PP2R2C is involved in the resensitization of the dopamine D1 receptor in human renal proximal tubule cells.

Abstract

Dopamine is important in the regulation of blood pressure, sodium balance, and renal function acting through D1‐like and D2‐like dopamine receptors. Protein phosphatase 2A (PP2A) is a heterotrimeric serine/threonine phosphatase. There is tissue specific expression of the B subunits of PP2A; human renal proximal tubule cells express B55γ (PP2R2C, γ isoform, B regulatory subunit) and PP2A B56 γ (□ isoform, B′ regulatory subunit). We have reported that dopamine D1 receptor (D1R) dephosphorylation, recycling to the cell surface membrane, and resensitization are dependent on PP2A activity (Kidney Int. 2006;70:1072–9). We aimed to determine the role of PP2R2C in the spatial and temporal events involved in the resensitization of D1R in human renal proximal tubule cells. PP2A B (entire B regulatory subunit), PP2A C (catalytic subunit) and PP2R2C subunits were found to be expressed in the cytosol of immortalized human renal proximal tubular cells by confocal microscopy (n=3). Co‐immunoprecipitation studies demonstrated that the D1R interacts with PP2A B, PP2A C and PP2R2C subunits (n=3). Treatment with the D1‐like agonist fenoldopam (FEN, 1 □M) decreased expression of PP2A B (15%; n=3) and PP2A B56γ (30%; n=3) but increased that of PP2R2C (25%: n=3). Treatment with FEN for 15 min increased total phosphatase activity (18%; n=2). Upon FEN stimulation the D1R internalized and co‐localized with of PP2R2C (n=3). These results suggest that PP2A and PP2R2C are involved in the regulation of the resensitization and trafficking of the D1R.This work was supported in part by grants from the National Institutes of Health, HL68686, HL23081, HL074940, HL092196 and DK39308