Gα12- and Gα13-protein subunit linkage of D5 dopamine receptors in the nephron

Abstract

The roles of the G-protein a-subunits, Gs, Gi, and Gq/11, in the signal transduction of the D1-like dopamine receptors, D1 and D5, have been deciphered. Gα12 and Gα13, members of the 4th family of G protein subunits, are not linked with D1 receptors, and their linkage to D5 receptors is not known. Therefore, we studied the expression of Gα12 and Gα13 and interaction with D5 dopamine receptors in the kidney from normotensive Wistar-Kyoto (WKY) rats and D5 receptor-transfected HEK293 cells. Gα12 and Gα13 were found in the proximal tubule, distal convoluted tubule, and artery and vein in the WKY rat kidney. Whereas Gα12 was expressed in the ascending limb of Henle, Gα13 was expressed in the collecting duct and juxtaglomerular cells. In renal proximal tubules, Gα12 and Gα13, as with D5 receptors, were expressed in brush border membranes. Laser confocal microscopy revealed the colocalization of D5 receptors with Gα12 and Gα13 in rat renal brush border membranes, immortalized rat renal proximal tubule cells, and D5 receptor-transfected HEK293 cells. In these cells, a D1-like agonist, fenoldopam, increased the association of Gα12 and Gα13 with D5 receptors, results that were corroborated by immunoprecipitation experiments. We conclude that although both D1 and D5 receptors are linked to Gαs, they are differentially linked to Gα12 and Gα13. The consequences of the differential G-protein subunit linkage on D1- and D5-mediated sodium transport remains to be determined.