Arginine vasopressin (avp) stimulates phosphorylation of aquaporin
2 (aqp2) in rat renal tissue.
Nishimoto, Goro, Masato Yasui, Dailin Li, Marina Zelenina, S_ren
Nielsen, Anita Aperia and Angus C. Nairn.
1Department of Woman and Child Health, Karolinska Institute, St. G
divided by ran's Children's Hospital, 112 81 Stockholm, Sweden;
2Department of Cell Biology, Institute of Anatomy, University of
Aarhus, DK-8000 Aarhus, Denmark; and 3Laboratory of Molecular and
Cellular Neuroscience, The Rockefeller University, New York, NY
10021-6399
APStracts 5:0180F, 1998.
Aquaporin 2 (AQP2), the protein that mediates arginine vasopressin
(AVP)-regulated apical water transport in the renal collecting duct,
possesses a single consensus phosphorylation site for cAMP-dependent
protein kinase (PKA) at Ser 256. The aim of this study was to examine
whether AVP, and other agents that increase cAMP levels, could
stimulate the phosphorylation of AQP2 in intact rat renal tissue. Rat
renal papillae were pre-labeled with [32P], incubated with vehicle or
drugs, and then AQP2 was immunoprecipitated. Two polypeptides
corresponding to non-glycosylated (29 kDa) and glycosylated (35-48
kDa) AQP2 were identified by SDS-polyacrylamide gel electrophoresis.
AVP caused a time- and dose- dependent increase in phosphorylation of
both glycosylated and non-glycosylated AQP2. The threshold dose for a
significant increase in phosphorylation was 10 pM, which corresponds
to a physiological serum concentration of AVP. Maximal
phosphorylation was reached within 1 min of AVP incubation. This
effect on AQP2 phosphorylation was mimicked by the V2 agonist, dDAVP,
or forskolin. Two-dimensional phosphopeptide mapping indicated that
AVP and forskolin stimulated the phosphorylation of the same site in
AQP2. Immunoblot analysis using a phosphorylation state-specific
antiserum revealed an increase in phosphorylation of Ser 256 after
incubation of papillae with AVP. The results indicate that AVP
stimulates phosphorylation of AQP2 at Ser 256 via activation of PKA
and support the idea that this is one of the first steps leading to
increased water permeability in collecting duct cells.
Received 22 December 1997; accepted in final form 9 October 1998.
APS Manuscript Number F407-7.
Article publication pending Am. J. Physiol. (Renal Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 10 November 1998