scholarly journals Transient Effect of Calcium Influx on PIP2 Clusters in the Inner Plasma Membrane Leaflet of Intact Cells

2016 ◽  
Vol 110 (3) ◽  
pp. 204a
Author(s):  
Weixiang Jin ◽  
Arnd Pralle
Keyword(s):  
Plasma Membrane ◽  
Calcium Influx ◽  
Transient Effect ◽  
Intact Cells

scholarly journals Plasma membrane integrity in health and disease: significance and therapeutic potential

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Catarina Dias ◽  
Jesper Nylandsted
Keyword(s):  
Plasma Membrane ◽  
Therapeutic Potential ◽  
Calcium Influx ◽  
Membrane Integrity ◽  
Cell Types ◽  
Physical Parameters ◽  
Membrane Repair ◽  
Plasma Membrane Integrity ◽  
Repair Mechanisms ◽  
And Function

AbstractMaintenance of plasma membrane integrity is essential for normal cell viability and function. Thus, robust membrane repair mechanisms have evolved to counteract the eminent threat of a torn plasma membrane. Different repair mechanisms and the bio-physical parameters required for efficient repair are now emerging from different research groups. However, less is known about when these mechanisms come into play. This review focuses on the existence of membrane disruptions and repair mechanisms in both physiological and pathological conditions, and across multiple cell types, albeit to different degrees. Fundamentally, irrespective of the source of membrane disruption, aberrant calcium influx is the common stimulus that activates the membrane repair response. Inadequate repair responses can tip the balance between physiology and pathology, highlighting the significance of plasma membrane integrity. For example, an over-activated repair response can promote cancer invasion, while the inability to efficiently repair membrane can drive neurodegeneration and muscular dystrophies. The interdisciplinary view explored here emphasises the widespread potential of targeting plasma membrane repair mechanisms for therapeutic purposes.

scholarly journals Fluorescent, short-chain C6-NBD-sphingomyelin, but not C6-NBD-glucosylceramide, is subject to extensive degradation in the plasma membrane: implications for signal transduction related to cell differentiation

1995 ◽  
Vol 309 (3) ◽  
pp. 905-912 ◽  
Author(s):  
J W Kok ◽  
T Babia ◽  
K Klappe ◽  
D Hoekstra
Keyword(s):  
Signal Transduction ◽  
Plasma Membrane ◽  
Cell Differentiation ◽  
Plasma Membranes ◽  
Cell Types ◽  
Short Chain ◽  
Synthetic Activity ◽  
Intact Cells ◽  
Ht29 Cells ◽  
Extensive Degradation

The involvement of the plasma membrane in the metabolism of the sphingolipids sphingomyelin (SM) and glucosylceramide (GlcCer) was studied, employing fluorescent short-chain analogues of these lipids, 6-[N-(7-nitro-2,1,3-benzoxadiazol-4-yl) amino]hexanoylsphingosylphosphorylcholine (C6-NBD-SM), C6-NBD-GlcCer and their common biosynthetic precursor C6-NBD-ceramide (C6-NBD-Cer). Although these fluorescent short-chain analogues are metabolically active, some caution is to be taken in view of potential changes in biophysical/biochemical properties of the lipid compared with its natural counterpart. However, these short-chain analogues offer the advantage of studying the lipid metabolic enzymes in their natural environment, since detergent solubilization is not necessary for measuring their activity. These studies were carried out with several cell types, including two phenotypes (differing in state of differentiation) of HT29 cells. Degradation and biosynthesis of C6-NBD-SM and C6-NBD-GlcCer were determined in intact cells, in their isolated plasma membranes, and in plasma membranes isolated from rat liver tissue. C6-NBD-SM was found to be subject to extensive degradation in the plasma membrane, due to neutral sphingomyelinase (N-SMase) activity. The extent of C6-NBD-SM hydrolysis showed a general cell-type dependence and turned out to be dependent on the state of cell differentiation, as revealed for HT29 cells. In undifferentiated HT29 cells N-SMase activity was at least threefold higher than in its differentiated counterpart. In contrast, in all cell types studied, very little if any biosynthesis of C6-NBD-SM from the precursor C6-NBD-Cer occurred. Moreover, in the case of C6-NBD-GlcCer, neither hydrolytic nor synthetic activity was found to be associated with the plasma membrane. These results are discussed in the context of the involvement of the sphingolipids SM and GlcCer in signal transduction pathways in the plasma membrane.

