RUSC1 is a 902 amino acid protein that contains a RUN domain and a SH3 domain. RUSC1’s RUN domain is necessary for NGF induced nuclear redistribution. RUSC1 is a putative signaling adapter which may play a role in neuronal differentiation. RUSC1 seems to be involved in signaling pathways that are regulated by the prolonged activation of MAPK. RUSC2 (RUN and SH3 domain containing 2), also known as Iporin, is a 1,516 amino acid cytoplasmic protein that is widely expressed, with highest levels in brain and testis. The RUN domain of RUSC2 is required for interaction with Rab 1A, Rab 1B and GM130. It is thought that RUSC2 may possibly function as a connector between endoplasmic reticulum (ER) derived vesicle targets triggered by the Rab 1 GTPases and a signaling pathway regulated by molecules containing SH3 and/or poly-proline regions. RUSC2 also consists of a SH3 domain, suggesting a role in protein-protein interactions.