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(Hypertension. 2009;54:1070.)
© 2009 American Heart Association, Inc.

Original Articles

Caveolin-1 and Dopamine-Mediated Internalization of NaKATPase in Human Renal Proximal Tubule Cells

John J. Gildea; Jonathan A. Israel; Andrew K. Johnson; Jin Zhang; Pedro A. Jose; Robin A. Felder

From the Department of Pathology (J.J.G., J.A.I., A.K.J., R.A.F.), University of Virginia Health System, Charlottesville, Va; Children’s National Medical Center (P.A.J.), Center for Molecular Physiology, Department of Pediatrics, George Washington University, Washington, DC; Department of Pharmacology and Molecular Sciences, Johns Hopkins School of Medicine (J.Z.), Baltimore, Md.

Correspondence to Robin A. Felder, University of Virginia, PO Box 801400, Charlottesville, VA 22908. E-mail rfelder{at}virginia.edu

In moderate sodium-replete states, dopamine 1–like receptors (D₁R/D₅R) are responsible for regulating >50% of renal sodium excretion. This is partly mediated by internalization and inactivation of NaKATPase, when associated with adapter protein 2. We used dopaminergic stimulation via fenoldopam (D₁-like receptor agonist) to study the interaction among D₁-like receptors, caveolin-1 (CAV1), and the G protein–coupled receptor kinase type 4 in cultured human renal proximal tubule cells (RPTCs). We compared 2 groups of RPTCs, 1 of cell lines that were isolated from normal subjects (nRPTCs) and a second group of cell lines that have D₁-like receptors that are uncoupled (uncoupled RPTCs) from adenylyl cyclase second messengers. In nRPTCs, fenoldopam increased the plasma membrane expression of D₁R (10.0-fold) and CAV1 (1.3-fold) and markedly decreased G protein–coupled receptor kinase type 4 by 94±8%; no effects were seen in uncoupled RPTCs. Fenoldopam also increased the association of adapter protein 2 and NaKATPase by 53±9% in nRPTCs but not in uncoupled RPTCs. When CAV1 expression was reduced by 86.0±8.5% using small interfering RNA, restimulation of the D₁-like receptors with fenoldopam in nRPTCs resulted in only a 7±9% increase in association between adapter protein 2 and NaKATPase. Basal CAV1 expression and association with G protein–coupled receptor kinase type 4 was decreased in uncoupled RPTCs (58±5% decrease in association) relative to nRPTCs. We conclude that the scaffolding protein CAV1 is necessary for the association of D₁-like receptors with G protein–coupled receptor kinase type 4 and the adapter protein 2–associated reduction in plasma membrane NaKATPase.

Key Words: dopamine receptors • caveolin • proximal tubule • hypertension • GRK4 • NaKATPase • FRET