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

2000; Elsevier BV; Volume: 275; Issue: 47 Linguagem: Inglês

10.1074/jbc.m005552200

1083-351X

Chung‐Lin Chou, Kay‐Pong Yip, Luis Michea, Karl E. Kador, Joan D. Ferraris, James B. Wade, Mark A. Knepper,

Pancreatic function and diabetes

In the renal collecting duct, vasopressin increases osmotic water permeability ( P f ) by triggering trafficking of aquaporin-2 vesicles to the apical plasma membrane. We investigated the role of vasopressin-induced intracellular Ca 2+ 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 [Ca 2+ ] i (fluo-4). Vasopressin-induced Ca 2+ mobilization was completely blocked by preloading with the Ca 2+ chelator BAPTA. In parallel experiments, BAPTA completely blocked the vasopressin-induced increase in P f 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 Ca 2+ 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 μm), a ryanodine receptor antagonist, blocked the arginine vasopressin-mediated increase in P f 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 P f response to vasopressin and the vasopressin-stimulated redistribution of aquaporin-2. The results suggest that Ca 2+ release from ryanodine-sensitive stores plays an essential role in vasopressin-mediated aquaporin-2 trafficking via a calmodulin-dependent mechanism.