Dopamine regulation of Na⁺-K⁺-ATPase requires the PDZ-2 domain of sodium hydrogen regulatory factor-1 (NHERF-1) in opossum kidney cells

Na⁺-K⁺-ATPase activity in renal proximal tubule is regulated by several hormones including parathyroid hormone (PTH) and dopamine. The current experiments explore the role of Na⁺/H⁺ exchanger regulatory factor 1 (NHERF-1) in dopamine-mediated regulation of Na⁺-K⁺-ATPase. We measured dopamine regulation of ouabain-sensitive ⁸⁶Rb uptake and Na⁺-K⁺-ATPase α1 subunit phosphorylation in wild-type opossum kidney (OK) (OK-WT) cells, OKH cells (NHERF-1-deficient), and OKH cells stably transfected with full-length human NHERF-1 (NF) or NHERF-1 constructs with mutated PDZ-1 (Z1) or PDZ-2 (Z2) domains. Treatment with 1 μM dopamine decreased ouabain-sensitive ⁸⁶Rb uptake, increased phosphorylation of Na⁺-K ⁺-ATPase α1-subunit, and enhanced association of NHERF-1 with D1 receptor in OK-WT cells but not in OKH cells. Transfection with wild-type, full-length, or PDZ-1 domain-mutated NHERF-1 into OKH cells restored dopamine-mediated regulation of Na⁺-K⁺-ATPase and D1-like receptor association with NHERF-1. Dopamine did not regulate Na ⁺-K⁺-ATPase or increase D1-like receptor association with NHERF-1 in OKH cells transfected with mutated PDZ-2 domain. Dopamine stimulated association of PKC-ζ with NHERF-1 in OK-WT and OKH cells transfected with full-length or PDZ-1 domain-mutated NHERF-1 but not in PDZ-2 domain-mutated NHERF-1-transfected OKH cells. These results suggest that NHERF-1 mediates Na⁺-K⁺-ATPase regulation by dopamine through its PDZ-2 domain.