title: MADD/DENN/Rab3GEP functions as a guanine nucleotide exchange factor for Rab27 during granule exocytosis of rat parotid acinar cells.
abstract: We previously reported that the small GTPase Rab27 and its effectors regulate isoproterenol (IPR)-stimulated amylase release from rat parotid acinar cells. Although activation of Rab27 by a specific guanine nucleotide exchange factor (GEF) is thought to be required for amylase release, its activation mechanism is poorly understood, because GEF for Rab27 has not been reported in parotid acinar cells. In the present study, we investigated the possible involvement of MADD/DENN/Rab3GEP, which was recently described as a Rab27-GEF in melanocytes, in amylase release from rat parotid acinar cells. Reverse transcription-PCR analyses indicated that mRNA of DENND family members, including MADD, was expressed in parotid acinar cells. MADD protein was also expressed in the cytosolic fraction of parotid acinar cells. Incubation of an antibody against the C-terminal 150 amino acids of MADD (anti-MADD-C antibody) with streptolysin O-permeabilized parotid acinar cells caused not only inhibition of IPR-induced amylase release but also reduction in the amount of GTP-Rab27. Our findings indicated that MADD functions as a GEF for Rab27 in parotid acinar cells and that its GEF activity for Rab27, i.e., GDP/GTP cycling, is required for IPR-induced amylase release.
authors.affiliation: Department of Biochemistry, The Nippon Dental University, School of Life Dentistry at Niigata, 1-8 Hamaura-cho, Chuo-ku, Niigata 951 8580, Japan. imaiak@ngt.ndu.ac.jp
authors.forename: Akane
authors.initials: A
authors.lastname: Imai
authors.forename: Morié
authors.initials: M
authors.lastname: Ishida
authors.forename: Mitsunori
authors.initials: M
authors.lastname: Fukuda
authors.forename: Tomoko
authors.initials: T
authors.lastname: Nashida
authors.forename: Hiromi
authors.initials: H
authors.lastname: Shimomura
mesh_terms: D061354:Acinar Cells / Q000166:cytology* / Q000378:metabolism; D000681:Amylases / Q000378:metabolism*; D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002463:Cell Membrane Permeability / Q000187:drug effects; D053418:Death Domain Receptor Signaling Adaptor Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D005089:Exocytosis; D015870:Gene Expression; D020662:Guanine Nucleotide Exchange Factors / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D008297:Male; D010306:Parotid Gland / Q000166:cytology*; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D013301:Streptolysins / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000378:metabolism*; D000075745:rab27 GTP-Binding Proteins
chemical_list: D001426:Bacterial Proteins; D053418:Death Domain Receptor Signaling Adaptor Proteins; D020662:Guanine Nucleotide Exchange Factors; C491370:Madd protein, rat; D012333:RNA, Messenger; D013301:Streptolysins; D000075745:rab27 GTP-Binding Proteins; C025964:streptolysin O; D006160:Guanosine Triphosphate; D000681:Amylases; C512961:Rab27a protein, rat; D020691:rab GTP-Binding Proteins
keywords: Amylase release; DENND family; Guanine nucleotide exchange factor; MADD; Parotid acinar cells; Rab27