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The Journal of Neuroscience, July 26, 2006, 26(30):7826-7838; doi:10.1523/JNEUROSCI.1866-06.2006
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Cellular/Molecular
Expression and Function of SNAP-25 as a Universal SNARE Component in GABAergic Neurons
Lawrence C. R. Tafoya, Manuel Mameli, Teiko Miyashita, John F. Guzowski, C. Fernando Valenzuela, andMichael C. Wilson Department of Neurosciences, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131
Correspondence should be addressed to Michael C. Wilson, Department of Neurosciences, University of New Mexico Health Sciences Center, Albuquerque, NM 87131. mwilson{at}salud.unm.edu
Intracellular vesicular trafficking and membrane fusion are important processes for nervous system development and for the function of neural circuits. Synaptosomal-associated protein 25 kDa (SNAP-25) is a component of neural soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) core complexes that mediate the exocytotic release of neurotransmitters at chemical synapses. Previous results from mouse mutant models and pharmacological/neurotoxin blockades have demonstrated a critical role for SNAP-25-containing SNARE complexes in action potential (AP)-dependent release at cholinergic and glutamatergic synapses and for calcium-triggered catecholamine release from chromaffin cells. To examine whether SNAP-25 participates in the evoked release of other neurotransmitters, we investigated the expression and function of SNAP-25 in GABAergic terminals. Patch-clamp recordings in fetal Snap25-null mutant cortex demonstrated that ablation of SNAP-25 eliminated evoked GABAA receptor-mediated postsynaptic responses while leaving a low level of spontaneous AP-independent events intact, supporting the involvement of SNAP-25 in the regulated synaptic transmission of early developing GABAergic neurons. In hippocampal cell cultures of wild-type mice, punctate staining of SNAP-25 colocalized with both GABAergic and glutamatergic synaptic markers, whereas stimulus-evoked vesicular recycling was abolished at terminals of both transmitter phenotypes in Snap25–/– neurons. Moreover, immunohistochemistry and fluorescence in situ hybridization revealed coexpression of SNAP-25, VGAT (vesicular GABA transporter), and GAD65/67 (glutamic acid decarboxylase 65/67) in interneurons within several regions of the adult brain. Our results thus provide evidence that SNAP-25 is critical for evoked GABA release during development and is expressed in the presynaptic terminals of mature GABAergic neurons, consistent with its function as a component of a fundamental core SNARE complex required for stimulus-driven neurotransmission.
Key words: SNARE proteins; GABAergic neuron; inhibitory neurotransmission; SNAP-25; neuroexocytosis; CNS development; GABA transporter
Received Dec. 30, 2005; revised June 16, 2006; accepted June 19, 2006.
Correspondence should be addressed to Michael C. Wilson, Department of Neurosciences, University of New Mexico Health Sciences Center, Albuquerque, NM 87131. mwilson{at}salud.unm.edu
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