Rab 3, a neural/neuroendocrine-specific member of the Rab family, is involved in Ca2+-regulated exocytosis and functions in an inhibitory capacity, controlling the recruitment and pooling of secretory vesicles at the plasma membrane. The Rim (Rab 3 interacting molecule) family of proteins (Rim1, Rim2, Rim3 and Rim4) are multidomain adaptors that regulate Rab 3 activity and sub-sequent neurotransmitter release. Rim3, also known as RIMS3 (regulating synaptic membrane exocytosis 3) or NIM3, is a 308 amino acid member of the Rim family. Localized to the synapse and to cell junctions, Rim3 contains one C2 domain and is thought to play an important role in the regulation of synaptic membrane exocytosis. Rim3, a protein that may be phosphorylated upon DNA damage, is expressed throughout the body with highest levels present in brain tissue.