title: Aquaporin 1 regulates GTP-induced rapid gating of water in secretory vesicles.
abstract: The swelling of secretory vesicles has been implicated in exocytosis, but the underlying mechanism of vesicle swelling remains largely unknown. Zymogen granules (ZGs), the membrane-bound secretory vesicles in exocrine pancreas, swell in response to GTP mediated by a G(alpha)i3 protein. Evidence is presented here that the water channel aquaporin-1 (AQP1) is present in the ZG membrane and participates in rapid GTP-induced vesicular water gating and swelling. Isolated ZGs exhibit low basal water permeability. However, exposure of granules to GTP results in a marked potentiation of water entry. Treatment of ZGs with the known water channel inhibitor Hg2+ is accompanied by a reversible loss in both the basal and GTP-stimulatable water entry and vesicle swelling. Introduction of AQP1-specific antibody raised against the carboxyl-terminal domain of AQP1 blocks GTP-stimulable swelling of vesicles. Our results demonstrate that AQP1 associated at the ZG membrane is involved in basal as well as GTP-induced rapid gating of water in ZGs of the exocrine pancreas.
authors.affiliation: Department of Physiology, Wayne State University School of Medicine, Detroit, MI 48201, USA.
authors.forename: Sang-Joon
authors.initials: SJ
authors.lastname: Cho
authors.forename: A K M Abdus
authors.initials: AK
authors.lastname: Sattar
authors.forename: Eun-Hwan
authors.initials: EH
authors.lastname: Jeong
authors.forename: Mylan
authors.initials: M
authors.lastname: Satchi
authors.forename: Jin Ah
authors.initials: JA
authors.lastname: Cho
authors.forename: Sudhansu
authors.initials: S
authors.lastname: Dash
authors.forename: Mary Sue
authors.initials: MS
authors.lastname: Mayes
authors.forename: Marvin H
authors.initials: MH
authors.lastname: Stromer
authors.forename: Bhanu P
authors.initials: BP
authors.lastname: Jena
mesh_terms: D000818:Animals; D051398:Aquaporin 1; D020346:Aquaporins / Q000502:physiology*; D001834:Body Water / Q000378:metabolism*; D005089:Exocytosis; D006160:Guanosine Triphosphate / Q000494:pharmacology*; D008627:Mercuric Chloride / Q000494:pharmacology; D051381:Rats; D022142:Secretory Vesicles / Q000187:drug effects / Q000378:metabolism*
chemical_list: C496022:Aqp1 protein, rat; D020346:Aquaporins; D051398:Aquaporin 1; D008627:Mercuric Chloride; D006160:Guanosine Triphosphate