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

Breusegem SY, Takahashi H, Giral-Arnal H, Wang X, Jiang T, Verlander JW, Wilson P, Miyazaki-Anzai S, Sutherland E, Caldas Y, Blaine JT, Segawa H, Miyamoto K, Barry NP, Levi M - Am. J. Physiol. Renal Physiol. (2009)

Bottom Line: Dietary potassium (K) deficiency is accompanied by phosphaturia and decreased renal brush border membrane (BBM) vesicle sodium (Na)-dependent phosphate (P(i)) transport activity.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 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.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, Division of Renal Diseases and Hypertension, University of Colorado Denver, Aurora, Colorado, USA. syab2@cam.ac.uk

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.

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Transmission electron micrographs illustrating NaPi-IIc immunolabel in lysosomes of S1 segment proximal tubule cells from control (a–c) and K-deficient (d–f) rats. In a (control) and d (K deficient), areas containing lysosomes (L) are denoted by white rectangles and illustrated at high magnification in subsequent panels, with correlating letters (control, b and c; K deficient, e and f). In control rats, only occasional gold particles were found in lysosomes (b, arrows) or in small vesicles in the vicinity of lysosomes (c, arrowhead), whereas the majority of lysosomes were not labeled (c). In K-deficient rats, NaPi-IIc immunolabel was more prevalent in lysosomes (e and f, arrows) compared with control rats.
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f9: Transmission electron micrographs illustrating NaPi-IIc immunolabel in lysosomes of S1 segment proximal tubule cells from control (a–c) and K-deficient (d–f) rats. In a (control) and d (K deficient), areas containing lysosomes (L) are denoted by white rectangles and illustrated at high magnification in subsequent panels, with correlating letters (control, b and c; K deficient, e and f). In control rats, only occasional gold particles were found in lysosomes (b, arrows) or in small vesicles in the vicinity of lysosomes (c, arrowhead), whereas the majority of lysosomes were not labeled (c). In K-deficient rats, NaPi-IIc immunolabel was more prevalent in lysosomes (e and f, arrows) compared with control rats.

Mentions: Gold labeling was also found in lysosomes (black arrows) and in small vesicles associated with lysosomes (black arrowheads) more frequently in K-deficient rats (Fig. 9 b) than in the control animals (Fig. 9a).


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

Breusegem SY, Takahashi H, Giral-Arnal H, Wang X, Jiang T, Verlander JW, Wilson P, Miyazaki-Anzai S, Sutherland E, Caldas Y, Blaine JT, Segawa H, Miyamoto K, Barry NP, Levi M - Am. J. Physiol. Renal Physiol. (2009)

Transmission electron micrographs illustrating NaPi-IIc immunolabel in lysosomes of S1 segment proximal tubule cells from control (a–c) and K-deficient (d–f) rats. In a (control) and d (K deficient), areas containing lysosomes (L) are denoted by white rectangles and illustrated at high magnification in subsequent panels, with correlating letters (control, b and c; K deficient, e and f). In control rats, only occasional gold particles were found in lysosomes (b, arrows) or in small vesicles in the vicinity of lysosomes (c, arrowhead), whereas the majority of lysosomes were not labeled (c). In K-deficient rats, NaPi-IIc immunolabel was more prevalent in lysosomes (e and f, arrows) compared with control rats.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2724260&req=5

f9: Transmission electron micrographs illustrating NaPi-IIc immunolabel in lysosomes of S1 segment proximal tubule cells from control (a–c) and K-deficient (d–f) rats. In a (control) and d (K deficient), areas containing lysosomes (L) are denoted by white rectangles and illustrated at high magnification in subsequent panels, with correlating letters (control, b and c; K deficient, e and f). In control rats, only occasional gold particles were found in lysosomes (b, arrows) or in small vesicles in the vicinity of lysosomes (c, arrowhead), whereas the majority of lysosomes were not labeled (c). In K-deficient rats, NaPi-IIc immunolabel was more prevalent in lysosomes (e and f, arrows) compared with control rats.
Mentions: Gold labeling was also found in lysosomes (black arrows) and in small vesicles associated with lysosomes (black arrowheads) more frequently in K-deficient rats (Fig. 9 b) than in the control animals (Fig. 9a).

Bottom Line: Dietary potassium (K) deficiency is accompanied by phosphaturia and decreased renal brush border membrane (BBM) vesicle sodium (Na)-dependent phosphate (P(i)) transport activity.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 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.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, Division of Renal Diseases and Hypertension, University of Colorado Denver, Aurora, Colorado, USA. syab2@cam.ac.uk

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.

Show MeSH
Related in: MedlinePlus