Syntaxin 1A regulates dopamine transporter activity, phosphorylation and surface expression.

We investigated the functional relationship between the soluble N-ethylmaleimide-sensitive factor attachment receptor (SNARE) protein syntaxin 1A (syn 1A) and the dopamine transporter (DAT) by treating rat striatal tissue with Botulinum Neurotoxin C (BoNT/C) and co-transfecting syn 1A with DAT in non-neuronal cells, followed by analysis of DAT activity, phosphorylation, and regulation. Treatment of striatal slices with BoNT/C resulted in elevated dopamine (DA) transport Vmax and reduced DAT phosphorylation, while heterologous co-expression of syn 1A led to reduction in DAT surface expression and transport Vmax. Syn 1A was present in DAT immunoprecipitation complexes, supporting a direct or indirect interaction between the proteins. Phorbol ester regulation of DA transport activity was retained in BoNT/C-treated synaptosomes and syn 1A transfected cells, demonstrating that protein kinase C (PKC) and syn 1A effects occur through independent processes. These findings reveal a novel mechanism for regulation of DAT activity and phosphorylation, and suggest the potential for syn 1A to impact DA neurotransmission through effects on reuptake. Copyright 2010 IBRO. Published by Elsevier Ltd. All rights reserved.