Journal of Membrane Biology最新文献

{"title":"Pore Formation by Pore Forming Proteins in Lipid Membranes: Structural Insights Through Cryo-EM.","authors":"Arnab Chatterjee, Prasenjit Naskar, Suman Mishra, Somnath Dutta","doi":"10.1007/s00232-025-00344-5","DOIUrl":"https://doi.org/10.1007/s00232-025-00344-5","url":null,"abstract":"<p><p>Many pathogenic bacteria utilize their complicated appalling arsenal, bacterial virulence factors, to attack host cells by damaging the host cell membrane and neutralizing host defense mechanisms. Bacterial pore-forming proteins (PFPs) are one of them, they include a distinct class of secreted soluble toxin monomers, which binds to the specific cell surface receptors and /or lipids, oligomerizes as an amphipathic transmembrane pore complex on host cell membranes, and deforms the integrity of the plasma membrane. Researchers have focused on characterizing the structure and function of different Pore Forming Toxins (PFTs) from various organisms, where most of the structural studies employed X-ray crystallography, single-particle cryo-EM, and cryo-electron tomography. However, historically, most of these previous studies focused on using detergent to solubilize and oligomerize the PFTs. Additionally, previous studies have also shown that lipid membranes and lipid components, including cell surface receptors, play a critical role in pore formation and oligomerization. However, there are limited studies available that aim to resolve the structure and function of PFTs in liposomes. In this review article, we majorly focused on structural and functional studies of pore-forming toxins in the presence of detergents, lipid nanodiscs, and liposomes. We will also discuss the challenges and benefits of using liposomes to study pore-forming proteins in more biologically relevant membrane environments.</p>","PeriodicalId":50129,"journal":{"name":"Journal of Membrane Biology","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143744156","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Action of the Terminal Complement Pathway on Cell Membranes.","authors":"Bill H T Ho, Bradley A Spicer, Michelle A Dunstone","doi":"10.1007/s00232-025-00343-6","DOIUrl":"https://doi.org/10.1007/s00232-025-00343-6","url":null,"abstract":"<p><p>The complement pathway is one of the most ancient elements of the host's innate response and includes a set of protein effectors that rapidly react against pathogens. The late stages of the complement reaction are broadly categorised into two major outcomes. Firstly, C5a receptors, expressed on membranes of host cells, are activated by C5a to generate pro-inflammatory responses. Secondly, target cells are lysed by a hetero-oligomeric pore known as the membrane attack complex (MAC) that punctures the cellular membrane, causing ion and osmotic flux. Generally, several membrane-bound and soluble inhibitors protect the host membrane from complement damage. This includes inhibitors against the MAC, such as clusterin and CD59. This review addresses the most recent molecular and structural insights behind the activation and modulation of the integral membrane proteins, the C5a receptors (C5aR1 and C5aR2), as well as the regulation of MAC assembly. The second aspect of the review focuses on the molecular basis behind inflammatory diseases that are reflective of failure to regulate the terminal complement effectors. Although each arm is unique in its function, both pathways may share similar outcomes in these diseases. As such, the review outlines potential synergy and crosstalk between C5a receptor activation and MAC-mediated cellular responses.</p>","PeriodicalId":50129,"journal":{"name":"Journal of Membrane Biology","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2025-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143694291","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Structural Dynamics of the Slide Helix of Inactive/Closed Conformation of KirBac1.1 in Micelles and Membranes: A Fluorescence Approach.","authors":"Arpan Bysack, Chandrima Jash, H Raghuraman","doi":"10.1007/s00232-024-00335-y","DOIUrl":"10.1007/s00232-024-00335-y","url":null,"abstract":"<p><p>Inward rectifying potassium (Kir) channels play a critical role in maintaining the resting membrane potential and cellular homeostasis. The high-resolution crystal structure of homotetrameric KirBac1.1 in detergent micelles provides a snapshot of the closed state. Similar to micelles, KirBac1.1 is reported to be in the inactive/closed conformation in POPC membranes. The slide helix of KirBac1.1 is an important structural motif that regulates channel gating. Despite the importance of slide helix in lipid-dependent gating, conflicting models have emerged for the location of slide helix and its structural dynamics in membrane mimetics is poorly understood. Here, we