Regulation of Aquaporin-2 Trafficking by Vasopressin in the Renal Collecting Duct

Line
Title: Regulation of Aquaporin-2 Trafficking by Vasopressin in the Renal Collecting Duct
Authors: Chou, Chung-Lin; Yip, Kay-Pong; Michea, Luis; Kador, Karl; Ferraris, Joan D.; Wade, James B.; Knepper, Mark
Publisher: Journal of Biological Chemistry
Date Published: November 24, 2000
Reference Number: 535
Line
In the renal collecting duct, vasopressin increases osmotic water permeability (Pf) by triggering trafficking of aquaporin-2 vesicles to the apical plasma membrane. We investigated the role of vasopressin-induced intracellular Ca2+ mobilization in this process. In isolated inner medullary collecting ducts (IMCDs), vasopressin (0.1 nM) and 8-(4-chlorophenylthio)-cAMP (0.1 mM) elicited marked increases in [Ca2+]i (fluo-4). Vasopressin-induced Ca2+ mobilization was completely blocked by preloading with the Ca2+ chelator BAPTA. In parallel experiments, BAPTA completely blocked the vasopressin-induced increase in Pf without affecting adenosine 3',5'-cyclic monophosphate (cAMP) production. Previously, we demonstrated the lack of activation of the phosphoinositide-signaling pathway by vasopressin in IMCD, suggesting an inositol 1,4,5-trisphosphate-independent mechanism of Ca2+ release. Evidence for expression of the type 1 ryanodine receptor (RyR1) in IMCD was obtained by immunofluorescence, immunoblotting, and reverse transcription-polymerase chain reaction. Ryanodine (100 ?M), a ryanodine receptor antagonist, blocked the arginine vasopressin-mediated increase in Pf and blocked vasopressin-stimulated redistribution of aquaporin-2 to the plasma membrane domain in primary cultures of IMCD cells, as assessed by immunofluorescence immunocytochemistry. Calmodulin inhibitors (W7 and trifluoperazine) blocked the Pf response to vasopressin and the vasopressin-stimulated redistribution of aquaporin-2. The results suggest that Ca2+ release from ryanodine-sensitive stores plays an essential role in vasopressin-mediated aquaporin-2 trafficking via a calmodulin-dependent mechanism.
The publisher has not granted permission to reproduce this article on our website.
You may, however, read this article at the Journal of Biological Chemistry website. To return to this page, use your "back" key.