Abstract 296: Sorting Nexin 19: A Novel Regulator of Renal Dopamine D1 Receptor
The D1 dopamine receptor (D1R) plays a pivotal role in blood pressure regulation. The present study aimed to demonstrate the role of sorting nexin 19 (SNX19) in the regulation of renal D1R trafficking and signaling. We tested the dynamic interaction between these proteins and showed that SNX19 coimmunoprecipitated with the D1R, as well as with GRK4 and β-arrestin--proteins that are required for D1R homologous desensitization, in human renal proximal tubule cells (hPRTCs) and mouse kidney homogenates. These proteins colocalized basally at the cell membrane in hRPTCs, while treatment with the D1R/D5R agonist fenoldopam (Fen) promoted their endocytosis to the juxtanuclear area, indicating that SNX19 is involved in the agonist-activated D1R trafficking. SNX19 silencing in hPRTCs reduced the D1R abundance (non-silencing “mock” siRNA=1.0±0.05 vs. Snx19-specific siRNA=0.45±0.06, P<0.05, n=3/group), although D1R depletion did not affect SNX19 expression. SNX19 depletion also blunted the cAMP response after Fen treatment (1μM, 15min) (mock: basal=12.4±4.5 pmol/mg protein vs. mock+Fen=147.8±3.4; Snx19 siRNA: basal=6.8±3.4 vs. siRNA+Fen=63.1±5.4, P<0.05, n=4). Moreover, SNX19 depletion impaired the sodium transport in response to Fen treatment (1μM, 15min) (mock: Δ intracellular Na+ from basal=+15.4±3.2%, vs. Snx19 siRNA: Δ Na+=+3.3±7.5%,P<0.05, n=3). SNX19 and D1R colocalized at the brush border in mouse and human renal proximal tubules at the basal state. Stimulation D1-like receptors in mouse kidneys with the intravenous infusion of Fen (2 μg/kg/hr, 15 min) promoted D1R internalization with SNX19 and enhanced their colocalization at the cytoplasm. Relative to control mice, the renal selective silencing of Snx19 in C57Bl/6J mice increased the systolic blood pressure (before injection: mock=100±5 mmHg vs. Snx19 siRNA=102±2; after injection: mock=101±6 vs. Snx19 siRNA=118±5, P<0.05, n=5), and decreased renal D1R expression (mock=1.0±0.09 vs. Snx19 siRNA=0.57±0.17, P<0.05, n=5). Our results indicate that SNX19 is crucial to normal D1R function and that loss of renal SNX19 results in renal D1R deficiency and dysfunction. Our data suggest that the absence of SNX19 may be a novel mechanism for the pathogenesis of essential hypertension.
Author Disclosures: J. Yang: None. V.A. Villar: None. J.E. Jones: None. Y. Guo: None. L.D. Asico: None. I. Armando: None. E.J. Weinman: None. P.A. Jose: None.
- © 2014 by American Heart Association, Inc.