Effect of membrane-interacting amphiphiles on association of membrane glycoproteins with assembled cytoskeletal proteins in concanavalin A-activated rabbit platelets.

Membrane-interacting amphiphiles, lysophosphatidylcholine, cepharanthine and chlorpromazine, inhibited concanavalin A (Con A)-induced platelet activation in a dose-dependent manner, as judged by the inhibition of serotonin release. These amphiphiles did not influence the binding of Con A to surface membrane glycoproteins. Marked increase in the amount of the cytoskeletal proteins, myosin, actin and actin-binding protein, in the Triton-insoluble residue of the Con A-activated platelets, as well as in the surface membrane glycoproteins with molecular weights of 224,000, 201,000, 119,000 and 92,000 found in the same residue, was inhibited by any of the three amphiphiles in a dose-dependent manner. Such inhibitory effect, however, was abolished when the amphiphiles were washed out from the platelets before the activation. These findings suggest that these membrane-interacting amphiphiles may inhibit the Con A-induced assembly of the cytoskeletal proteins and their association with surface membrane glycoproteins, probably by physically altering the membrane properties.