monitored the structural dynamics of the slide helix (residues 46-57) of KirBac1.1 in both DM micelles and POPC membranes utilizing various site-directed fluorescence approaches. We show, using ACMA-based liposome-flux assay, the cysteine mutants of the slide helix are not functional, ensuring the inactive/closed conformation in POPC membranes similar to wild-type channel. Time-resolved fluorescence and water accessibility measurements of NBD-labeled single-cysteine mutants of slide-helix residues suggest that the location of the slide helix at the interfacial region might be shallower in membranes compared to micelles. Interestingly, the slide helix of KirBac1.1 is more dynamic in the physiologically relevant membrane environment, which is accompanied by a differential hydration dynamics throughout the slide helix. Further, REES and lifetime distribution analyses suggest significant changes in conformational heterogeneity of the slide helix in membrane mimetics. Overall, our results give an insight into how membrane mimetics affect the organization and dynamics of slide helix of the closed state of KirBac1.1, and highlight the importance of lipid-protein interactions in membranes.</p>","PeriodicalId":50129,"journal":{"name":"Journal of Membrane Biology","volume":" ","pages":"97-112"},"PeriodicalIF":2.3,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11779782/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142958182","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sphingomyelin Inhibits Hydrolytic Activity of Heterodimeric PLA₂ in Model Myelin Membranes: Pharmacological Relevance.","authors":"Anwaar S Chaudary, Yanglin Guo, Yuri N Utkin, Maryam Barancheshmeh, Ruben K Dagda, Edward S Gasanoff","doi":"10.1007/s00232-024-00327-y","DOIUrl":"10.1007/s00232-024-00327-y","url":null,"abstract":"<p><p>In this work, the heterodimeric phospholipase A₂, HDP-2, from viper venom was investigated for its hydrolytic activity in model myelin membranes as well as for its effects on intermembrane exchange of phospholipids (studied by phosphorescence quenching) and on phospholipid polymorphism (studied by ¹H-NMR spectroscopy) to understand the role of sphingomyelin (SM) in the demyelination of nerve fibers. By using well-validated in vitro approaches, we show that the presence of SM in model myelin membranes leads to a significant inhibition of the hydrolytic activity of HDP-2, decreased intermembrane phospholipid exchange, and reduced phospholipid polymorphism. Using AutoDock software, we show that the NH^δ+ group of the sphingosine backbone of SM binds to Tyr22(C=O_pb^δ-) of HDP-2 via a hydrogen bond which keeps only the polar head of SM inside the HDP-2's active center and positions the sn-2 acyl ester bond away from the active center, thus making it unlikely to hydrolyze the alkyl chains at the sn-2 position. This observation strongly suggests that SM inhibits the catalytic activity of HDP-2 by blocking access to other phospholipids to the active center of the enzyme. Should this observation be verified in further studies, it would offer a tantalizing opportunity for developing effective pharmaceuticals to stop the demyelination of nerve fibers by aberrant PLA₂s with overt activity - as observed in brain degenerative diseases - by inhibiting SM hydrolysis and/or facilitating SM synthesis in the myelin sheath membrane.</p>","PeriodicalId":50129,"journal":{"name":"Journal of Membrane Biology","volume":" ","pages":"29-46"},"PeriodicalIF":2.3,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142512121","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Computational Insights on the Assembly of the Dengue Virus Membrane-Capsid-RNA Complex.","authors":"Dwaipayan Chaudhuri, Satyabrata Majumder, Joyeeta Datta, Kalyan Giri","doi":"10.1007/s00232-025-00337-4","DOIUrl":"10.1007/s00232-025-00337-4","url":null,"abstract":"<p><p>Dengue virus, an arbovirus from the genus Flavivirus in the family Flaviviridae, forms a nucleocapsid structure through interactions between its genome and multiple copies of the capsid protein. Experimental studies have confirmed the interaction between the viral capsid protein and lipid droplets, indicating a protein-lipid interaction. Cryo-EM studies show that in immature viruses, the nucleocapsid is located close to the viral membrane. This study uses multiple MD simulations to explore the orientation of the capsid protein relative to the lipid membrane, focusing on how the protein's hydrophobic pocket interacts with the membrane. We also investigated the interaction between the capsid protein and RNA, considering the effects of sequence length and identity. Finally, we construct a model of the lipid-protein-RNA complex, demonstrating that the capsid protein's hydrophobic pocket interacts with the membrane, while the positively charged H4 helix interacts with the negatively charged RNA. This research may identify crucial interactions for immature virus particle formation and provide insights for future therapeutic interventions.