Spring, a novel RING finger protein that regulates synaptic vesicle exocytosis.

The synaptosome-associated protein of 25 kDa (SNAP-25) interacts with syntaxin 1 and vesicle-associated membrane protein 2 (VAMP2) to form a ternary soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptor (SNARE) complex that is essential for synaptic vesicle exocytosis. We report a novel RING finger protein, Spring, that specifically interacts with SNAP-25. Spring is exclusively expressed in brain and is concentrated at synapses. The association of Spring with SNAP-25 abolishes the ability of SNAP-25 to interact with syntaxin 1 and VAMP2 and prevents the assembly of the SNARE complex. Overexpression of Spring or its SNAP-25-interacting domain reduces Ca(2+)-dependent exocytosis from PC12 cells. These results indicate that Spring may act as a regulator of synaptic vesicle exocytosis by controlling the availability of SNAP-25 for the SNARE complex formation.