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1 Medicine, University of Maryland School of Medicine, Baltimore, Maryland, United States
2 Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina, United States
3 Medicine, University of Maryland School of Medicine, Baltimore, Maryland, United States; Physiology, University of Maryland School of Medicine, Baltimore, Maryland, United States; Physiology, University of Maryland School of Medicine, Baltimore, Maryland, United States
* To whom correspondence should be addressed. E-mail: eweinman{at}medicine.umaryland.edu.
Sodium-dependent phosphate transport in NHERF-1-/- proximal tubule cells does not increase when grown in a low phosphate media and are resistant to the normal inhibitory effects of parathyroid hormone (PTH). The current experiments employ adenovirus-mediated gene transfer in primary cultures of mouse proximal tubule cells from NHERF-1 null mice to explore the specific role of NHERF-1 on regulated Npt2a trafficking and sodium-dependent phosphate transport. NHERF-1 null cells have decreased sodium-dependent phosphate transport compared to wild-type cells. Infection of NHERF-1 null cells with adenovirus-GFP-NHERF-1 increased phosphate transport and plasma membrane abundance of Npt2a. Adenovirus-GFP-NHERF-1 infected NHERF-1 null proximal tubule cells but not cells infected with adenovirus-GFP demonstrated increased phosphate transport and Npt2a abundance in the plasma membrane when grown in low phosphate (0.1 mM) as compared to high phosphate media (1.9 mM). PTH inhibited phosphate transport and decreased Npt2a abundance in the plasma membrane of adenovirus-GFP-NHERF-1 infected NHERF-1 null proximal tubule cells but not cells infected with adenovirus-GFP. Interestingly, phosphate transport is inhibited by activation of protein kinase A and protein kinase C in wild-type proximal tubule cells but not in NHERF-1-/- cells. Together, these results highlight the requirement for NHERF-1 for physiological control of Npt2a trafficking and suggest that the Npt2a/NHERF-1 complex represents a unique PTH-responsive pool of Npt2a in renal microvilli.
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