A new member of the amphiphysin family connecting endocytosis and signal transduction pathways

Src homology 3 (SH3) domains are conserved modules which participate in protein interaction by recognizing proline-rich motifs on target molecules, To identify new SH3-containing proteins, we performed a two-hybrid screen with a proline-rich region of human SOS-1, One of the specific SOS-1 interacting clones that were isolated from a mouse brain cDNA 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 transcripts, Here, we report the amino acid sequence of a brain form of amphiphysin 2 (BRAMP2) encoded by a 2,5-kilobase mRNA, BRAMP2 associates in vitro with elements of the endocytosis machinery such as alpha-adaptin 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 after cell stimulation with nerve growth factor, suggesting that amphiphysin 2 may be connected to receptor-dependent signaling pathways, This hypothesis is strengthened by the ability of BRAMP2 to interact with the p21(ras) exchange factor SOS, in vitro, as a possible point of interconnection between the endocytic and signaling pathways.