Effect of membrane lipid composition and microtubule structure on lectin interactions of mouse lm cells

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Abstract
Concanavalin A (Con A) binding and Con A‐mediated hemadsorption to LM cells were found to decrease significantly at both 5–7°C and 15–19°C. The higher of these critical temperatures responds to a change in state of the membrane lipids and can be increased or decreased in cells where the membrane phospholipids contain less or more double bonds, respectively. The lower critical temperature for Con A binding or Con A‐mediated hemadsorption does not respond to these changes in membrane lipid composition. Though the amount of Con A bound to the cell surface is a determinant of Con A‐mediated agglutinability, the major components of the decreases in Con A‐mediated hemadsorption which occur at both these critical temperatures do not have their origin in the decreases in Con A binding which occur over these same temperature ranges – that is 5–7°C and 15–19°C.Con A‐mediated hemadsorption measured at 22°C was dramatically inhibited when LM cells were first incubated at 7°C or less. Reversal of this inhibition required 20–30 min of subsequent incubation at 22°C, indicating that factors other than membrane lipid “fluidity” are determinants of agglutinability. LM cells treated with the microtubule‐disrupting alkaloids colchicine, colcemid, or vinblastine at concentrations as low as 10−6 M were as much as fourfold more agglutinable with Con A. By contrast, lumicolchicine, an inactive derivative of colchicine, had a slight inhibitory effect on Con A‐mediated hemadsorption. Colchicine, vinblastine, or lumicolchicine treatment of LM cells did not alter the quantitative binding of labeled lectin. The results suggest that membrane lipid “fluidity” and the cell cytoskeleton (microtubule/microfilament system) are important determinants of lectin interactions with cell surfaces. The results are interpreted in terms of a model of cell–cell and cell–lectin interactions which assigns a central role to the Con A receptor.