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XB-ART-55798
Clin Exp Nephrol 2019 Jul 01;237:898-907. doi: 10.1007/s10157-019-01725-6.
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Role of the putative PKC phosphorylation sites of the type IIc sodium-dependent phosphate transporter in parathyroid hormone regulation.

Fujii T , Segawa H , Hanazaki A , Nishiguchi S , Minoshima S , Ohi A , Tominaga R , Sasaki S , Tanifuji K , Koike M , Arima Y , Shiozaki Y , Kaneko I , Ito M , Tatsumi S , Miyamoto KI .


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BACKGROUND: Injection of parathyroid hormone (PTH) rapidly stimulates renal Pi excretion, in part by downregulating NaPi-IIa (Npt2a/SLC34A1) and NaPi-IIc (Npt2c/SLC34A3) transporters. The mechanisms underlying the effects of PTH on NaPi-IIc are not fully elucidated. METHODS: We analyzed the effect of PTH on inorganic phosphate (Pi) reabsorption in Npt2a-/- mice to eliminate the influence of Npt2a on renal Pi reabsorption. In opossum kidney (OK) cells and Xenopus oocytes, we investigated the effect of NaPi-IIc transporter phosphorylation. Studies of mice with mutations of NaPi-IIc protein in which serine and threonine were replaced with either alanine (A), which prevents phosphorylation, or aspartic acid (D), which mimics the charged state of phosphorylated NaPi-IIc, were also performed to evaluate the involvement of phosphorylation in the regulation of transport function. RESULTS: The Npt2a-/- experiments showed that PTH administration rapidly inactivated NaPi-IIc function in the apical membrane of proximal tubular cells. Analysis of mutant proteins (S71, S138, T151, S174, T583) at putative protein kinase C sites, revealed that S138 markedly suppressed the function and cellular expression of mouse NaPi-IIc in Xenopus oocytes and OK cells. In addition, 138D had a short half-life compared with wild-type protein. CONCLUSIONS: The present study suggests that acute regulation of NaPi-IIc protein by PTH is involved in the inactivation of Na+-dependent Pi cotransporter activity and that phosphorylation of the transporter is involved in the rapid modification.

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Species referenced: Xenopus
Genes referenced: pth

References [+] :
Beck, Targeted inactivation of Npt2 in mice leads to severe renal phosphate wasting, hypercalciuria, and skeletal abnormalities. 1998, Pubmed