Lipid Bilayer Of Plasma Membrane Research Articles

Structural changes in BHK cell plasma membrane caused by the binding of vesicular stomatitis virus

Spin label electron spin resonance techniques using a nitroxide derivative of stearic acid were used to detect changes in plasma membrane structure caused by the binding of vesicular stomatitis virus (VSV) to cell plasma membranes of intact BHK-21 cells. The results indicate that binding of VSV to cell surface receptors causes an increase in the observed rigidity of the plasma membrane lipid bilayer. This change in membrane structure, which appears to be caused by the cross-linking of receptors in the plane of the plasma membrane, could be prevented by treating the cells with colchicine before addition of virus and could be reversed by treating the cells with colchicine after addition of virus. Cells treated with a monovalent, water-soluble derivative of VSV G-protein (Gs) did not show an increase in plasma membrane bilayer rigidity. However, addition of anti-VSV G-protein immunoglobulin G to cells pretreated with G8 caused an increase in plasma membrane bilayer rigidity. This increased rigidity could also be reversed by the addition of colchicine. Fluorescence microscopy was used to determine the distribution of fluorescein-labeled VSV particles on the cell surface after addition of virus. Approximately 30 min after addition of virus, discrete areas on the cell surface showed fluorescent staining, which coalesced to apical regions of the cell after approximately 40 min.

The possible role of intracellular receptors in the expression of narcotic antagonist precipitated abstinence

The antagonist potencies of methylnaloxone and naloxone were measured for morphine in the isolated guinea pig ileum by the pA 2 method and a potency ratio determined. A second potency ratio was determined by comparing the concentration of each antagonist required to produce abstinence-like contractures of ileal tissues from morphine-treated guinea pigs. If the latter response required penetration of the cell membrane lipid bilayer, one would expect methylnaloxone, a quaternary amine, to be significantly less potent than naloxone. Comparison of potency ratios for methylnaloxone and naloxone did not support this hypothesis.

Beta-interferon-induced time-dependent changes in the plasma membrane lipid bilayer of cultured cells.

The time-dependent interferon-induced structural changes in the plasma membrane lipid bilayer have been investigated in cultured cells using spin label electron spin resonance techniques. Treatment of human HeLa-S3 cells in suspension culture with human beta 1 interferon (640 u/ml) for as short a time as 30 min causes an increase in the rigidity of the plasma membrane lipid bilayer (Landsberger, Pfeffer and Tamm, in preparation). The plasma membrane rigidity of interferon-treated cells returns to the level of control cells within 3 to 5 hr, but by 24 hr after beginning of treatment, the rigidity of the plasma membrane is increased again and remains so for at least 2 days. Mouse beta interferon causes both an early (Landsberger, Pfeffer and Tamm, in preparation) and a late increase in membrane rigidity in homologous mouse L-929 cells, but not in heterologous HeLa-S3 cells. Thus, the interferon-induced perturbation of membrane structure is species specific. The late increase in membrane rigidity may have a different underlying mechanism from that of the early increase. While the early and transient change probably is related to signal generation and transmission, the later and persistent change may be an aspect of the phenotype and interferon-treated cells and may reflect changes in the plasma membrane-cytoskeletal complex.

Interaction of lipids with the plasma membrane of sperm cells. I. The antifertilization action of cholesterol.

The inhibitory action of cholesterol-containing suspensions on fertilizing capacity in uterine-capacitated rabbit sperm cells showed a direct dependence on the concentration of sterol. Dispersion with synthetic phosphatidylcholine as a nonsonicated suspension or as liposomes did not alter this antifertilization effect. Esterification of the sterol, however, caused a complete loss of inhibitory activity. Cholesterol inhibited induction of the acrosome reaction among epididymal rat spermatozoa incubated under chemically defined conditions. Other agents with a negative effect on the acrosome reaction were seminal plasma membrane vesicles and palmitic acid. Egg lecithin-liposomes and bovine serum albumin, especially after being delipidated, facilitated it. These results corroborate the viewpoint that changes in the lipid bilayer of sperm plasma membrane significantly influence fertilizing capacity among mammalian spermatozoa.

The distribution of spectrin along the membranes of normal and echinocytic human erythrocytes.

Spectrin molecules are distributed uniformly throughout the submembranous regions of intact human erythrocytes. Spectrin does not appear to extend into the red blood cell cytoplasm to any significant extent. Thus, it does not form a recognizable internal scaffolding nor does it seem to connect distant segments of the cell membrane. Spectrin retains its submembranous location in the spiny processes of echinocytes produced by ATP depletion. Thus, these processes do not seem to form by a simple extrusion mechanism powered by contraction of the spectrin network. Spectrin seems to be important for the stability of the lipid bilayer of the red cell membrane, and it probably also plays a role in regulating red cell shape. How it performs either function is still unknown.

Introduction of antigenic phospholipids into the plasma membrane of mammalian cells: organization and antibody-induced lipid redistribution.

Phosphatidylethanolamine bearing the 2,4,6-trinitrophenyl hapten was introduced into the surface membrane of mammalian fibroblasts by incubating the cells with small unilamellar vesicles containing this hapten-conjugated lipid. Consistent with integration of the antigen into the plasma membrane lipid bilayer, the exogenously supplied lipid was observed by immunofluorescence to diffuse rapidly (D greater than or equal to 0.6 X 10(-8) cm2/sec) over the surface of polykaryons formed between vesicle- and non-vesicle-treated cells. Association of the exogenous lipids with cells via adsorption of vesicles to the plasma membrane was rigorously excluded by a combination of ultrastructural and immunofluorescence studies. The distribution of the integrated antigenic lipid in the plasma membranes of vesicle-treated cells was followed by immunofluorescence microscopy. The exogenously supplied hapten-conjugated phospholipid was observed to be uniformly distributed and remained so for up to 1 hr at 37 degrees C. However, upon the addition of bivalent, but not monovalent, antihapten antibodies, the phospholipid underwent a rapid temperature-dependent redistribution, forming small patches that eventually coalesced into one or more large aggregates. This unexpected finding is discussed in terms of the mode of insertion of the lipid into the cell surface and the possible mechanisms by which bivalent ligands might alter the mobility and distribution of cell surface phospholipids.

Orientation of cell-surface antigens in the lipid bilayer of lymphocyte plasma membrane.

Human HLA-A, B, C and Ia antigens were labelled by lactoperoxidase-catalysed iodination of the inner surface of lymphocyte plasma membrane and thus are transmembrane proteins. In contrast, membrane-bound human IgM and mouse IgM, IgD and Thy-1 antigen were not labelled on the inner membrane surface.

Distribution of cholesterol between the outer and inner halves of the lipid bilayer of mycoplasma cell membranes

Rapid kinetic studies of filipin binding to intact cells and isolated membranes were performed with a stopped-flow apparatus to determine the distribution of cholesterol in the outer and inner surfaces of mycoplasma membranes. The initial rates of association of filipin with cholesterol in Mycoplasma gallisepticum and Mycoplasma capricolum intact cells were slower than those obtained with isolated membrane preparations. Ratios of the second-order rate constants for filipin binding to cells relative to membranes indicate that cholesterol is distributed symmetrically in membranes of M. gallisepticum cells whereas in M. capricolum ∼66% of the free cholesterol is localized in the outer half of the lipid bilayer.