title: Caveolin-1 and dopamine-mediated internalization of NaKATPase in human renal proximal tubule cells.
abstract: 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.
authors.affiliation: Department of Pathology, University of Virginia Health System, Charlottesville, VA 22908, USA.
authors.forename: John J
authors.initials: JJ
authors.lastname: Gildea
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Israel
authors.forename: Andrew K
authors.initials: AK
authors.lastname: Johnson
authors.forename: Jin
authors.initials: J
authors.lastname: Zhang
authors.forename: Pedro A
authors.initials: PA
authors.lastname: Jose
authors.forename: Robin A
authors.initials: RA
authors.lastname: Felder
mesh_terms: D000704:Analysis of Variance; D051242:Caveolin 1 / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D018818:Fenoldopam / Q000494:pharmacology*; D054771:G-Protein-Coupled Receptor Kinase 4 / Q000032:analysis / Q000378:metabolism; D006801:Humans; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000187:drug effects*; D018613:Microscopy, Confocal; D011336:Probability; D017447:Receptors, Dopamine D1 / Q000187:drug effects / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000187:drug effects / Q000378:metabolism*
chemical_list: D051242:Caveolin 1; D017447:Receptors, Dopamine D1; D000242:Cyclic AMP; D054771:G-Protein-Coupled Receptor Kinase 4; D000254:Sodium-Potassium-Exchanging ATPase; D018818:Fenoldopam