Interacts with RIMS1, RIMS2 and TSPO. Preferentially expressed in the mitochondria in the presence of TSPO. Predominantly expressed in the brain. The SH3 and proline-rich domain is required for the interaction with TSPO and the second SH3 domain mediates binding to a proline-rich motif in RIMS1 and RIMS2. Due to intron retention. Belongs to the RIMBP family.