Aquaporin 1 regulates GTP-induced rapid gating of water in secretory vesicles.
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.
Cho
Sang-Joon
SJ
Department of Physiology, Wayne State University School of Medicine, Detroit, MI 48201, USA.
Sattar
A K M Abdus
AK
Jeong
Eun-Hwan
EH
Satchi
Mylan
M
Cho
Jin Ah
JA
Dash
Sudhansu
S
Mayes
Mary Sue
MS
Stromer
Marvin H
MH
Jena
Bhanu P
BP
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*
C496022:Aqp1 protein, rat; D020346:Aquaporins; D051398:Aquaporin 1; D008627:Mercuric Chloride; D006160:Guanosine Triphosphate