Abstract 16723: Dopamine D3 Receptor Decreases NHE3 Expression and Function by Inhibiting the Activity of the De-Ubiquitinylating Enzyme, USP48, in Renal Proximal Tubule Cells

Disruption of the dopamine D3 receptor gene in mice (D3R-/-) results in high blood pressure, salt sensitivity, decreased ability to excrete a sodium load and increased renal expression of sodium/hydrogen exchanger isoform 3 (NHE3) protein (180%, P<0.05) but not mRNA, and D3R blockade in wild-type mice increased (2 fold, P<0.04) NHE3 protein expression. We hypothesized that renal D3R regulates NHE3 expression/function. In human renal proximal tubular cells (hRPTCs), the colocalization and co-immunoprecipitation of D3R and NHE3 are increased by D3R stimulation (PD 128907, 1μM), associated to internalization of D3R and NHE3 (confocal microscopy) and inhibition (80%, P<0.05) of NHE3 dependent Na+ transport. D3R stimulation also increases NHE3 ubiquitinylation and internalization of the ubiquitinylated NHE3 in the cytoplasm (150%, P<0.05) suggesting that D3R activation promotes NHE3 ubiquitinylation and internalization. To determine the mechanism of the D3R-mediated NHE3 ubiquitinylation we performed a yeast-t...