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Biochimica Et Biophysica Acta.... Oct 2018In this article we review current understanding of basic principles for the folding of membrane proteins, focusing on the more abundant alpha-helical class. Membrane... (Review)
Review
In this article we review current understanding of basic principles for the folding of membrane proteins, focusing on the more abundant alpha-helical class. Membrane proteins, vital to many biological functions and implicated in numerous diseases, fold into their active conformations in the complex environment of the cell bilayer membrane. While many membrane proteins rely on the translocon and chaperone proteins to fold correctly, others can achieve their functional form in the absence of any translation apparatus or other aides. Nevertheless, the spontaneous folding process is not well understood at the molecular level. Recent findings suggest that helix fraying and loop formation may be important for overall structure, dynamics and regulation of function. Several types of membrane helices with ionizable amino acids change their topology with pH. Additionally we note that some peptides, including many that are rich in arginine, and a particular analogue of gramicidin, are able passively to translocate across cell membranes. The findings indicate that a final protein structure in a lipid-bilayer membrane is sequence-based, with lipids contributing to stability and regulation. While much progress has been made toward understanding the folding process for alpha-helical membrane proteins, it remains a work in progress. This article is part of a Special Issue entitled: Emergence of Complex Behavior in Biomembranes edited by Marjorie Longo.
Topics: Amino Acid Sequence; Amino Acids; Cell Membrane; Hydrogen-Ion Concentration; Lipid Bilayers; Membrane Proteins; Membranes; Models, Molecular; Peptides; Protein Conformation; Protein Conformation, alpha-Helical; Protein Folding; Protein Structure, Secondary
PubMed: 29447916
DOI: 10.1016/j.bbamem.2018.02.010 -
Molecules (Basel, Switzerland) Aug 2022This review is an attempt to incorporate water as a structural and thermodynamic component of biomembranes. With this purpose, the consideration of the membrane... (Review)
Review
This review is an attempt to incorporate water as a structural and thermodynamic component of biomembranes. With this purpose, the consideration of the membrane interphase as a bidimensional hydrated polar head group solution, coupled to the hydrocarbon region allows for the reconciliation of two theories on cells in dispute today: one considering the membrane as an essential part in terms of compartmentalization, and another in which lipid membranes are not necessary and cells can be treated as a colloidal system. The criterium followed is to describe the membrane state as an open, non-autonomous and responsive system using the approach of Thermodynamic of Irreversible Processes. The concept of an open/non-autonomous membrane system allows for the visualization of the interrelationship between metabolic events and membrane polymorphic changes. Therefore, the Association Induction Hypothesis (AIH) and lipid properties interplay should consider hydration in terms of free energy modulated by water activity and surface (lateral) pressure. Water in restricted regions at the lipid interphase has thermodynamic properties that explain the role of H-bonding networks in the propagation of events between membrane and cytoplasm that appears to be relevant in the context of crowded systems.
Topics: Lipid Bilayers; Lipids; Membranes; Thermodynamics; Water
PubMed: 35956945
DOI: 10.3390/molecules27154994 -
Biochimica Et Biophysica Acta.... Jun 2019The phospholipase A (PLA) family comprises a group of lipolytic enzymes that typically hydrolyze the sn-2 position of (glycerol) phospholipids to give rise to fatty... (Review)
Review
The phospholipase A (PLA) family comprises a group of lipolytic enzymes that typically hydrolyze the sn-2 position of (glycerol) phospholipids to give rise to fatty acids and lysophospholipids. The mammalian genome encodes more than 30 (even 50) PLAs or related enzymes, which are classified into several subfamilies on the basis of their structures and functions. The PLA family has been implicated not only in signal transduction by producing lipid mediators, but also in membrane homeostasis, energy production, and barrier function. Disturbance of PLA-regulated lipid pathways often hampers tissue and cellular homeostasis and can be linked to various diseases. This special issue overviews the current state of understanding of the classification, enzymatic properties, and physiological functions of various enzymes belonging to the PLA family. This article is part of a Special Issue entitled Novel functions of phospholipase A Guest Editors: Makoto Murakami and Gerard Lambeau.
Topics: Animals; Humans; Lipids; Membranes; Phospholipases A2; Signal Transduction
PubMed: 30769093
DOI: 10.1016/j.bbalip.2019.02.005 -
Cell and Tissue Research Jul 2017The last 5 years have witnessed tremendous advances in both light- and electron-microscopic techniques in the biomedical sciences. Application of these new cutting-edge... (Review)
Review
The last 5 years have witnessed tremendous advances in both light- and electron-microscopic techniques in the biomedical sciences. Application of these new cutting-edge methods to glomerular biology has advanced considerably and, in part, completed our endeavor to draw a detailed map of the glomerular tuft. The scope of this review is to illustrate these new insights within both the morphometry of podocyte cells and the architecture of the glomerular filtration barrier and to assess whether these findings have indeed had an impact on our biological understanding of glomerular function.
Topics: Animals; Glomerular Basement Membrane; Humans; Podocytes
PubMed: 28283912
DOI: 10.1007/s00441-017-2590-3 -
Cardiac Electrophysiology Clinics Sep 2020In patients with nonischemic cardiomyopathy, epicardial ablation is critical in targeting epicardial paravalvular substrate. Epicardial access and ablation can be... (Review)
Review
In patients with nonischemic cardiomyopathy, epicardial ablation is critical in targeting epicardial paravalvular substrate. Epicardial access and ablation can be performed safely with attention to epicardial structures, such as the coronary arteries, phrenic nerve, and epicardial fat. This review explores the indications, techniques, complications, and outcomes of epicardial ablation in patients with nonischemic cardiomyopathy. Although epicardial ablation adds to the complexity and risk of the ablation procedure, it is a vital tool that, combined with endocardial mapping and ablation, improves outcomes in patients with nonischemic cardiomyopathy suffering from ventricular arrhythmias.
Topics: Cardiac Imaging Techniques; Catheter Ablation; Epicardial Mapping; Humans; Pericardium; Tachycardia, Ventricular
PubMed: 32771186
DOI: 10.1016/j.ccep.2020.05.004 -
Journal of Cell Science Nov 2022The intestine, a rapidly self-renewing organ, is part of the gastrointestinal system. Its major roles are to absorb food-derived nutrients and water, process waste and...
The intestine, a rapidly self-renewing organ, is part of the gastrointestinal system. Its major roles are to absorb food-derived nutrients and water, process waste and act as a barrier against potentially harmful substances. Here, we will give a brief overview of the primary functions of the intestine, its structure and the luminal gradients along its length. We will discuss the dynamics of the intestinal epithelium, its turnover, and the maintenance of homeostasis. Finally, we will focus on the characteristics and functions of intestinal mesenchymal and immune cells. In this Cell Science at a Glance article and the accompanying poster, we aim to present the most recent information about gut cell biology and physiology, providing a resource for further exploration.
Topics: Homeostasis; Intestinal Mucosa; Nutrients
PubMed: 36349897
DOI: 10.1242/jcs.260248 -
Magyar Sebeszet Nov 2021Introduction: Not only atraumatic surgical technique, precise bleeding control, removal foreign materials from the abdomen, but also avoiding desiccation or mechanical... (Review)
Review
Introduction: Not only atraumatic surgical technique, precise bleeding control, removal foreign materials from the abdomen, but also avoiding desiccation or mechanical damage of peritoneal surface at abdominal surgery mean today evidence based expectation. Peritoneum with its extensive surface and special histological structure represents an important factor in normal physiological processes, furthermore as “Guard of abdomen” it has an important role to localise inflammatory reactions, useful as dialysing surface and provides also possibility for hyperthermic abdominal chemotherapy in tumour treatment. Largest part of peritoneal sac covers small intestine and colon. To prevent postoperative complications it is necessary to avoid desiccation of intestinal tract at laparoscopic and at open procedures as well – consequently “rehyration” is a routine recommendation today. Desiccation of intestinal tract results postoperative adhesions, furthermore damage of serosa will increase permeability of intestine wall and can result perforation. All the surgical recommendations suggest keeping intestine moist, whereas there are only a few real studies in surgical literature to support or to deny this theory. Our study reviews the pathophysiological and surgical respects of this situation and summarizes the results of latest researches of combined functions of peritoneum.
Topics: Humans; Laparoscopy; Peritoneum; Postoperative Complications
PubMed: 34821584
DOI: 10.1556/1046.74.2021.4.7 -
Journal of Morphology Jul 2021The avian yolk sac is a multifunctional extraembryonic organ that serves not only as a site of nutrient (yolk) absorption, but also for early hemopoiesis, and formation... (Review)
Review
The avian yolk sac is a multifunctional extraembryonic organ that serves not only as a site of nutrient (yolk) absorption, but also for early hemopoiesis, and formation of blood vessels. Although the yolk sac membrane being specialized to function as an extraembryonic absorptive organ, it is neither morphologically nor functionally part of the embryonic gut. Yolk absorption is by the phagocytic activity of the extraembryonic endoderm. I used cryohistology and resin embedding histology of complete developmental series of Japanese quail to document the development of the avian yolk sac and changes of the microscopic anatomy throughout development. This material is complemented by complete series of MRT-scans of live ostrich embryos from beginning of incubation through hatching. Considerable changes of size and shape of the yolk mass are documented and discussed as resulting from water flux from albumen to yolk associated with the biochemical activation of yolk sac proteins. During embryogenesis, the yolk sac endoderm forms villi that increase the absorptive surface and reach into the yolk ball. The histology of the absorptive epithelium is specialized for phagocytic absorption of yolk. During early developmental stages, the extraembryonic endoderm is single layered, but it eventually becomes several layers thick during later stages. The extraembryonic mesoderm forms an extensive layer of hematopoietic tissue; deep in this tissue lie the yolk sac vessels. During late stages of development, the erythropoietic tissue disappears, blood vessels are obliterated, and the yolk sac epithelium becomes apoptotic. Results are discussed in the light of the evolutionary history and phylogeny of the amniote egg.
