title: Syntaxin clusters assemble reversibly at sites of secretory granules in live cells.
abstract: Syntaxin resides in the plasma membrane, where it helps to catalyze membrane fusion during exocytosis. The protein also forms clusters in cell-free and granule-free plasma-membrane sheets. We imaged the interaction between syntaxin and single secretory granules by two-color total internal reflection microscopy in PC12 cells. Syntaxin-GFP assembled in clusters at sites where single granules had docked at the plasma membrane. Clusters were intermittently present at granule sites, as syntaxin molecules assembled and disassembled in a coordinated fashion. Recruitment to granules required the N-terminal domain of syntaxin, but not the entry of syntaxin into SNARE complexes. Clusters facilitated exocytosis and disassembled once exocytosis was complete. Syntaxin cluster formation defines an intermediate step in exocytosis.
authors.affiliation: Department of Medical Cell Biology, Uppsala University, Uppsala 75123, Sweden.
authors.forename: S
authors.initials: S
authors.lastname: Barg
authors.forename: M K
authors.initials: MK
authors.lastname: Knowles
authors.forename: X
authors.initials: X
authors.lastname: Chen
authors.forename: M
authors.initials: M
authors.lastname: Midorikawa
authors.forename: Wolfhard
authors.initials: W
authors.lastname: Almers
mesh_terms: D000818:Animals; D002470:Cell Survival; D005089:Exocytosis; D005453:Fluorescence; D049452:Green Fluorescent Proteins / Q000378:metabolism; D050505:Mutant Proteins / Q000378:metabolism; D016716:PC12 Cells; D050765:Qa-SNARE Proteins / Q000378:metabolism*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D022142:Secretory Vesicles / Q000378:metabolism*; D010959:Tissue Plasminogen Activator / Q000378:metabolism; D050988:Vesicle-Associated Membrane Protein 2 / Q000378:metabolism
chemical_list: D050505:Mutant Proteins; D050765:Qa-SNARE Proteins; D011993:Recombinant Fusion Proteins; D050988:Vesicle-Associated Membrane Protein 2; D049452:Green Fluorescent Proteins; D010959:Tissue Plasminogen Activator