title: Munc18/Syntaxin interaction kinetics control secretory vesicle dynamics.
abstract: In neuronal and hormonal release, regulated exocytosis requires an essential set of proteins: the soluble N-ethylmaleimide sensitive-factor attachment receptor proteins (SNAREs) syntaxin 1, SNAP-25, VAMP, and their regulator, Munc18. Recently, it was found that Munc18-1 can interact with syntaxin 1 through distinct mechanisms: an inhibitory mode enveloping syntaxin (mode 1), sequestering it from SNARE protein interactions, and direct binding to an evolutionarily conserved N-terminal peptide of syntaxin (mode 2/3). The latter interaction has been proposed to control "priming" of the fusion reaction, defined using electrophysiology, but it is unknown how this interaction is regulated, and any dynamic effect at the molecular or vesicular level in cells remains undiscovered. We now show that a phosphorylation site in syntaxin 1 (Ser(14)) regulates the N-terminal interaction with Munc18-1. Probing syntaxin 1 association with Munc18-1, in real-time and in living cells, we found that modification of Ser(14) modulated the dynamics of this interaction, specifically at the plasma membrane. Destabilization of this dynamic interaction enhanced vesicle immobilization at the plasma membrane with a resulting inhibition of exocytosis.
authors.affiliation: From the Centre for Integrative Physiology, University of Edinburgh, George Square, Edinburgh EH8 9XD, Scotland, United Kingdom.
authors.forename: Colin
authors.initials: C
authors.lastname: Rickman
authors.affiliation: From the Centre for Integrative Physiology, University of Edinburgh, George Square, Edinburgh EH8 9XD, Scotland, United Kingdom. Electronic address: rory.duncan@ed.ac.uk.
authors.forename: Rory R
authors.initials: RR
authors.lastname: Duncan
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D047390:Casein Kinase II / Q000378:metabolism; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D005089:Exocytosis; D007700:Kinetics; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D051938:Munc18 Proteins / Q000235:genetics / Q000378:metabolism*; D016716:PC12 Cells; D010766:Phosphorylation; D011485:Protein Binding; D051381:Rats; D022142:Secretory Vesicles / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000235:genetics / Q000378:metabolism; D050827:Syntaxin 1 / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
chemical_list: D008164:Luminescent Proteins; D051938:Munc18 Proteins; D050827:Syntaxin 1; D012694:Serine; D047390:Casein Kinase II