title: Dopamine recruits D1A receptors to Na-K-ATPase-rich caveolar plasma membranes in rat renal proximal tubules.
abstract: Activation of dopamine D(1A) receptors in renal proximal tubules causes inhibition of sodium transporters (Na-K-ATPase and Na/H exchanger), leading to a decrease in sodium reabsorption. In addition to being localized on the plasma membrane, D(1A) receptors are mainly present in intracellular compartments under basal conditions. We observed, using [(3)H]SCH-23390 binding and immunoblotting, that dopamine recruits D(1A) receptors to the plasma membrane in rat renal proximal tubules. Furthermore, radioligand binding and/or immunoblotting experiments using pharmacological modulators showed that dopamine-induced D(1A) receptor recruitment requires activation of cell surface D(1)-like receptors, activation of adenylyl cyclase, and intact endocytic vesicles with internal acidic pH. A key finding of this study was that these recruited D(1A) receptors were functional because they potentiated dopamine-induced [(35)S]GTPgammaS binding, cAMP accumulation, and Na-K-ATPase inhibition. Interestingly, dopamine increased immunoreactivity of D(1A) receptors specifically in caveolin-rich plasma membranes isolated by a sucrose density gradient. In support of this observation, coimmunoprecipitation studies showed that D(1A) receptors interacted with caveolin-2 in an agonist-dependent fashion. The caveolin-rich plasma membranes had a high content of the alpha(1)-subunit of Na-K-ATPase, which is a downstream target of D(1A) receptor signaling in proximal tubules. These results show that dopamine, via the D(1)-like receptor-adenylyl cyclase pathway, recruits D(1A) receptors to the plasma membrane. These newly recruited receptors couple to G proteins, increase cAMP, and participate in dopamine-mediated inhibition of Na-K-ATPase in proximal tubules. Moreover, dopamine-induced recruitment of D(1A) receptors to the caveolin-rich plasma membranes brings them in close proximity to targets such as Na-K-ATPase in proximal tubules of Sprague-Dawley rats.
authors.affiliation: Heart and Kidney Institute, College of Pharmacy, University of Houston, Houston, TX 77204-5041, USA.
authors.forename: Meghna
authors.initials: M
authors.lastname: Trivedi
authors.forename: Vihang A
authors.initials: VA
authors.lastname: Narkar
authors.forename: Tahir
authors.initials: T
authors.lastname: Hussain
authors.forename: Mustafa F
authors.initials: MF
authors.lastname: Lokhandwala
mesh_terms: D000818:Animals; D001552:Benzazepines; D015153:Blotting, Western; D002462:Cell Membrane / Q000201:enzymology*; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D004298:Dopamine / Q000502:physiology*; D018492:Dopamine Antagonists; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000201:enzymology*; D018942:Macrolides / Q000494:pharmacology; D008297:Male; D008871:Microvilli / Q000378:metabolism; D011233:Precipitin Tests; D011869:Radioligand Assay; D051381:Rats; D017207:Rats, Sprague-Dawley; D017447:Receptors, Dopamine D1 / Q000378:metabolism*; D015290:Second Messenger Systems / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
chemical_list: D001552:Benzazepines; D018492:Dopamine Antagonists; D004791:Enzyme Inhibitors; D018942:Macrolides; D017447:Receptors, Dopamine D1; D017923:Sodium-Hydrogen Exchangers; C098593:dopamine D1A receptor; D005576:Colforsin; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C040929:bafilomycin A1; D000242:Cyclic AMP; D019204:GTP-Binding Proteins; D000254:Sodium-Potassium-Exchanging ATPase; D004298:Dopamine