Topics: Animals; Coturnix; Embryonic Development; Endoderm; Mesoderm; Yolk Sac
PubMed: 32930439
DOI: 10.1002/jmor.21262 -
Biochimica Et Biophysica Acta.... Aug 2023Membrane trafficking is essential to maintain the spatiotemporal control of protein and lipid distribution within membrane systems of eukaryotic cells. To achieve their... (Review)
Review
Membrane trafficking is essential to maintain the spatiotemporal control of protein and lipid distribution within membrane systems of eukaryotic cells. To achieve their functional destination proteins are sorted and transported into lipid carriers that construct the secretory and endocytic pathways. It is an emerging theme that lipid diversity might exist in part to ensure the homeostasis of these pathways. Sphingolipids, a chemical diverse type of lipids with special physicochemical characteristics have been implicated in the selective transport of proteins. In this review, we will discuss current knowledge about how sphingolipids modulate protein trafficking through the endomembrane systems to guarantee that proteins reach their functional destination and the proposed underlying mechanisms.
Topics: Sphingolipids; Biological Transport; Protein Transport; Membranes
PubMed: 37201864
DOI: 10.1016/j.bbalip.2023.159334 -
Journal of the American Society of... Nov 2021Autoantibodies binding to podocyte antigens cause idiopathic membranous glomerulonephritis (iMGN). However, it remains elusive how autoantibodies reach the subepithelial...
BACKGROUND
Autoantibodies binding to podocyte antigens cause idiopathic membranous glomerulonephritis (iMGN). However, it remains elusive how autoantibodies reach the subepithelial space because the glomerular filtration barrier (GFB) is size selective and almost impermeable for antibodies.
METHODS
Kidney biopsies from patients with iMGN, cell culture, zebrafish, and mouse models were used to investigate the role of nephronectin (NPNT) regulating microRNAs (miRs) for the GFB.
RESULTS
Glomerular endothelial cell (GEC)-derived miR-192-5p and podocyte-derived miR-378a-3p are upregulated in urine and glomeruli of patients with iMGN, whereas glomerular NPNT is reduced. Overexpression of miR-192-5p and morpholino-mediated npnt knockdown induced edema, proteinuria, and podocyte effacement similar to podocyte-derived miR-378a-3p in zebrafish. Structural changes of the glomerular basement membrane (GBM) with increased lucidity, splitting, and lamellation, especially of the lamina rara interna, similar to ultrastructural findings seen in advanced stages of iMGN, were found. IgG-size nanoparticles accumulated in lucidity areas of the lamina rara interna and lamina densa of the GBM in npnt-knockdown zebrafish models. Loss of slit diaphragm proteins and severe structural impairment of the GBM were further confirmed in podocyte-specific Npnt knockout mice. GECs downregulate podocyte NPNT by transfer of miR-192-5p-containing exosomes in a paracrine manner.
CONCLUSIONS
Podocyte NPNT is important for proper glomerular filter function and GBM structure and is regulated by GEC-derived miR-192-5p and podocyte-derived miR-378a-3p. We hypothesize that loss of NPNT in the GBM is an important part of the initial pathophysiology of iMGN and enables autoantigenicity of podocyte antigens and subepithelial immune complex deposition in iMGN.
Topics: Animals; Antigen-Antibody Complex; Autoantigens; Cells, Cultured; Coculture Techniques; Endothelial Cells; Exosomes; Extracellular Matrix Proteins; Gene Expression Regulation; Gene Targeting; Glomerular Basement Membrane; Glomerulonephritis, Membranous; Gold Sodium Thiosulfate; Humans; Kidney Glomerulus; Metal Nanoparticles; Mice; MicroRNAs; Paracrine Communication; Permeability; Podocytes; Proteinuria; Transfection; Zebrafish; Zebrafish Proteins
PubMed: 34716242
DOI: 10.1681/ASN.2020121699