBB proteins, including well-known Pmp family members and MOMP. Eight OMBB proteins were computationally characterized, showing significant structural homology with known outer membrane proteins from other bacteria. Sequence-based annotation tools were used to determine their putative functions. B-cell and T-cell epitopes were predicted from the selected proteins. The MEV construct was designed using four cytotoxic T-lymphocyte (CTL) epitopes and 29 helper T-lymphocyte (HTL) epitopes from six OMBB proteins, which were conserved across 106 C. trachomatis serovars. To enhance its immunogenicity, the vaccine was supplemented with the Cholera toxin B subunit and PADRE sequence at the N-terminus. The MEV construct, of length 780 amino acids, was predicted to be antigenic, non-allergenic, non-toxic, and soluble. Secondary structure analysis revealed 95% random coils. A three-dimensional structural model of the MEV was generated and subsequently validated. Molecular docking between MEV and toll-like receptor 4 (TLR4) revealed strong and stable binding interactions. The MEV-TLR4 complex was found to be structurally compact and stable using molecular dynamics simulation. Immune simulation of the MEV construct elicited a strong immune response. This study highlights OMBB proteins as promising immunogenic targets and presents a computationally designed MEV candidate for C. trachomatis infection.

Insect venom-derived antimicrobial peptides (AMPs) hold significant therapeutic promise, but their application is constrained by mammalian cell toxicity. Toxicity assays are rapid and high-throughput, but screening large peptide libraries remains resource-intensive due to the requirements for peptide synthesis, purification, and testing. Alternatively, molecular dynamics (MD) simulations using mammalian membrane models provide an efficient and robust method for preliminary toxicity prediction. To benchmark the optimal model, two distinct mammalian membrane systems with diverse lipid compositions were evaluated for a set of sixteen toxic and fourteen non-toxic AMP analogs from five distinct insect AMP families, viz. anoplin, polybia, halictine, hyline, and macropin. In this study, a total of 25 µs of MD simulation time was generated. The analysis of MD trajectories, each spanning 500 ns for each of the 30 peptides, revealed significant variations in structural stability and membrane permeability between toxic and non-toxic AMPs, which aligned with the experimental results. Root Mean Square Deviation (RMSD) of the peptides during the last 100 ns of the simulation period successfully distinguished toxic from non-toxic AMPs with 90% accuracy when using realistic membrane models. The well-cited multicomponent mammalian membrane model failed to effectively predict mammalian toxicity. These findings underscore the efficacy of MD simulations in predicting the toxicity of venom-derived AMPs, thereby opening avenues for the accelerated development of safer antimicrobial therapies.

Yeasts are able to tolerate different environmental conditions, including stress situations. Given their broad applications in the food industry, their ability to adapt to stressful conditions is an active area of research. Lipid composition of the yeast membrane is affected by environmental stress, and thus, the regulation of the membrane biophysical properties under such conditions may be a key point for yeast adaptation. Although Saccharomyces cerevisiae is highly tolerant to ethanol, its growth is inhibited when this alcohol accumulates in the medium. Therefore, we studied the effect of ethanol on yeast membranes using the fluorescent probe Laurdan, which is sensitive to water dipolar relaxation. Three strains were used: a laboratory strain of S. cerevisiae (BY4741), a mutant that lacks ergosterol (erg6 $\Delta$ ), and a commercial baker's yeast. At low ethanol levels, the emission signal of the probe remained constant for all strains. For ethanol proportions higher than 20% (v/v), at which cells are no longer viable, the signal changed abruptly, indicating an increase in solvent dipolar relaxation. We further studied BY4741 yeasts acclimated to high ethanol levels and found that water was more ordered in these membranes than in BY4741 grown in the absence of ethanol. We propose that water structure and membrane hydration are key for yeast viability in the presence of ethanol, and that studying the biophysical properties of membranes could be useful to identify yeast strains with a high tolerance to ethanol.