scholarly journals N-glycosylation critically regulates function of oxalate transporter SLC26A6

2016 ◽  
Vol 311 (6) ◽  
pp. C866-C873 ◽  
Author(s):  
R. Brent Thomson ◽  
Claire L. Thomson ◽  
Peter S. Aronson
Keyword(s):  
Plasma Membrane ◽  
Intestinal Secretion ◽  
Integral Membrane Proteins ◽  
Extracellular Loop ◽  
Transport Activity ◽  
Intact Cells ◽  
Functional Studies ◽  
And Function ◽  
Oxalate Transport

The brush border Cl−-oxalate exchanger SLC26A6 plays an essential role in mediating intestinal secretion of oxalate and is crucial for the maintenance of oxalate homeostasis and the prevention of hyperoxaluria and calcium oxalate nephrolithiasis. Previous in vitro studies have suggested that SLC26A6 is heavily N-glycosylated. N-linked glycosylation is known to critically affect folding, trafficking, and function in a wide variety of integral membrane proteins and could therefore potentially have a critical impact on SLC26A6 function and subsequent oxalate homeostasis. Through a series of enzymatic deglycosylation studies we confirmed that endogenously expressed mouse and human SLC26A6 are indeed glycosylated, that the oligosaccharides are principally attached via N-glycosidic linkage, and that there are tissue-specific differences in glycosylation. In vitro cell culture experiments were then used to elucidate the functional significance of the addition of the carbohydrate moieties. Biotinylation studies of SLC26A6 glycosylation mutants indicated that glycosylation is not essential for cell surface delivery of SLC26A6 but suggested that it may affect the efficacy with which it is trafficked and maintained in the plasma membrane. Functional studies of transfected SLC26A6 demonstrated that glycosylation at two sites in the putative second extracellular loop of SLC26A6 is critically important for chloride-dependent oxalate transport and that enzymatic deglycosylation of SLC26A6 expressed on the plasma membrane of intact cells strongly reduced oxalate transport activity. Taken together, these studies indicated that oxalate transport function of SLC26A6 is critically dependent on glycosylation and that exoglycosidase-mediated deglycosylation of SLC26A6 has the capacity to profoundly modulate SLC26A6 function.

Stimulation of calcium influx by platelet activating factor in Dictyostelium

1995 ◽  
Vol 108 (4) ◽  
pp. 1597-1603
Author(s):  
R. Schaloske ◽  
C. Sordano ◽  
S. Bozzaro ◽  
D. Malchow
Keyword(s):  
Plasma Membrane ◽  
G Protein ◽  
Dictyostelium Discoideum ◽  
Calcium Influx ◽  
Platelet Activating Factor ◽  
Inactive Compound ◽  
Time Period ◽  
Dependent Pathway ◽  
Stimulation Of

Platelet activating factor (PAF) induces Ca2+ influx in Dictyostelium discoideum. In this investigation we used this activity to analyze the mechanism of PAF action. We found that PAF activity was confined to the period of spike-shaped oscillations and suggest that the role of PAF is to augment cAMP relay. PAF seems to act only a few times during this time period of two hours, since Ca2+ entry adapted to a subsequent stimulus for about 30 minutes. PAF showed a reduced response in the G protein beta- strain LW14 and was unable to induce Ca2+ influx in the G alpha 2- strains HC85 and JM1. The latter expresses the cAMP receptors cAR1 constitutively, and exhibits cAMP-induced Ca2+ influx, albeit at a reduced level. In order to decide whether the inability of PAF to elicit a Ca2+ response in JM1 cells was due to the lack of differentiation and/or the lack of G alpha 2, we inhibited the IP3-dependent pathway with compound U73122 and found that Ca2+ entry was blocked, whereas a closely related inactive compound, U73343, did not alter the response. In agreement with this, NBD-Cl, an inhibitor of Ca2+ uptake into the IP3-sensitive store in Dictyostelium, also abolished PAF activity. The latter was not inhibited by the plasma membrane antagonists BN-52021 or WEB 2170. Therefore PAF seems to operate intracellularly via the IP3-signalling pathway at or upstream of the IP3-sensitive store.

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