RA70 is a src kinase-associated protein expressed ubiquitously

RA70, which is expressed during neuronal differentiation of P19 EC, is high ly homologous to human src kinase-associated phosphoprotein (SKAP55). Here we isolated human full-length RA70 cDNA. Unlike SKAP55, which is specifical ly expressed in thymus and T cells, RA70 was expressed ubiquitously in vari ous tissues including lung, skeletal muscle, and spleen, and in various cel l lines including human monocytic leukemia (U937) cells, but RA70 was undet ectable in thymus and T cell lymphoma (Jurkat) cells. RA70 as well as SKAP5 5 proved to be a protein with molecular weight 55 kDa associated with SH2 d omain of Fyn. Interaction between RA70 and src family kinases, Fyn, Hck and Lyn, was detected during monocytes/ macrophage-differentiation of U937 cel ls. Thus, like SKAP55, RA70 is an adaptor protein of the src family kinases . RA70 may play an essential role in the src signaling pathway in various c ells. (C) 1998 Academic Press.