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  • Title: S-nitrosylation of syntaxin 1 at Cys(145) is a regulatory switch controlling Munc18-1 binding.
    Author: Palmer ZJ, Duncan RR, Johnson JR, Lian LY, Mello LV, Booth D, Barclay JW, Graham ME, Burgoyne RD, Prior IA, Morgan A.
    Journal: Biochem J; 2008 Aug 01; 413(3):479-91. PubMed ID: 18452404.
    Abstract:
    Exocytosis is regulated by NO in many cell types, including neurons. In the present study we show that syntaxin 1a is a substrate for S-nitrosylation and that NO disrupts the binding of Munc18-1 to the closed conformation of syntaxin 1a in vitro. In contrast, NO does not inhibit SNARE {SNAP [soluble NSF (N-ethylmaleimide-sensitive fusion protein) attachment protein] receptor} complex formation or binding of Munc18-1 to the SNARE complex. Cys(145) of syntaxin 1a is the target of NO, as a non-nitrosylatable C145S mutant is resistant to NO and novel nitrosomimetic Cys(145) mutants mimic the effect of NO on Munc18-1 binding in vitro. Furthermore, expression of nitrosomimetic syntaxin 1a in living cells affects Munc18-1 localization and alters exocytosis release kinetics and quantal size. Molecular dynamic simulations suggest that NO regulates the syntaxin-Munc18 interaction by local rearrangement of the syntaxin linker and H3c regions. Thus S-nitrosylation of Cys(145) may be a molecular switch to disrupt Munc18-1 binding to the closed conformation of syntaxin 1a, thereby facilitating its engagement with the membrane fusion machinery.
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