SH3MD2 acts as a scaffold protein, contributes to Rac-induced signal transduction such as JNKs (MAPK8 and MAPK9) activation and induces apoptosis. Within a signaling complex, it probably recruits protein kinases such as MAP3K10 or MAP3K11 which are in turn activated leading to the sequential activation of MAP2K4, MAP2K7 and JNKs (MAPK8 and MAPK9). SH3MD2 may be involved in targeting of HIV-1 GAG and GAG-POL polyproteins to the plasma membrane. This gene encodes a protein containing an N-terminus RING-finger, four SH3 domains, and a region implicated in binding of the Rho GTPase Rac. Via the RING-finger, the encoded protein has been shown to function as an ubiquitin-protein ligase involved in protein sorting at the trans-Golgi network. The encoded protein may also act as a scaffold for the c-Jun N-terminal kinase signaling pathway, facilitating the formation of a functional signaling module. There are two named isoforms.