Role of cAMP-PKA-PLC signaling cascade on dopamine-induced PKC-mediated inhibition of renal Na(+)-K(+)-ATPase activity.

We studied the molecular events set into motion by stimulation of D(1)-like receptors downstream of Na(+)-K(+)-ATPase, while measuring apical-to-basal ouabain-sensitive, amphotericin B-induced increases in short-circuit current in opossum kidney (OK) cells. The D(1)-like receptor agonist SKF-38393 decreased Na(+)-K(+)-ATPase activity (IC(50), 130 nM). This effect was prevented by the D(1)-like receptor antagonist SKF-83566, overnight cholera toxin treatment, the protein kinase A (PKA) antagonist H-89, or the PKC antagonist chelerythrine, but not the mitogen-activated PK inhibitor PD-098059 or phosphatidylinositol 3-kinase inhibitors wortmannin and LY-294002. Dibutyryl cAMP (DBcAMP) and phorbol 12,13-dibutyrate (PDBu) both effectively reduced Na(+)-K(+)-ATPase activity. PKA downregulation abolished the inhibitory effects of SKF-38393 and DBcAMP but not those of PDBu. PKC downregulation abolished inhibition by PDBu, SKF-38393, and DBcAMP. The phospholipase C (PLC) inhibitor U-73122 prevented inhibition by SKF-38393 and DBcAMP. However, DBcAMP increased PLC activity. Although OK cells express both G(s)alpha and G(q/11)alpha proteins, D(1)-like receptors are coupled to G(s)alpha proteins only, as evidenced by studies in cells treated overnight with specific antibodies raised against G(s)alpha and G(q/11)alpha proteins. We conclude that PLC and Na(+)-K(+)-ATPase are effector proteins for PKA and PKC, respectively, after stimulation of D(1)-like receptors coupled to G(s)alpha proteins, in a sequence of events that begins with adenylyl cyclase-PKA system activation followed by PLC-PKC system activation.