</p>","PeriodicalId":50129,"journal":{"name":"Journal of Membrane Biology","volume":" ","pages":"75-96"},"PeriodicalIF":2.3,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143015344","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cell-Free Systems and Their Importance in the Study of Membrane Proteins.","authors":"Karen Stephania González-Ponce, Samuel Celaya-Herrera, María Fernanda Mendoza-Acosta, Luz Edith Casados-Vázquez","doi":"10.1007/s00232-024-00333-0","DOIUrl":"10.1007/s00232-024-00333-0","url":null,"abstract":"<p><p>The Cell-Free Protein Synthesis (CFPS) is an innovative technique used to produce various proteins. It has several advantages, including short expression times, no strain engineering is required, and toxic proteins such as membrane proteins can be produced. However, the most important advantage is that it eliminates the need for a living cell as a production system. Membrane proteins (MPs) are difficult to express in heterologous strains such as Escherichia coli. Modified strains must be used, and sometimes the strain produces them as inclusion bodies, which makes purification difficult. CFPS can avoid the problem of toxicity and, with the use of additives, allows the production of folded and functional membrane proteins. In this review, we focus on describing what cell-free systems are. We address the advantages and disadvantages of the different organisms that can be used to obtain cell extracts, including PURE systems, where the components are obtained recombinantly, and the methodologies that allow the synthesis of membrane proteins in cell-free systems, which, given their hydrophobic nature, require additives for their correct folding.</p>","PeriodicalId":50129,"journal":{"name":"Journal of Membrane Biology","volume":" ","pages":"15-28"},"PeriodicalIF":2.3,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142933414","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Role of the Swollen State in Cell Proliferation.","authors":"Behor Eleazar Cohen","doi":"10.1007/s00232-024-00328-x","DOIUrl":"10.1007/s00232-024-00328-x","url":null,"abstract":"<p><p>Cell swelling is known to be involved in various stages of the growth of plant cells and microorganisms but in mammalian cells how crucial a swollen state is for determining the fate of the cellular proliferation remains unclear. Recent evidence has increased our understanding of how the loss of the cell surface interactions with the extracellular matrix at early mitosis decreases the membrane tension triggering curvature changes in the plasma membrane and the activation of the sodium/hydrogen (Na +/H +) exchanger (NHE1) that drives osmotic swelling. Such a swollen state is temporary, but it is critical to alter essential membrane biophysical parameters that are required to activate Ca2 + channels and modulate the opening of K + channels involved in setting the membrane potential. A decreased membrane potential across the mitotic cell membrane enhances the clustering of Ras proteins involved in the Ca2 + and cytoskeleton-driven events that lead to cell rounding. Changes in the external mechanical and osmotic forces also have an impact on the lipid composition of the plasma membrane during mitosis.</p>","PeriodicalId":50129,"journal":{"name":"Journal of Membrane Biology","volume":" ","pages":"1-13"},"PeriodicalIF":2.3,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142559268","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Pharmacodynamic characterization and evaluation of oxidative stress effects of digitoxigenin derivatives on HeLa cells.","authors":"Jessica M M Valadares, Pedro Azalim-Neto, Xiaofan Liu, Nathallia Cavalcanti Carrozza, George A O'Doherty, Luis Eduardo M Quintas, Leandro A Barbosa","doi":"10.1007/s00232-024-00334-z","DOIUrl":"10.1007/s00232-024-00334-z","url":null,"abstract":"<p><p>Cancer is a leading cause of death worldwide and its treatment is hampered by the lack of specificity and side effects of current drugs. Cardiotonic steroids (CTS) interact with Na⁺/K⁺-ATPase (NKA) and induce antineoplastic effects, but their narrow therapeutic window is key limiting factor. The synthesis of digitoxigenin derivatives with glycosidic unit modifications is a promising approach to develop more selective and effective antitumor agents. This study aimed to compare the pharmacological properties as well as the cytotoxic effects of digitoxigenin-α-L-amiceto-pyranoside and digitoxigenin-α-L-rhamno-pyranoside and to evaluate the mechanism of these derivatives in oxidative conditions in HeLa cells. The rhamnose derivative increased the binding affinity and inhibitory effect of digitoxigenin by approximately 5-15 times, unlike the amicetose derivative. Despite this difference, both compounds similarly increased H₂O₂ levels, induced membrane lipid peroxidation, and reduced GSH levels and SOD activity at nanomolar concentrations. This study highlights the importance of the sugar moiety in CTS structure for NKA binding and demonstrates that a primary mechanism of cytotoxicity of digitoxigenin derivatives may involve cellular oxidative stress, underscoring their potential as therapeutic agents for cancer treatment.