title: Roles of Munc18-3 in amylase release from rat parotid acinar cells.
abstract: Several "soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptor" (SNARE) proteins have been identified in rat parotid acinar cells, including VAMP-2, syntaxin 4, and SNAP-23. Furthermore, an association between Munc18c (Munc18-3) and syntaxin 4 has been reported. However, the role of Munc18-3 in secretory granule exocytosis on parotid acinar cells remains unclear. In the present study, we investigated the role of Munc18-3 in rat parotid acinar cells. Munc18-3 was localized on the apical plasma membrane where exocytosis occurs and interacted with syntaxin 4. Anti-Munc18-3 antibody dose-dependently decreased isoproterenol (IPR)-induced amylase release from SLO-permeabilized parotid acinar cells. Furthermore, stimulation of the acinar cells with IPR induced translocation of Munc18-3 from the plasma membrane to the cytosol. Munc-18-3 was not phosphorylated by a catalytic subunit of protein kinase (PK) A but phosphorylated by PKC. Treatment of the plasma membrane with PKC but not PKA induced displacement of Munc18-3 from the membrane. The results indicate that Munc18-3 regulates exocytosis in the acinar cells for IPR-induced amylase release and that phosphorylation of Munc18-3 by PKA is not involved in the mechanism.
authors.affiliation: Department of Biochemistry, School of Dentistry at Niigata, The Nippon Dental University, 1-8 Hamaura-cho, Niigata 951-8580, Japan. imaiak@ngt.ndu.ac.jp
authors.forename: Akane
authors.initials: A
authors.lastname: Imai
authors.forename: Tomoko
authors.initials: T
authors.lastname: Nashida
authors.forename: Hiromi
authors.initials: H
authors.lastname: Shimomura
mesh_terms: D000681:Amylases / Q000096:biosynthesis / Q000378:metabolism*; D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D001426:Bacterial Proteins; D001483:Base Sequence; D002462:Cell Membrane / Q000378:metabolism; D002463:Cell Membrane Permeability / Q000187:drug effects / Q000502:physiology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D007545:Isoproterenol / Q000494:pharmacology; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D051938:Munc18 Proteins; D009419:Nerve Tissue Proteins; D010306:Parotid Gland / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D011506:Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D050765:Qa-SNARE Proteins; D051381:Rats; D022142:Secretory Vesicles / Q000378:metabolism; D013301:Streptolysins / Q000494:pharmacology; D013347:Subcellular Fractions / Q000378:metabolism; D033921:Vesicular Transport Proteins
chemical_list: D000906:Antibodies; D001426:Bacterial Proteins; D008565:Membrane Proteins; D051938:Munc18 Proteins; D009419:Nerve Tissue Proteins; D011506:Proteins; D050765:Qa-SNARE Proteins; D013301:Streptolysins; C497944:Stxbp3 protein, rat; D033921:Vesicular Transport Proteins; C025964:streptolysin O; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D000681:Amylases; D007545:Isoproterenol