scholarly journals Phosphorylation of Nephrin induces phase separated domains that move through actomyosin contraction

2019 ◽  
Author(s):  
Soyeon Kim ◽  
Joseph M. Kalappurakkal ◽  
Satyajit Mayor ◽  
Michael K. Rosen
Keyword(s):  
Plasma Membrane ◽  
Actin Cytoskeleton ◽  
Cell Periphery ◽  
Actin Assembly ◽  
Regulatory Pathway ◽  
Basal Plasma Membrane ◽  
Basal Plasma ◽  
Multivalent Interactions ◽  
And Control ◽  
Actomyosin Contraction

AbstractThe plasma membrane of eukaryotic cells is organized into lipid and protein microdomains, whose assembly mechanisms and functions are incompletely understood. We demonstrate that proteins in the Nephrin/Nck/N-WASP actin-regulatory pathway cluster into micron-scale domains at the basal plasma membrane upon triggered phosphorylation of transmembrane Nephrin. The domains are persistent but readily exchange components with their surroundings, and their formation is dependent on the number of Nck SH3 domains, suggesting they are phase separated polymers assembled through multivalent interactions among the three proteins. The domains form independent of the actin cytoskeleton, but acto-myosin contractility induces their rapid lateral movement. Nephrin phosphorylation induces larger clusters at the cell periphery, which are associated with extensive actin assembly and dense filopodia. Our studies illustrate how multivalent interactions between proteins at the plasma membrane can produce micron-scale organization of signaling molecules, and how the resulting clusters can both respond to and control the actin cytoskeleton.

scholarly journals Phosphorylation of nephrin induces phase separated domains that move through actomyosin contraction

2019 ◽  
Vol 30 (24) ◽  
pp. 2996-3012 ◽  
Author(s):  
Soyeon Kim ◽  
Joseph M. Kalappurakkal ◽  
Satyajit Mayor ◽  
Michael K. Rosen
Keyword(s):  
Plasma Membrane ◽  
Actin Cytoskeleton ◽  
Transmembrane Protein ◽  
Cell Periphery ◽  
Actin Assembly ◽  
Basal Plasma Membrane ◽  
Basal Plasma ◽  
Multivalent Interactions ◽  
And Control ◽  
Actomyosin Contraction

The plasma membrane of eukaryotic cells is organized into lipid and protein microdomains, whose assembly mechanisms and functions are incompletely understood. We demonstrate that proteins in the nephrin/Nck/N-WASP actin-regulatory pathway cluster into micron-scale domains at the basal plasma membrane upon triggered phosphorylation of transmembrane protein nephrin. The domains are persistent but readily exchange components with their surroundings, and their formation is dependent on the number of Nck SH3 domains, suggesting they are phase separated polymers assembled through multivalent interactions among the three proteins. The domains form independent of the actin cytoskeleton, but acto-myosin contractility induces their rapid lateral movement. Nephrin phosphorylation induces larger clusters at the cell periphery, which are associated with extensive actin assembly and dense filopodia. Our studies illustrate how multivalent interactions between proteins at the plasma membrane can produce micron-scale organization of signaling molecules, and how the resulting clusters can both respond to and control the actin cytoskeleton.

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.

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