DIFFERENTIAL EXPRESSION OF SNAP-25 PROTEIN ISOFORMS DURING DIVERGENT VESICLE FUSION EVENTS OF NEURAL DEVELOPMENT

The presynaptic plasma membrane protein SNAP-25 (synaptosome-associate d protein of 25 kDa) has been implicated as one of several neural-spec ific components that direct constitutive fusion mechanisms to the regu lated vesicle trafficking and exocytosis of neurotransmitter release. There exist two alternatively spliced isoforms of SNAP-25, a and b, wh ich differ in a putative membrane-interacting domain. We show that the se two isoforms have distinct quantitative and anatomical patterns of expression during brain development, in neurons, and in neuroendocrine cells and that the proteins localize differently in neurites of trans fected PC12 pheochromocytoma cells. These findings indicate that alter native isoforms of SNAP-25 may play distinct roles in vesicular fusion events required for membrane addition during axonal outgrowth and for release of neuromodulatory peptides and neurotransmitters.