Novel role of sorting nexin 5 in renal D ₁ dopamine receptor trafficking and function: implications for hypertension

Abstract

The D1 dopamine receptor (D1R) is widely expressed in the kidney and plays a crucial role in blood pressure regulation. Although much is known about D1R desensitization, especially through G-protein-coupled receptor kinase 4 (GRK4), comparatively little is known about other aspects of D1R trafficking and the proteins involved in the process. We now report the discovery of a dynamic interaction between sorting nexin 5 (SNX5), a component of the mammalian retromer, and D1R in human renal epithelial cells. We show that internalization of agonist-activated D1R is regulated by both SNX5 and GRK4, and that SNX5 is critical to the recycling of the receptor to the plasma membrane. SNX5 depletion increases agonist-activated D1R phosphorylation (>50% at basal condition), prevents D1R internalization and cAMP response, and delays receptor recycling compared to mock siRNA-transfected controls. Moreover, renal restricted subcapsular infusion of Snx5-specific siRNA (vs. mock siRNA) decreases sodium excretion (Δ=-0.2±0.005 mEq/mg creatinine) and further elevates the systolic blood pressure (Δ=48±5 mm Hg) in spontaneously hypertensive rats, indicating that SNX5 depletion impairs renal D1R function. These studies demonstrate an essential role for SNX5 in regulating D1R function, which may have important diagnostic, prognostic, and therapeutic implications in the management of essential hypertension.

Sorting Nexin 5 and Dopamine D1 Receptor Regulate the Expression of the Insulin Receptor in Human Renal Proximal Tubule Cells

“…SNX1, SNX2, and SNX4 have been reported to regulate the cellular trafficking of receptors for epidermal growth factor, insulin, plateletderived growth factor, and leptin (15). In addition, we found that the recycling of D 5 R and D 1 R is also regulated by SNX1 and SNX5, respectively (12,16). In a separate study, we found that SNX5 also positively regulates the expression and activity of the insulin degrading enzyme; selective renal silencing of SNX5 in Wistar-Kyoto rats increases the circulating insulin levels (our unpublished data).…”

“…There was minimal colocalization of SNX5 and IR in the basal state; colocalization of SNX5 and IR in the perinuclear area increased after 15 and 30 minutes of insulin (100nM) treatment ( Figure 1C). We have previously reported that SNX5 and D 1 R colocalize and coimmunoprecipitate in hRPTCs (12). However, there was no coimmunoprecipitation between SNX5 and IR in the basal state or even after insulin (100nM/30 min) or fenoldopam (10 Ϫ6 M/30 min) treatment ( Figure 1D).…”

“…We have reported that SNX5 physically interacts with D 1 R and SNX5 is involved in D 1 R trafficking (12,16). Because the D 1 R physically Figure 6.…”

“…Once internalized, the receptors, in vesicles termed "early endosomes," are sorted by sorting nexins (SNXs) and follow divergent pathways; the receptors are either sorted into recycling endosomes for their return to the cell membrane (recycling and resensitization) or in late endosomes, which target the receptors to lysosomes or proteasomes for their subsequent degradation (12,13). The SNX family is involved in vesicular trafficking and recycling of G protein-coupled receptors (12,14,15). SNX1, SNX2, and SNX4 have been reported to regulate the cellular trafficking of receptors for epidermal growth factor, insulin, plateletderived growth factor, and leptin (15).…”

Dopamine D1-like receptors regulate the α1A-adrenergic receptor in human renal proximal tubule cells and D1-like dopamine receptor knockout mice

“…7). Agonistactivated D 1 Rs and D 5 Rs dimerize in renal epithelial cells (P. Yu and P. Jose, unpublished observations), and the impairment of one receptor results in the total absence of cAMP production in response to agonist stimulation (68,69), indicating a collaborative association between D 1 Rs and D 5 Rs. These receptors dimerize with ANG II type 2 receptors to cooperatively Fig.…”