scholarly journals TMEM16F and dynamins control expansive plasma membrane reservoirs

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Christine Deisl ◽  
Donald W. Hilgemann ◽  
Ruhma Syeda ◽  
Michael Fine
Keyword(s):  
Plasma Membrane ◽  
Neutral Lipids ◽  
Lipid Binding ◽  
Cell Swelling ◽  
Mechanosensitive Channels ◽  
Membrane Stress ◽  
Anionic Phospholipids ◽  
Basal Plasma Membrane ◽  
Basal Plasma ◽  
Phospholipid Scrambling

AbstractCells can expand their plasma membrane laterally by unfolding membrane undulations and by exocytosis. Here, we describe a third mechanism involving invaginations held shut by the membrane adapter, dynamin. Compartments open when Ca activates the lipid scramblase, TMEM16F, anionic phospholipids escape from the cytoplasmic monolayer in exchange for neutral lipids, and dynamins relax. Deletion of TMEM16F or dynamins blocks expansion, with loss of dynamin expression generating a maximally expanded basal plasma membrane state. Re-expression of dynamin2 or its GTPase-inactivated mutant, but not a lipid binding mutant, regenerates reserve compartments and rescues expansion. Dynamin2-GFP fusion proteins form punctae that rapidly dissipate from these compartments during TMEM16F activation. Newly exposed compartments extend deeply into the cytoplasm, lack numerous organellar markers, and remain closure-competent for many seconds. Without Ca, compartments open slowly when dynamins are sequestered by cytoplasmic dynamin antibodies or when scrambling is mimicked by neutralizing anionic phospholipids and supplementing neutral lipids. Activation of Ca-permeable mechanosensitive channels via cell swelling or channel agonists opens the compartments in parallel with phospholipid scrambling. Thus, dynamins and TMEM16F control large plasma membrane reserves that open in response to lateral membrane stress and Ca influx.

Initiation of HeLa cell adhesion to collagen is dependent upon collagen receptor upregulation, segregation to the basal plasma membrane, clustering and binding to the cytoskeleton

1992 ◽  
Vol 101 (4) ◽  
pp. 873-883
Author(s):  
M.L. Lu ◽  
R.J. McCarron ◽  
B.S. Jacobson
Keyword(s):  
Plasma Membrane ◽  
Cell Attachment ◽  
Cell Spreading ◽  
Threshold Effect ◽  
Type I ◽  
Receptor Clustering ◽  
Collagen Receptors ◽  
Basal Plasma Membrane ◽  
Basal Plasma ◽  
Collagen Receptor

It was recently reported that HeLa cells have three Arg-Gly-Asp-dependent collagen receptors that do not appear to be in the integrin family of extracellular matrix receptors and bind to either type I or IV collagen or to type I gelatin. It was our goal to determine how these receptors function in HeLa cell-substratum adhesion. We report here that the sequence of events by which the receptors mediate adhesion to collagen or gelatin is: (1) induction of cell attachment by specific collagen receptor-substratum interactions with culture dishes covalently coated with either type I collagen or gelatin - attachment is inhibited by soluble gelatin; (2) stabilization of attachment by exocytotic upregulation of the receptors to the basal plasma membrane, which was demonstrated by analyzing, during cell adhesion, the redistribution of the collagen receptors among the apical plasma membrane exposed to the culture medium, the basal plasma membrane contacting the culture dish, and an intracellular pool of plasma membrane vesicles; (3) the initiation of cell spreading by receptor clustering and cytoskeletal association. Cell spreading is a threshold effect with regard to the surface concentration of gelatin, indicating that collagen receptor clustering is a precondition to the onset of spreading. Observations consistent with this interpretation of the threshold effect are that cells attach but spread more slowly on a substratum that retards receptor clustering, and that collagen receptors, when viewed by immunofluorescence microscopy, form a punctate pattern of fluorescence in the basal plasma membrane during cell spreading. It is also shown that more collagen receptors co-isolate with nondenaturing detergent-stable cytoskeletal preparations after the collagen receptors have been either clustered by antibodies or gelatin in solution, or by a collagen matrix. This indicates that clustering drives the receptors to bind to the cytoskeleton and is a necessary step in the transition from cell attachment to cell spreading.

A transmission electron microscopical study of the tegument of Maritrema feliui (Digenea: Microphallidae)

2013 ◽  
Vol 58 (4) ◽  
Author(s):  
Zdzisław Świderski ◽  
Isabel Montoliu ◽  
Carlos Feliu ◽  
David Gibson ◽  
Jordi Miquel
Keyword(s):  
Surface Layer ◽  
Plasma Membrane ◽  
Outer Layer ◽  
Microscopical Study ◽  
The Other ◽  
Cytoplasmic Region ◽  
Transmission Electron ◽  
Basal Plasma Membrane ◽  
Basal Plasma ◽  
Electron Microscopical

AbstractThe tegument of the microphallid digenean Maritrema feliui, examined by means of TEM, is described as a syncytial epithelium organised into two layers. The outer layer is an external anucleate, cytoplasmic region connected to a second region composed of nucleate perikarya (cytons) deeply embedded in the surrounding cortical parenchyma. The surface layer of the tegument is covered by a plasma membrane with many deep invaginations, which are apparently pinocytotic. This layer also bears numerous large, electron-dense spines of two types, which are intracellular and attached to the basal plasma membrane. Its cytoplasm is rich in free ribosomes, contains numerous mitochondria, disc-shaped granules frequently arranged in a rouleau, and several large, moderately electron-dense, membranous bodies. The subtegumentary perikarya and their nuclei, which are both flattened, are described in detail, as are their connections with the surface tegument. These perikarya appear to be the source of the disc-shaped granules and some of the other inclusions present in the surface layer. The main characteristics of the tegumental structure of M. feliui are commented upon in relation to the findings of previous publications and their suggested functions.