Fatty acid Transport Protein 3 (FATP3) is a single-pass transmembrane protein implicated in the uptake and intracellular transport of long-chain fatty acids, yet the molecular contribution of its transmembrane domain (TMD) remains poorly defined. Here, we establish an efficient and reproducible strategy for heterologous expression, purification, and in vitro reconstitution of FATP3-TMD. FATP3-TMD was over-expressed in Escherichia coli as a TrpLE fusion, liberated by cyanogen-bromide cleavage and polished by one-step reverse-phase HPLC, yielding milligram quantities of highly pure peptide. ¹H-¹⁵N HSQC spectroscopy revealed a well-folded FATP3-TMD in both Fos-choline-14 micelles and DMPC/DHPC bicelles. Strikingly, titration with docosahexaenoic acid (DHA) induced residue-specific chemical-shift perturbations exclusively in bicelles. These data demonstrate that a bilayer-like lipid context is essential for functional recognition of ω-3 fatty acids by the FATP3-TMD and provide a robust platform for mechanistic dissection of FATP3 mediated lipid transport.

Fifty years ago, Erwin Neher and Bert Sakmann published a Nature paper on their recording of discrete, step-like currents of a few picoamps passing through individual acetylcholine receptor channels of frog muscle fibers. This observation, the first on native channels, immediately ended the decade-long dispute about the presence of ion channels on cell membranes by convincing even the most reluctant scientists that this was indeed the case. More importantly, however, the ability to record single-channel currents revolutionized the study of ion channels because it enabled scientists to observe their behavior individually in real time. We could observe them change conformation, jumping from the closed state to the open state and back again. This level of detail provided an unprecedented understanding of the gating mechanisms, conductance, and kinetic properties of channels. This retrospective illustrates the scientific context in which all of this occurred as well as its immediate and current impact on the investigation of ion channels.

Stomatin, encoded by STOM gene, is an integral membrane protein found in a wide variety of species. Although years have passed since the identification of stomatin, little has been known about the functional insights of stomatin among which stomatin undergoing homo-oligomerization, post and reverse-post modifications are the notable ones. Stomatin downregulation or overexpression is directly connected to its ability to control neutrophil degranulation, modulate activities of transporter proteins, and mediate cancer metastasis. Stomatin shares about 40-80% sequence similarity at its signature SPFH (stomatin, prohibitin, flotillin and Hlfk) domain region with the stomatin-like proteins (SLPs). Although stomatin and SLPs are reported to have various therapeutic activities, still gaps are there regarding their plausible mechanistic insights. Therefore, in future, studies should be aimed toward investigating the possible mechanistic pathways controlled by stomatin and SLPs which can be employed to understand the basis of many therapeutic targets. This review briefs about the different functions of stomatin focusing mainly on the transporter proteins and carcinogenicity modulation by stomatin and SLPs.

Coronaviruses use the spike protein (spike) to bind to target cells, and fuse the viral envelope with a host lipid membrane. Spike is a large trimeric surface glycoprotein, anchored to the viral membrane (envelope) by a single membrane-spanning polypeptide helix and a short intra-virion domain. In the SARS-CoV-2 virus, the spike is formed by three protomers of 1273 residues, each with two distinct domains separable by enzymatic proteolysis prior to infection. Thus far, enveloped virus surface glycoprotein structures have provided a detailed molecular view of the pre-fusion state, while structures of the post-fusion state have remained incomplete. The determination of the full-length structure of the SARS-CoV-2 spike in the post-fusion state is a landmark in furthering our understanding of the structural pre-requisites for membrane fusion. This perspective analyzes the fusion domain as revealed by the recent structure in the context of conserved sequences across diverse coronaviruses. We highlight the characterization of the membrane-embedded fusion peptide in a helical hairpin topology. This structure is discussed as a re-imagination of the helical hairpin hypothesis for polypeptide insertion into membranes, postulated by Engleman and Steitz over four decades ago.