Restoration of adhesive potentials of Ehrlich ascites carcinoma cells by modification of plasma membrane

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Abstract
A novel technique for modulating the spreading of ascites cells has been developed. Plasma membranes of Ehrlich ascites carcinoma cells were modified in two different ways: 1) biotin residues were covalently coupled to membrane components; 2) biotinylated lipid was introduced into plasma membranes. Adhesion and spreading of modified cells on avidin‐coated substrates were studied and compared to those of non‐modified cells. Both types of membrane alteration were shown to induce specific (biotin‐dependent) interaction with immobilized avidin with resultant cell spreading. Spread cells attained epithelioid‐like morphology with the formation of wide thin lamellae, focal contacts with substrate, and circular actin bundles. The process of spreading was shown to be energy‐dependent: it could be blocked by metabolic inhibitors and by low temperature. Formation of extended lamellae was prevented by preincubation of cells in the presence of cytochalasin B. The effects of metabolic poisons, low temperature, and microfilament–disruptive drugs were reversible and after the restoration of physiological conditions the cells resumed the spreading process. Immunoprecipitation of biotinylated cell lysates with antiserum to cytoplasmic domain of 3,‐integrin subunit revealed a major 110 kD avidin‐binding component. We conclude that lack of spreading of ascites carcinoma cells may be explained by the lack of functionally active adhesion‐ and spreading‐competent cell‐surface receptors, but may not be attributed to the defects in intracellular function or organization. Intracellular machinery of cell spreading is preserved in these ascites cells and could be turned on by cell attachment to the substrate via artificial adhesive site incorporated into plasma membrane.