title: Orchestrated content release from Drosophila glue-protein vesicles by a contractile actomyosin network.
abstract: Releasing content from large vesicles measuring several micrometres in diameter poses exceptional challenges to the secretory system. An actomyosin network commonly coats these vesicles, and is thought to provide the necessary force mediating efficient cargo release. Here we describe the spatial and temporal dynamics of the formation of this actomyosin coat around large vesicles and the resulting vesicle collapse, in live Drosophila melanogaster salivary glands. We identify the Formin family protein Diaphanous (Dia) as the main actin nucleator involved in generating this structure, and uncover Rho as an integrator of actin assembly and contractile machinery activation comprising this actomyosin network. High-resolution imaging reveals a unique cage-like organization of myosin II on the actin coat. This myosin arrangement requires branched-actin polymerization, and is critical for exerting a non-isotropic force, mediating efficient vesicle contraction.
authors.affiliation: Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Tal
authors.initials: T
authors.lastname: Rousso
authors.affiliation: Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Eyal D
authors.initials: ED
authors.lastname: Schejter
authors.affiliation: Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Ben-Zion
authors.initials: BZ
authors.lastname: Shilo
mesh_terms: D000199:Actins / Q000378:metabolism; D000205:Actomyosin / Q000378:metabolism*; D000818:Animals; D030801:Animals, Genetically Modified; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D005089:Exocytosis; D000080865:Formins; D005967:Glue Proteins, Drosophila / Q000378:metabolism*; D007700:Kinetics; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D018715:Microscopy, Video; D024462:Myosin Type II / Q000378:metabolism; D053141:Organelle Size; D012469:Salivary Glands / Q000378:metabolism* / Q000648:ultrastructure; D022142:Secretory Vesicles / Q000378:metabolism* / Q000648:ultrastructure; D059008:Time-Lapse Imaging; D054460:rho-Associated Kinases / Q000378:metabolism
chemical_list: D000199:Actins; D002352:Carrier Proteins; D029721:Drosophila Proteins; D000080865:Formins; D005967:Glue Proteins, Drosophila; D008565:Membrane Proteins; C081481:Rho protein, Drosophila; C106890:diaphanous protein, Drosophila; D000205:Actomyosin; D054460:rho-Associated Kinases; D024462:Myosin Type II