Dataset Information

Differential regulation of the renal sodium-phosphate cotransporters NaPi-IIa, NaPi-IIc, and PiT-2 in dietary potassium deficiency.

ABSTRACT: Dietary potassium (K) deficiency is accompanied by phosphaturia and decreased renal brush border membrane (BBM) vesicle sodium (Na)-dependent phosphate (P(i)) transport activity. Our laboratory previously showed that K deficiency in rats leads to increased abundance in the proximal tubule BBM of the apical Na-P(i) cotransporter NaPi-IIa, but that the activity, diffusion, and clustering of NaPi-IIa could be modulated by the altered lipid composition of the K-deficient BBM (Zajicek HK, Wang H, Puttaparthi K, Halaihel N, Markovich D, Shayman J, Beliveau R, Wilson P, Rogers T, Levi M. Kidney Int 60: 694-704, 2001; Inoue M, Digman MA, Cheng M, Breusegem SY, Halaihel N, Sorribas V, Mantulin WW, Gratton E, Barry NP, Levi M. J Biol Chem 279: 49160-49171, 2004). Here we investigated the role of the renal Na-P(i) cotransporters NaPi-IIc and PiT-2 in K deficiency. Using Western blotting, immunofluorescence, and quantitative real-time PCR, we found that, in rats and in mice, K deficiency is associated with a dramatic decrease in the NaPi-IIc protein abundance in proximal tubular BBM and in NaPi-IIc mRNA. In addition, we documented the presence of a third Na-coupled P(i) transporter in the renal BBM, PiT-2, whose abundance is also decreased by dietary K deficiency in rats and in mice. Finally, electron microscopy showed subcellular redistribution of NaPi-IIc in K deficiency: in control rats, NaPi-IIc immunolabel was primarily in BBM microvilli, whereas, in K-deficient rats, NaPi-IIc BBM label was reduced, and immunolabel was prevalent in cytoplasmic vesicles. In summary, our results demonstrate that decreases in BBM abundance of the phosphate transporter NaPi-IIc and also PiT-2 might contribute to the phosphaturia of dietary K deficiency, and that the three renal BBM phosphate transporters characterized so far can be differentially regulated by dietary perturbations.

SUBMITTER: Breusegem SY

PROVIDER: S-EPMC2724260 | biostudies-literature | 2009 Aug

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Differential regulation of the renal sodium-phosphate cotransporters NaPi-IIa, NaPi-IIc, and PiT-2 in dietary potassium deficiency.

Breusegem Sophia Y SY Takahashi Hideaki H Giral-Arnal Hector H Wang Xiaoxin X Jiang Tao T Verlander Jill W JW Wilson Paul P Miyazaki-Anzai Shinobu S Sutherland Eileen E Caldas Yupanqui Y Blaine Judith T JT Segawa Hiroko H Miyamoto Ken-ichi K Barry Nicholas P NP Levi Moshe M

American journal of physiology. Renal physiology 20090603 2

Dietary potassium (K) deficiency is accompanied by phosphaturia and decreased renal brush border membrane (BBM) vesicle sodium (Na)-dependent phosphate (P(i)) transport activity. Our laboratory previously showed that K deficiency in rats leads to increased abundance in the proximal tubule BBM of the apical Na-P(i) cotransporter NaPi-IIa, but that the activity, diffusion, and clustering of NaPi-IIa could be modulated by the altered lipid composition of the K-deficient BBM (Zajicek HK, Wang H, Put ...[more]

PMID: 19493963

Similar Datasets

Project description:Transporters of the SLC34 family (NaPi-IIa,b,c) catalyze uptake of inorganic phosphate (Pi) in renal and intestinal epithelia. The transport cycle requires three Na(+) ions and one divalent Pi to bind before a conformational change enables translocation, intracellular release of the substrates, and reorientation of the empty carrier. The electrogenic interaction of the first Na(+) ion with NaPi-IIa/b at a postulated Na1 site is accompanied by charge displacement, and Na1 occupancy subsequently facilitates binding of a second Na(+) ion at Na2. The voltage dependence of cotransport and presteady-state charge displacements (in the absence of a complete transport cycle) are directly related to the molecular architecture of the Na1 site. The fact that Li(+) ions substitute for Na(+) at Na1, but not at the other sites (Na2 and Na3), provides an additional tool for investigating Na1 site-specific events. We recently proposed a three-dimensional model of human SLC34a1 (NaPi-IIa) including the binding sites Na2, Na3, and Pi based on the crystal structure of the dicarboxylate transporter VcINDY. Here, we propose nine residues in transmembrane helices (TM2, TM3, and TM5) that potentially contribute to Na1. To verify their roles experimentally, we made single alanine substitutions in the human NaPi-IIa isoform and investigated the kinetic properties of the mutants by voltage clamp and (32)P uptake. Substitutions at five positions in TM2 and one in TM5 resulted in relatively small changes in the substrate apparent affinities, yet at several of these positions, we observed significant hyperpolarizing shifts in the voltage dependence. Importantly, the ability of Li(+) ions to substitute for Na(+) ions was increased compared with the wild-type. Based on these findings, we adjusted the regions containing Na1 and Na3, resulting in a refined NaPi-IIa model in which five positions (T200, Q206, D209, N227, and S447) contribute directly to cation coordination at Na1.

Dataset Information

Differential regulation of the renal sodium-phosphate cotransporters NaPi-IIa, NaPi-IIc, and PiT-2 in dietary potassium deficiency.

Publications

Differential regulation of the renal sodium-phosphate cotransporters NaPi-IIa, NaPi-IIc, and PiT-2 in dietary potassium deficiency.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets