title: Munc18-1 domain-1 controls vesicle docking and secretion by interacting with syntaxin-1 and chaperoning it to the plasma membrane.
abstract: Munc18-1 plays pleiotropic roles in neurosecretion by acting as 1) a molecular chaperone of syntaxin-1, 2) a mediator of dense-core vesicle docking, and 3) a priming factor for soluble N-ethylmaleimide-sensitive factor attachment protein receptor-mediated membrane fusion. However, how these functions are executed and whether they are correlated remains unclear. Here we analyzed the role of the domain-1 cleft of Munc18-1 by measuring the abilities of various mutants (D34N, D34N/M38V, K46E, E59K, K46E/E59K, K63E, and E66A) to bind and chaperone syntaxin-1 and to restore the docking and secretion of dense-core vesicles in Munc18-1/-2 double-knockdown cells. We identified striking correlations between the abilities of these mutants to bind and chaperone syntaxin-1 with their ability to restore vesicle docking and secretion. These results suggest that the domain-1 cleft of Munc18-1 is essential for binding to syntaxin-1 and thereby critical for its chaperoning, docking, and secretory functions. Our results demonstrate that the effect of the alleged priming mutants (E59K, D34N/M38V) on exocytosis can largely be explained by their reduced syntaxin-1-chaperoning functions. Finally, our data suggest that the intracellular expression and distribution of syntaxin-1 determines the level of dense-core vesicle docking.
authors: Division of Fundamental Neurobiology, University Health Network, Toronto ON M5T 2S8, Canada.
authors: Gayoung A
authors: GA
authors: Han
authors: Nancy T
authors: NT
authors: Malintan
authors: Ner Mu Nar
authors: NM
authors: Saw
authors: Lijun
authors: L
authors: Li
authors: Liping
authors: L
authors: Han
authors: Frederic A
authors: FA
authors: Meunier
authors: Brett M
authors: BM
authors: Collins
authors: Shuzo
authors: S
authors: Sugita
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D002151:Calorimetry; D002462:Cell Membrane / Q000378:metabolism*; D015870:Gene Expression; D006801:Humans; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism; D051938:Munc18 Proteins / Q000235:genetics / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism; D016716:PC12 Cells; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D021381:Protein Transport; D051381:Rats; D022142:Secretory Vesicles / Q000378:metabolism* / Q000648:ultrastructure; D050827:Syntaxin 1 / Q000235:genetics / Q000378:metabolism*; D013816:Thermodynamics; D017186:Titrimetry
chemical_list: D018832:Molecular Chaperones; D051938:Munc18 Proteins; C494213:Stx1a protein, rat; C497939:Stxbp1 protein, rat; D050827:Syntaxin 1; D009638:Norepinephrine