Association of renal cell carcinoma antigen, disialylgalactosylgloboside, with c-Src and Rho A in clustered domains at the surface membrane

Disialylgalactosylgloboside (DSGG), defined by monoclonal antibody RM2, is a renal cell carcinoma (RCC)-associated antigen which mediates adhesion of RCC TOS-1 cells to certain lung tissue target cells. This adhesion process may initiate preferential lung metastasis of RCC. Ganglioside GM3 is a B16 melanoma-associated antigen which similarly adheres to target cells and pro motes consequent metastasis. In view of the close association of GM3-enrich ed microdomain with transducer molecules c-Src, Rho A, and FAK in B16 cells , we investigated the organizational status of DSGG in RCC cell line TOS-1, with the following results: i) DSGG, but not monosialylgalactosylgloboside , showed extensive clustering at the TOS-1 cell surface; ii) a low-density membrane fraction isolated from TOS-1 cells contained >95% of cellular DSGG , although protein content in this fraction was <1% of total cellular prote in; iii) this fraction contained c-Src, Rho A, and FAK, but not H-Ras; iv) c-Src and Rho A were co-immunoprecipitated with DSGG through anti-DSGG mAb RM2 (IgM) affixed to a column, These observations indicate that DSGG is clu stered in RCC, as typified by TOS-1 cells, to form a microdomain in which i t is closely associated with c-Src, Rho A, and FAK, and may constitute a fu nctional unit as has been observed for GM3 with transducer molecules in B16 cells. The functional organization of such units may be essential in deter mining malignant properties of RCC cells.