| First Author | Bronk P | Year | 2007 |
| Journal | J Neurophysiol | Volume | 98 |
| Issue | 2 | Pages | 794-806 |
| PubMed ID | 17553942 | Mgi Jnum | J:147690 |
| Mgi Id | MGI:3841908 | Doi | 10.1152/jn.00226.2007 |
| Citation | Bronk P, et al. (2007) Differential effects of SNAP-25 deletion on Ca2+ -dependent and Ca2+ -independent neurotransmission. J Neurophysiol 98(2):794-806 |
| abstractText | At the synapse, SNAP-25, along with syntaxin/HPC-1 and synaptobrevin/VAMP, forms SNARE N-ethylmaleimide-sensitive factor [soluble (NSF) attachment protein receptor] complexes that are thought to catalyze membrane fusion. Results from neuronal cultures of synaptobrevin-2 knockout (KO) mice showed that loss of synaptobrevin has a more severe effect on calcium-evoked release than on spontaneous release or on release evoked by hypertonicity. In this study, we recorded neurotransmitter release from neuronal cultures of SNAP-25 KO mice to determine whether they share this property. In neurons lacking SNAP-25, as those deficient in synaptobrevin-2, we found that approximately 10-12% of calcium-independent excitatory and inhibitory neurotransmitter release persisted. However, in contrast to synaptobrevin-2 knockouts, this remaining readily releasable pool in SNAP-25-deficient synapses was virtually insensitive to calcium-dependent-evoked stimulation. Although field stimulation reliably evoked neurotransmitter release in synaptobrevin-2 KO neurons, responses were rare in neurons lacking SNAP-25, and unlike synaptobrevin-2-deficient synapses, SNAP-25-deficient synapses did not exhibit facilitation of release during high-frequency stimulation. This severe loss of evoked exocytosis was matched by a reduction, but not a complete loss, of endocytosis during evoked stimulation. Moreover, synaptic vesicle turnover probed by FM-dye uptake and release during hypertonic stimulation was relatively unaffected by the absence of SNAP-25. This last difference indicates that in contrast to synaptobrevin, SNAP-25 does not directly function in endocytosis. Together, these results suggest that SNAP-25 has a more significant role in calcium-secretion coupling than synaptobrevin-2. |
