Cyclic Amp-Mediated Aquaporin-2 Translocation: Identification of Protein Kinase a Anchoring Proteins and the Role of the Small GTPases of the Rho Family

Abstract

The antidiuretic hormone arginine-vasopressin (AVP) regulates water reabsorption in inner medullary collecting duct (IMCD) principal cells by inducing the translocation of water channels (AQP2) from intracellular vesicles into the apical cell membranes (for review see: Klussmann et al., 2000). AVP initiates the activation of protein kinase A (PKA) by stimulation of the Gs/adenylyl cyclase system. Using a recently established primary culture model of rat IMCD cells (Maric et al., 1998) it was shown that the tethering of PKA by protein kinase A anchoring proteins (AKAPs; Scott et al., 2000) is a prerequisite for the translocation of AQP2 (Klussmann et al., 1999). In addition, in subcellular fractions from primary cultured rat IMCD cells enriched for AQP2-bearing vesicles or cell membranes various AKAPs various AKAPs were detected. Two strategies have been applied to identify AKAPs potentially involved in AQP2 translocation.