A NEW MEMBER OF THE AMPHIPHYSIN FAMILY CONNECTING ENDOCYTOSIS AND SIGNAL-TRANSDUCTION PATHWAYS

Src homology 3 (SH3) domains are conserved modules which participate i n protein interaction by recognizing proline-rich motifs on target mol ecules, To identify new SH3-containing proteins, we performed a two-hy brid screen with a proline-rich region of human SOS-1, One of the spec ific SOS-1 interacting clones that were isolated from a mouse brain cD NA library defines a new protein that was named amphiphysin 2 because of its homology to the previously reported amphiphysin. Amphiphysin 2 is expressed in a number of mouse tissues through multiple RNA transcr ipts, Here, we report the amino acid sequence of a brain form of amphi physin 2 (BRAMP2) encoded by a 2,5-kilobase mRNA, BRAMP2 associates in vitro with elements of the endocytosis machinery such as alpha-adapti n and dynamin, On a biosensor surface, the BRAMP2/dynamin interaction appeared to be direct and partly dependent on a proline-rich sequence of dynamin, Association with dynamin was also observed in PC12 cells a fter cell stimulation with nerve growth factor, suggesting that amphip hysin 2 may be connected to receptor-dependent signaling pathways, Thi s hypothesis is strengthened by the ability of BRAMP2 to interact with the p21(ras) exchange factor SOS, in vitro, as a possible point of in terconnection between the endocytic and signaling pathways.