scholarly journals Insulin Stimulates GLUT4 Trafficking to the Syncytiotrophoblast Basal Plasma Membrane in the Human Placenta

2019 ◽  
Vol 104 (9) ◽  
pp. 4225-4238 ◽  
Author(s):  
Laura B James-Allan ◽  
Jaron Arbet ◽  
Stephanie B Teal ◽  
Theresa L Powell ◽  
Thomas Jansson
Keyword(s):  
Plasma Membrane ◽  
Protein Expression ◽  
Membrane Trafficking ◽  
Human Placenta ◽  
Plasma Membranes ◽  
Glucose Transporter ◽  
Maternal Obesity ◽  
Normal Body Mass Index ◽  
Basal Plasma Membrane ◽  
Basal Plasma

AbstractContextPlacental transport capacity influences fetal glucose supply. The syncytiotrophoblast is the transporting epithelium in the human placenta, expressing glucose transporters (GLUTs) and insulin receptors (IRs) in its maternal-facing microvillous plasma membrane (MVM) and fetal-facing basal plasma membrane (BM).ObjectiveThe objectives of this study were to (i) determine the expression of the insulin-sensitive GLUT4 glucose transporter and IR in the syncytiotrophoblast plasma membranes across gestation in normal pregnancy and in pregnancies complicated by maternal obesity, and (ii) assess the effect of insulin on GLUT4 plasma membrane trafficking in human placental explants.Design, Setting, and ParticipantsPlacental tissue was collected across gestation from women with normal body mass index (BMI) and mothers with obesity with appropriate for gestational age and macrosomic infants. MVM and BM were isolated.Main Outcome MeasuresProtein expression of GLUT4, GLUT1, and IR were determined by western blot.ResultsGLUT4 was exclusively expressed in the BM, and IR was predominantly expressed in the MVM, with increasing expression across gestation. BM GLUT1 expression was increased and BM GLUT4 expression was decreased in women with obesity delivering macrosomic babies. In placental villous explants, incubation with insulin stimulated Akt (S473) phosphorylation (+76%, P = 0.0003, n = 13) independent of maternal BMI and increased BM GLUT4 protein expression (+77%, P = 0.0013, n = 7) in placentas from lean women but not women with obesity.ConclusionWe propose that maternal insulin stimulates placental glucose transport by promoting GLUT4 trafficking to the BM, which may enhance glucose transfer to the fetus in response to postprandial hyperinsulinemia in women with normal BMI.

Bicarbonate-induced activation of taurocholate transport across the basal plasma membrane of human term trophoblast

1991 ◽  
Vol 260 (6) ◽  
pp. G887-G894 ◽  
Author(s):  
M. Y. el-Mir ◽  
N. Eleno ◽  
M. A. Serrano ◽  
P. Bravo ◽  
J. J. Marin
Keyword(s):  
Plasma Membrane ◽  
Carbonic Anhydrase ◽  
Voltage Clamp ◽  
Anion Exchange ◽  
Coupling Ratio ◽  
Human Trophoblast ◽  
Carbonyl Cyanide ◽  
Basal Plasma Membrane ◽  
Basal Plasma ◽  
Taurocholate Transport

The efflux of [14C]taurocholate from previously loaded vesicles, obtained from basal plasma membrane of human trophoblast, was studied. Apparent Km (620 microM) and Vmax (1.79 nmol.min-1.mg protein-1) values were similar to those found in influx experiments (Marin et al., Gastroenterology 99: 1431-1438, 1990). Transmembrane gradients of both bicarbonate (100 mM) and unlabeled taurocholate (0.5 mM) accelerated [14C]taurocholate efflux. The bicarbonate-induced effect was not abolished by carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) and K(+)-valinomycin voltage clamp. Neither was it mimicked by 5,5'-dimethyloxazolidine 2,4-dione (DMO) or by other organic (taurine, glycine, lactate, or acetate) or inorganic (Cl-, SCN-, HPO24-, or SO24-) anions, and it was not sensitive to carbonic anhydrase inhibitors. No effect of bicarbonate was observed either in the absence of gradient or in the presence of a cis-directed gradient. Bicarbonate-induced transstimulation was related to an increase in the value for the apparent Vmax (+30%). Study of the stoichiometry suggests that the most probable coupling ratio is one, bicarbonate: taurocholate. In summary, these results provide evidence for the existence of a bicarbonate-driven anion exchange in the basal plasma membrane of the human term placental trophoblast.

Use of saponin in the preparation of brush border from a parasitic flatworm

1981 ◽  
Vol 59 (6) ◽  
pp. 911-917 ◽  
Author(s):  
M. S. Rahman ◽  
D. F. Mettrick ◽  
R. B. Podesta
Keyword(s):  
Electron Microscopy ◽  
Plasma Membrane ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Hymenolepis Diminuta ◽  
Parasitic Flatworm ◽  
Basal Plasma Membrane ◽  
Basal Plasma

Saponin treatment in hypotonic or hypertonic fluids, followed by vibration, was used to isolate the brush border membrane from the surface epithelial syncytium of Hymenolepis diminuta. Electron microscopy of the membrane pellets and the parasites indicated that the area of the syncytium sheered by vibration of the parasites was correlated with the areas of the syncytium in which there occurred the greatest amount of osmotically induced swelling: below and adjacent to the brush border in hypotonic incubation, and the infoldings of the basal plasma membrane of the syncytium in hypertonic incubations. Vesiculation of the microvilli occurred in incubations made hypertonic with mannitol.

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