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 Gα i3protein. Evidence is present...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2002-04, Vol.99 (7), p.4720-4724
Main Authors: Cho, Sang-Joon, A. K. M. Abdus Sattar, Jeong, Eun-Hwan, Satchi, Mylan, Cho, Jin Ah, Dash, Sudhansu, Mayes, Mary Sue, Stromer, Marvin H., Jena, Bhanu P.
Format: Article
Language:English
Subjects:
Acinar cells
Animals
Antibodies
Aquaporin 1
Aquaporins - physiology
Biological Sciences
Body Water - metabolism
Cell membranes
Cells
Cellular biology
Exocytosis
Guanosine Triphosphate - pharmacology
Membranes
Mercuric Chloride - pharmacology
Microscopy
P branes
Pancreas
Physiological regulation
Proteins
Rats
Secretion
Secretory vesicles
Secretory Vesicles - drug effects
Secretory Vesicles - metabolism
Swelling
Water channels
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Summary: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 Gα i3protein. 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.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.072083499