SGSM3 (also known as MAP, RUSC3, or RabGAP5) is expressed ubiquitously and functions as a regulator of small G protein RAP- and RAB-mediated neuronal signalling []. It is involved in modulating NGF-mediated neurite outgrowth and differentiation []. It also interacts with the tumour suppressor merlin and may play a role in the merlin-associated suppression of cell growth []. SGSM3 contains TBC, SH3, and RUN domains.This entry includes the SH3 domain of SGSM3.