Association of Src-family protein tyrosine kinases with sphingolipids in rat cerebellar granule cells differentiated in culture

Src family kinases play a relevant role in the development and differentiat ion of neuronal cells. They are abundant in sphingolipid-enriched membrane domains of many cell types, and these domains are hypothesized to function in bringing together molecules important to signal transduction. We studied the association of Src family tyrosine kinases and their negative regulato ry kinase, Csk, with sphingolipids in sphingolipid-enriched domains of rat cerebellar granule cells differentiated in culture. We find that c-Src, Lyn and Csk are enriched in the sphingolipid-enriched fraction prepared from t hese cells. Coimmunoprecipitation experiments show that these and sphingoli pids are part of the same domain. Cross-linking experiments with a photoact ivable, radioactive GD1b derivative show that c-Src and Lyn, which are anch ored to the membrane via a myristoyl chain, associate directly with GD1b. C sk, which is not inserted in the hydrophobic core of the membrane, is not p hotolabeled by this ganglioside. These results suggest that lipid-lipid, li pid-protein, and protein-protein interactions cooperate to maintain domain structure. We hypothesize that such interactions might play a role in the p rocess of neuronal differentiation.