Phosphorylation of protein phosphatase-1 inhibitors, inhibitor-1 and DARPP-32, in renal medulla.
Inhibitor-1 and DARPP-32 (dopamine and cAMP-regulated phosphoprotein, Mr 32 kDa) are each phosphorylated by cAMP-dependent protein kinase, resulting in their conversion to potent inhibitors of protein phosphatase-1. Protein phosphatase-1 is involved in the regulation of Na(+) reabsorption from renal tubule by modulating the activity of Na(+),K(+)-ATPase. In this study, we have investigated the regulation of inhibitor-1 and DARPP-32 phosphorylation in slices of renal medulla. Activation of cAMP-dependent protein kinase by forskolin and 8-bromo-cAMP increased the level of phosphorylated inhibitor-1. Okadaic acid (1 microM), used to inhibit protein phosphatase-2A, increased the level of phosphorylated inhibitor-1, but cyclosporin A had no effect. DARPP-32, like inhibitor-1, was phosphorylated by cAMP-dependent protein kinase and dephosphorylated only by protein phosphatase-2A. These data demonstrate that the phosphorylation of inhibitor-1 and DARPP-32 is regulated by the balance of phosphorylation by cAMP-dependent protein kinase and dephosphorylation by protein phosphatase-2A in renal medulla. Furthermore, the phosphorylation step is regulated by pharmacological stimuli such as activation of beta(1)-adrenoceptors and dopamine D1 receptors.
Higuchi
E
E
Department of Pediatrics and Child Health, Kurume University School of Medicine, Fukuoka 830-0011, Kurume, Japan.
Nishi
A
A
Higashi
H
H
Ito
Y
Y
Kato
H
H
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D001552:Benzazepines / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D002352:Carrier Proteins; D005576:Colforsin / Q000494:pharmacology; D018491:Dopamine Agonists / Q000494:pharmacology; D051937:Dopamine and cAMP-Regulated Phosphoprotein 32; D004791:Enzyme Inhibitors / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D007476:Ionophores / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D007679:Kidney Medulla / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009419:Nerve Tissue Proteins; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors*; D010750:Phosphoproteins / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D054645:Protein Phosphatase 1; D054648:Protein Phosphatase 2; D016601:RNA-Binding Proteins / Q000187:drug effects / Q000378:metabolism*
D000318:Adrenergic beta-Agonists; D001552:Benzazepines; D002352:Carrier Proteins; D018491:Dopamine Agonists; D051937:Dopamine and cAMP-Regulated Phosphoprotein 32; D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D007476:Ionophores; D009419:Nerve Tissue Proteins; D010750:Phosphoproteins; D016601:RNA-Binding Proteins; C021042:protein phosphatase inhibitor-1; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D000001:Calcimycin; C067113:SK&F 81297; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D054648:Protein Phosphatase 2; D007545:Isoproterenol