title: Acute regulation of renal Na+/H+ exchanger NHE3 by dopamine: role of protein phosphatase 2A.
abstract: Nephrogenic dopamine is a potent natriuretic paracrine/autocrine hormone that is central for mammalian sodium homeostasis. In the renal proximal tubule, dopamine induces natriuresis partly via inhibition of the sodium/proton exchanger NHE3. The signal transduction pathways and mechanisms by which dopamine inhibits NHE3 are complex and incompletely understood. This manuscript describes the role of the serine/threonine protein phosphatase 2A (PP2A) in the regulation of NHE3 by dopamine. The PP2A regulatory subunit B56δ (coded by the Ppp2r5d gene) directly associates with more than one region of the carboxy-terminal hydrophilic putative cytoplasmic domain of NHE3 (NHE3-cyto), as demonstrated by yeast-two-hybrid, coimmunoprecipitation, blot overlay, and in vitro pull-down assays. Phosphorylated NHE3-cyto is a substrate for purified PP2A in an in vitro dephosphorylation reaction. In cultured renal cells, inhibition of PP2A by either okadaic acid or by overexpression of the simian virus 40 (SV40) small T antigen blocks the ability of dopamine to inhibit NHE3 activity and to reduce surface NHE3 protein. Dopamine-induced NHE3 redistribution is also blocked by okadaic acid ex vivo in rat kidney cortical slices. These studies demonstrate that PP2A is an integral and critical participant in the signal transduction pathway between dopamine receptor activation and NHE3 inhibition.
authors.affiliation: Dept. of Internal Medicine, Div. of Nephrology, Univ. of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390-8856, USA.
authors.forename: I Alexandru
authors.initials: IA
authors.lastname: Bobulescu
authors.forename: Henry
authors.initials: H
authors.lastname: Quiñones
authors.forename: Serge M
authors.initials: SM
authors.lastname: Gisler
authors.forename: Francesca
authors.initials: F
authors.lastname: Di Sole
authors.forename: Ming-Chang
authors.initials: MC
authors.lastname: Hu
authors.forename: Mingjun
authors.initials: M
authors.lastname: Shi
authors.forename: Jianning
authors.initials: J
authors.lastname: Zhang
authors.forename: Daniel G
authors.initials: DG
authors.lastname: Fuster
authors.forename: Nancy
authors.initials: N
authors.lastname: Wright
authors.forename: Marc
authors.initials: M
authors.lastname: Mumby
authors.forename: Orson W
authors.initials: OW
authors.lastname: Moe
mesh_terms: D000818:Animals; D000952:Antigens, Polyomavirus Transforming / Q000494:pharmacology; D002478:Cells, Cultured; D004298:Dopamine / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D023421:Models, Animal; D019319:Okadaic Acid / Q000494:pharmacology; D009893:Opossums; D054648:Protein Phosphatase 2 / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*
chemical_list: D000952:Antigens, Polyomavirus Transforming; D004791:Enzyme Inhibitors; C000613387:Slc9a3 protein, rat; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; D019319:Okadaic Acid; D054648:Protein Phosphatase 2; D004298:Dopamine