Snapin is a component of the biogenesis of lysosomal organelles complex-1 (BLOC-1), a complex required for the normal biogenesis of lysosome-related organelles, such as melanosomes and platelet dense granules [], and endosomal cargo sorting [].Snapin binds to SNAP-25, part of the SNARE complex that mediates the synaptic vesicle docking and fusion []. Snapin may modulate a step between vesicle priming, fusion and calcium-dependent neurotransmitter release through its ability to potentiate the interaction of synaptotagmin with the SNAREs and the plasma-membrane-associated protein SNAP25 []. Its phosphorylation state influences exocytotic protein interactions and may regulate synaptic vesicle exocytosis [, ]. It may also have a role in the mechanisms of SNARE-mediated membrane fusion in non-neuronal cells [].
Collectrin is a putative glycoprotein that shares homology with the C-terminal of angiotensin-converting enzyme-related carboxypeptidase (ACE2), but lacks the dipeptidyl carboxypeptidase catalytic domains. It is a target of HNF-1 in pancreatic beta cells and can increase exocytosis by interaction with snapin and facilitated SNARE complex formation [].
