Journal of Membrane Biology最新文献

Glioblastoma (GBM) is a highly malignant primary brain tumor, and epidermal growth factor receptor (EGFR) is a well characterized biomaker on GBM. Treatment of GBM with EGFR inhibitors achieved limited efficacy due to low blood-brain barrier (BBB) permeability, and BBB-penetrant drugs are required. In this study, the BBB penetration of erlotinib and JN037 were studied using molecular dynamics method with explicit membrane model. The free energy profiles indicate that JCN037 has a lower central energy barrier than erlotinib, and it has a local minimum at lipid-water interface while erlotinib has not. Unconstrained MD simulations found that erlotinib prefers staying in water while JCN037 tends to interact with lipid molecules. Further analysis reveals that the Br atom of JCN037 plays an important role in its interaction with lipid molecules, and the adjacent F atom enhances the interaction of Br. The two flexible methoxyethoxy chains of erlotinib are responsible for its poor penetration. Our computational results agree well with the experimental results, providing useful information in the design and improvement of drugs with good BBB permeation.

The plasma membrane and autoinhibited Ca²⁺-ATPases contribute to the Ca²⁺ homeostasis in a wide variety of organisms. The enzymatic activity of these pumps is stimulated by calmodulin, which interacts with the target protein through the calmodulin-binding domain (CaMBD). Most information about this region is related to all calmodulin modulated proteins, which indicates general chemical properties and there is no established relation between Ca²⁺ pump sequences and taxonomic classification. Thus, the aim of this study was to perform an in silico analysis of the CaMBD from several Ca²⁺-ATPases, in order to determine their diversity and to detect specific patterns and amino acid selection in different species. Patterns related to potential and confirmed CaMBD were detected using sequences retrieved from the literature. The occurrence of these patterns was determined across 120 sequences from 17 taxonomical classes, which were analyzed by a phylogenetic tree to establish phylogenetic groups. Predicted physicochemical characteristics including hydropathy and net charge were calculated for each group of sequences. 22 Ca²⁺-ATPases sequences from animals, unicellular eukaryotes, and plants were retrieved from bioinformatic databases. These sequences allow us to establish the Patterns 1(GQILWVRGLTRLQTQ), 3(KNPSLEALQRW), and 4(SRWRRLQAEHVKK), which are present at the beginning of putative CaMBD of metazoan, parasites, and land plants. A pattern 2 (IRVVNAFR) was consistently found at the end of most analyzed sequences. The amino acid preference in the CaMBDs changed depending on the phylogenetic groups, with predominance of several aliphatic and charged residues, to confer amphiphilic properties. The results here displayed show a conserved mechanism to contribute to the Ca²⁺ homeostasis across evolution and may help to detect putative CaMBDs.

Nucleus is at the center stage of cellular drama orchestrated in the life of a cell and the nucleoplasm is surrounded by a double membranous compartment constituting the Nuclear membrane/envelope (NE) that separates it from the cytoplasm in nucleated cells. The initial understanding of the NE was that of a border security entity between the nucleus and the cytoplasm, separating gene regulation and transcription in the nucleus from translation in the cytoplasm. However, the discovery of a wide array of inherited diseases caused by mutations in genes encoding proteins that reside or interact with NE diverted the interest into deciphering the lipid-protein-rich environment of the NE. Today, the NE is considered a dynamic organelle which forms a functional linkage between the nucleus and the rest of the cell. The exposure of NE to constant mechanical constraints by its connectivity to the large polymer network of the lamina and chromatin on one side, and to the cytoskeleton on the other side results, in a variety of shape changes. We discuss two such deformation, the formation of nuclear blebs and nucleoplasmic reticulum (NER). Although the protein and the lipid composition of NE comprises a small fraction of the total lipid-protein load of the cell, the ability to define the lipid-protein composition of Inner nuclear membrane (INM) and Outer nuclear membrane (ONM) with precision is crucial for obtaining a deeper mechanistic understanding of their lipid-protein interaction and the various signaling pathways that are triggered by them. In addition, this allows us to further understand the direct and indirect roles of NE machinery in the chromosomal organization and gene regulation.

