title: Gialpha3 protein-coupled dopamine D3 receptor-mediated inhibition of renal NHE3 activity in SHR proximal tubular cells is a PLC-PKC-mediated event.
abstract: This study evaluated the transduction pathway associated with type 3 Na(+)/H(+) exchanger (NHE3) activity-induced inhibition during dopamine D(3) receptor activation in immortalized renal proximal tubular epithelial cells from the spontaneously hypertensive rat. The dopamine D(3) receptor agonist 7-OH-DPAT decreased NHE3 activity, which was prevented by the D(2)-like receptor antagonist S-sulpiride, pertussis toxin (PTX; overnight treatment), and the PKC inhibitor chelerythrine, but not by cholera toxin (overnight treatment), the MAPK inhibitor PD-098059, or the p38 inhibitor SB-203580. The PKA inhibitor H-89 abolished the inhibitory effects of forskolin on NHE3 activity, but not that of 7-OH-DPAT. The phospholipase C (PLC) inhibitor U-73122 prevented the inhibitory effects of 7-OH-DPAT, whereas PDBu and 7-OH-DPAT increased PLC activity and reduced NHE3 activity; downregulation of PKC abolished the inhibitory effects of both PDBu and 7-OH-DPAT on NHE activity. The inhibition of NHE3 activity by GTPgammaS and the prevention of the effect of 7-OH-DPAT by PTX suggest an involvement of a G(i/o) protein coupled to the dopamine D(3) receptor. Indeed, the 7-OH-DPAT-induced decrease in NHE3 activity was abolished in cells treated overnight with the anti-G(i)alpha3 antibody, but not in cells treated with antibodies against G(q/11), G(s)alpha, G(beta), and G(i)alpha1,2 proteins. The calcium ionophore A-23187 and the Ca(2+)-ATPase inhibitor thapsigargin increased intracellular Ca(2+) but did not affect NHE3 activity. However, the inhibitory effects of PDBu and 7-OH-DPAT on NHE3 activity were completely abolished by A-23287 and thapsigargin. It is concluded that inhibition of NHE3 activity by dopamine D(3) receptors coupled to G(i)alpha3 proteins is a PLC-PKC-mediated event, modulated by intracellular Ca(2+).
authors.affiliation: Institute of Pharmacology and Therapeutics, Faculty of Medicine, 4200-319 Porto, Portugal.
authors.forename: Rui
authors.initials: R
authors.lastname: Pedrosa
authors.forename: Pedro
authors.initials: P
authors.lastname: Gomes
authors.forename: Ulrich
authors.initials: U
authors.lastname: Hopfer
authors.forename: Pedro A
authors.initials: PA
authors.lastname: Jose
authors.forename: Patrício
authors.initials: P
authors.lastname: Soares-da-Silva
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000502:physiology; D002460:Cell Line; D002772:Cholera Toxin / Q000494:pharmacology; D018492:Dopamine Antagonists / Q000494:pharmacology; D015536:Down-Regulation / Q000502:physiology; D005419:Flavonoids / Q000494:pharmacology; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000502:physiology*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000201:enzymology*; D037342:Pertussis Toxin / Q000494:pharmacology; D011493:Protein Kinase C / Q000502:physiology*; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D011918:Rats, Inbred SHR; D017448:Receptors, Dopamine D2 / Q000502:physiology*; D050637:Receptors, Dopamine D3; D043562:Receptors, G-Protein-Coupled / Q000502:physiology*; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013469:Sulpiride / Q000494:pharmacology; D013764:Tetrahydronaphthalenes / Q000494:pharmacology; D010738:Type C Phospholipases / Q000502:physiology*
chemical_list: D018492:Dopamine Antagonists; C493595:Drd3 protein, rat; D005419:Flavonoids; D007093:Imidazoles; D011725:Pyridines; D017448:Receptors, Dopamine D2; D050637:Receptors, Dopamine D3; D043562:Receptors, G-Protein-Coupled; C000613387:Slc9a3 protein, rat; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; D013764:Tetrahydronaphthalenes; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D013469:Sulpiride; D002772:Cholera Toxin; D037342:Pertussis Toxin; D011493:Protein Kinase C; D010738:Type C Phospholipases; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; C498820:Gnai3 protein, rat; C093642:SB 203580; C031349:7-hydroxy-2-N,N-dipropylaminotetralin; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; D002118:Calcium