</p>","PeriodicalId":50129,"journal":{"name":"Journal of Membrane Biology","volume":" ","pages":"63-73"},"PeriodicalIF":2.3,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142985342","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of Triterpenoids Betulin and Betulinic Acid on Pulmonary Surfactant Membranes.","authors":"Cisem Altunayar-Unsalan, Ozan Unsalan","doi":"10.1007/s00232-024-00329-w","DOIUrl":"10.1007/s00232-024-00329-w","url":null,"abstract":"<p><p>The purpose of this work is to examine how triterpenoids betulin (BE) and betulinic acid (BA) affect the thermotropic phase behaviour and bilayer packing in pulmonary surfactant membranes. Therefore, the interaction of these triterpenoids with dipalmitoylphosphatidylcholine (DPPC) bilayers is studied by differential scanning calorimetry (DSC), attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), and quantum chemical computations with density functional theory (DFT). From DSC data, the effects are more pronounced with BE compared to BA. At BE concentration of 20 mol%, the pretransition does not completely disappear and the lamellar phase transition broadens further. There are two indistinguishable peaks in the main phase transition, which may indicate the start of inhomogeneous mixing or phase separation in the gel phase. BA reduces the main transition temperature and almost completely eliminates the pretransition at concentrations of 1-10 mol%. Endotherms continue to have a symmetric, broad form that suggests perfect mixing. From ATR-FTIR data, both triterpenoids display the CH₂ antisymmetric stretching, C = O stretching, PO₂^- asymmetric stretching to higher wavenumber in DPPC system. These results indicate an increase in the lateral mobility and dehydration in the polar head group and glycerol-acyl chain interface of DPPC liposomes. From microscopic results, it is found that the addition of high concentration (20 mol%) of BE and BA into pure DPPC membranes, single and double planar layers are formed, and the size of the liposomes increases. According to computational studies, the O₁₃₁-H₂₀₆ OH group of BE and the P₂₄-O₂₆ head group of DPPC formed a hydrogen bonding of 1.805 Å between BE and DPPC in gas phase. This hydrogen bonding is observed between BA and DPPC via the P₂₄-O₂₆ head group of DPPC and the O₁₃₂-H₂₀₉ OH group of BA.</p>","PeriodicalId":50129,"journal":{"name":"Journal of Membrane Biology","volume":" ","pages":"47-61"},"PeriodicalIF":2.3,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142792757","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hetero-Oligomeric Protein Pores for Single-Molecule Sensing.","authors":"Remya Satheesan, Asuma Janeena, Kozhinjampara R Mahendran","doi":"10.1007/s00232-024-00331-2","DOIUrl":"https://doi.org/10.1007/s00232-024-00331-2","url":null,"abstract":"<p><p>Protein nanopores are emerging as versatile single-molecule sensors with broad applications in DNA and protein sequencing. However, their narrow size restricts the range of detectable analytes, necessitating the development of advanced nanopores to broaden their applications in biotechnology. This review highlights a natural hetero-oligomeric porin, Nocardia farcinica porin AB (NfpAB), based on the Gram-positive mycolata, Nocardia farcinica. The pore comprises two subunits, NfpA and NfpB, that combine to form a stable structure with a unique pore geometry, asymmetrical shape, and charge distribution. Single-channel electrical recordings demonstrate that NfpAB forms stable, high-conductance channels suitable for sensing charged molecules, particularly cationic polypeptides and cyclic sugars. This pore offers advantages such as enhanced control over molecular interactions due to densely crowded charged residues, thus allowing the quantification of voltage-dependent translocation kinetics. Notably, NfpAB contains intrinsic cysteines in the pore lumen, providing an accessible site for thiol-based reactions and attachment of molecular adapters. We propose that such hetero-oligomeric pores will be effective for several applications in nanopore technology for biomolecular detection and sequencing.</p>","PeriodicalId":50129,"journal":{"name":"Journal of Membrane Biology","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142856535","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}