Plants have several mechanisms to endure salinity stress. The degree of salt tolerance varies significantly among different terrestrial crops. Proteins at the plant's cell wall and membrane mediate different physiological roles owing to their critical positioning between two distinct environments. A specific membrane protein is responsible for a single type of activity, such as a specific group of ion transport or a similar group of small molecule binding to exert multiple cellular effects. During salinity stress in plants, membrane protein functions: ion homeostasis, signal transduction, redox homeostasis, and solute transport are essential for stress perception, signaling, and recovery. Therefore, comprehensive knowledge about plant membrane proteins is essential to modulate crop salinity tolerance. This review gives a detailed overview of the membrane proteins involved in plant salinity stress highlighting the recent findings. Also, it discusses the role of solute transporters, accessory polypeptides, and proteins in salinity tolerance. Finally, some aspects of membrane proteins are discussed with potential applications to developing salt tolerance in crops.

Macrophages are the predominant component of innate immunity, which is an important protective barrier of our body. Macrophages are present in all organs and tissues of the body, their main functions include immune surveillance, bacterial killing, tissue remodeling and repair, and clearance of cell debris. In addition, macrophages can present antigens to T cells and facilitate inflammatory response by releasing cytokines. Macrophages are of high concern due to their crucial roles in multiple physiological processes. In recent years, new advances are emerging after great efforts have been made to explore the mechanisms of macrophage activation. Ion channel is a class of multimeric transmembrane protein that allows specific ions to go through cell membrane. The flow of ions through ion channel between inside and outside of cell membrane is required for maintaining cell morphology and intracellular signal transduction. Expressions of various ion channels in macrophages have been detected. The roles of ion channels in macrophage activation are gradually caught attention. K⁺ channels are the most studied channels in immune system. However, very few of published papers reviewed the studies of K⁺ channels on macrophages. Here, we will review the four types of K⁺ channels that are expressed in macrophages: voltage-gated K⁺ channel, calcium-activated K⁺ channel, inwardly rectifying K⁺ channel and two-pore domain K⁺ channel.

Chloride channel-3 (ClC-3) Cl^-/H⁺ antiporters and leucine-rich repeat-containing 8 (LRRC8) family anion channels have both been associated with volume-regulated anion currents (VRACs). VRACs are often altered in ClC-3 null cells but are absent in LRRC8A null cells. To explore the relationship between ClC-3, LRRC8A, and VRAC we localized tagged proteins in human epithelial kidney (HEK293) cells using multimodal microscopy. Expression of ClC-3-GFP induced large multivesicular bodies (MVBs) with ClC-3 in the delimiting membrane. LRRC8A-RFP localized to the plasma membrane and to small cytoplasmic vesicles. Co-expression demonstrated co-localization in small, highly mobile cytoplasmic vesicles that associated with the early endosomal marker Rab5A. However, most of the small LRRC8A-positive vesicles were constrained within large MVBs with abundant ClC-3 in the delimiting membrane. Dominant negative (S34A) Rab5A prevented ClC-3 overexpression from creating enlarged MVBs, while constitutively active (Q79L) Rab5A enhanced this phenotype. Thus, ClC-3 and LRRC8A are endocytosed together but independently sorted in Rab5A MVBs. Subsequently, LRRC8A-labeled vesicles were sorted to MVBs labeled by Rab27A and B exosomal compartment markers, but not to Rab11 recycling endosomes. VRAC currents were significantly larger in ClC-3 null HEK293 cells. This work demonstrates dependence of LRRC8A trafficking on ClC-3 which may explain the association between ClC-3 and VRACs.

Cholesterol is the most representative sterol present in membranes of higher eukaryotes, and is the end product of a long and multistep biosynthetic pathway. Lathosterol and zymosterol are biosynthetic precursors of cholesterol in Kandutsch-Russell and Bloch pathways, respectively. Lathosterol differs with cholesterol merely in the position of the double bond in the sterol ring, whereas zymosterol differs with cholesterol in position and number of double bonds. In this work, we have monitored the effect of cholesterol and its biosynthetic precursors (lathosterol and zymosterol) on membrane organization and dynamics in fluid and gel phase membranes. Toward this goal, we have utilized two fluorescent membrane probes, DPH and its cationic derivative TMA-DPH. Our results using these probes show that cholesterol and its biosynthetic precursors (lathosterol and zymosterol) exhibit similar trend in maintaining membrane organization and dynamics (as reported by fluorescence anisotropy and apparent rotational correlation time), in fluid phase POPC membranes. Notably, although lathosterol and zymosterol show similar trend in maintaining membrane organization and dynamics, the corresponding change for cholesterol is different in gel phase DPPC membranes. These results demonstrate that the position and number of double bonds in sterols is an important determinant in maintaining membrane physical properties. Our results assume significance since accumulation of precursors of cholesterol have been reported to be associated with severe pathological conditions.