RESUMEN
The influence of a single gene on the pathogenesis of essential hypertension may be difficult to ascertain, unless the gene interacts with other genes that are germane to blood pressure regulation. G-protein-coupled receptor kinase type 4 (GRK4) is one such gene. We have reported that the expression of its variant hGRK4γ(142V) in mice results in hypertension because of impaired dopamine D1 receptor. Signaling through dopamine D1 receptor and angiotensin II type I receptor (AT1R) reciprocally modulates renal sodium excretion and blood pressure. Here, we demonstrate the ability of the hGRK4γ(142V) to increase the expression and activity of the AT1R. We show that hGRK4γ(142V) phosphorylates histone deacetylase type 1 and promotes its nuclear export to the cytoplasm, resulting in increased AT1R expression and greater pressor response to angiotensin II. AT1R blockade and the deletion of the Agtr1a gene normalize the hypertension in hGRK4γ(142V) mice. These findings illustrate the unique role of GRK4 by targeting receptors with opposite physiological activity for the same goal of maintaining blood pressure homeostasis, and thus making the GRK4 a relevant therapeutic target to control blood pressure.
Asunto(s)
Bencimidazoles/farmacología , Presión Sanguínea/fisiología , Quinasa 4 del Receptor Acoplado a Proteína-G/genética , Regulación de la Expresión Génica , Histona Desacetilasa 1/antagonistas & inhibidores , Hipertensión/genética , Receptor de Angiotensina Tipo 1/genética , Tetrazoles/farmacología , Bloqueadores del Receptor Tipo 1 de Angiotensina II/farmacología , Animales , Compuestos de Bifenilo , Modelos Animales de Enfermedad , Hipertensión Esencial , Femenino , Quinasa 4 del Receptor Acoplado a Proteína-G/biosíntesis , Células HEK293 , Histona Desacetilasa 1/metabolismo , Humanos , Hipertensión/tratamiento farmacológico , Hipertensión/metabolismo , Immunoblotting , Riñón/metabolismo , Riñón/patología , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , ARN/genética , Reacción en Cadena en Tiempo Real de la Polimerasa , Receptor de Angiotensina Tipo 1/biosíntesis , Receptor de Angiotensina Tipo 1/efectos de los fármacos , Reacción en Cadena de la Polimerasa de Transcriptasa InversaRESUMEN
During conditions of moderate sodium excess, the dopaminergic system regulates blood pressure and water and electrolyte balance by engendering natriuresis. Dopamine exerts its effects on dopamine receptors, including the dopamine D(3) receptor. G protein-coupled receptor kinase 4 (GRK4), whose gene locus (4p16.3) is linked to essential hypertension, desensitizes the D(1) receptor, another dopamine receptor. This study evaluated the role of GRK4 on D(3) receptor function in human proximal tubule cells. D(3) receptor co-segregated in lipid rafts and co-immunoprecipitated and co-localized in human proximal tubule cells and in proximal and distal tubules and glomeruli of kidneys of Wistar Kyoto rats. Bimolecular fluorescence complementation and confocal microscopy revealed that agonist activation of the receptor initiated the interaction between D(3) receptor and GRK4 at the cell membrane and promoted it intracellularly, presumably en route to endosomal trafficking. Of the four GRK4 splice variants, GRK4-gamma and GRK4-alpha mediated a 3- and 2-fold increase in the phosphorylation of agonist-activated D(3) receptor, respectively. Inhibition of GRK activity with heparin or knockdown of GRK4 expression via RNA interference completely abolished p44/42 phosphorylation and mitogenesis induced by D(3) receptor stimulation. These data demonstrate that GRK4, specifically the GRK4-gamma and GRK4-alpha isoforms, phosphorylates the D(3) receptor and is crucial for its signaling in human proximal tubule cells.
