Regulation of Sodium-Dependent Phosphate Transport by Parathyroid Hormone in Opossum Kidney Cells: Adenosine 3 ′,5 ′-Monophosphate-Dependent and -Independent Mechanisms*

Cole, Jon C.; Forte, Leonard R.; Eber, Sammy L.; Thorne, Pamela K.; Poelling, R. E.

doi:10.1210/endo-122-6-2981

Cited by 70 publications

(40 citation statements)

References 25 publications

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“…Opossum kidney cells retain the proximal tubular characteristics of PTH-induced regulation of brush-border membrane NaPi cotransport, associated with membrane retrieval and lysosomal degradation of type IIa NaPi cotransporters (10,11,(16)(17)(18)(30)(31)(32)(33). As a similar regulatory behavior was observed for the intrinsic (NaPi-4) and transfected (NaPi-2) transporter (10,11,14,19), OK cells represent an ideal in vitro system to study molecular determinants responsible for PTH-induced downregulation of the type IIa NaPi cotransporter.…”

Section: Resultsmentioning

confidence: 92%

“…These PTH-induced regulations are retained in cultured opossum kidney (OK) cells for both the endogenous (NaPi-4) and the transfected rat (NaPi-2) type IIa NaPi cotransporter (10)(11)(12)(13)(14). In proximal tubules and in OK cells, two signaling pathways are involved in PTH-induced downregulation of P i transport and of type IIa NaPi cotransporter: protein kinase A and protein kinase C (15)(16)(17)(18)(19). The mechanisms by which these kinase activities affect the cotransporter are not known.…”

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confidence: 99%

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A dibasic motif involved in parathyroid hormone-induced down-regulation of the type IIa NaPi cotransporter

Karim

Hernando

Biber

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

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Type II NaPi cotransporters are expressed in the apical membrane of Pi-(re)absorbing epithelia: the type IIa in renal proximal tubule and the type IIb in small intestine. Parathyroid hormone (PTH) leads to a retrieval from the apical membrane of the type IIa NaPi cotransporter. The type IIa cotransporter is also expressed in opossum kidney (OK) cells, and its expression is under the control of PTH. In the present study, we identified the molecular ''domains'' involved in the PTH-induced retrieval of the type IIa NaPi cotransporter. Wild-type mouse type IIa (mIIa) and type IIb (mIIb) as well as several mIIa-mIIb chimeras and site-directed mutants were fused to the enhanced green fluorescent protein and transfected into OK cells. We found that mIIa but not mIIb was internalized and degraded after incubation with 1-34 (or 3-34) PTH. Using chimeras, we found that the N and C termini were not required in this effect, whereas a ''domain'' located between residues 216 and 658 seemed to be necessary. This region contains two putative intracellular loops with highly conserved sequences between mIIa and mIIb; in the last intracellular loop, two charged amino acids of type IIa (K 503R504) are replaced by uncharged residues in type IIb (N520I521). We generated two mutants in which these residues were interchanged: mIIaNI and mIIbKR. Similarly to mIIa, the mIIbKR mutant was endocytosed in response to 1-34 PTH; in contrast, mIIaNI behaved as mIIb and was not internalized. In conclusion, a dibasic amino acid motif (K 503R504) located in the last intracellular loop of the type IIa NaPi cotransporter is essential for its PTH-induced retrieval.PTH ͉ endocytosis R egulated P i reabsorption in the renal proximal tubule is an important element in overall P i homeostasis. Its rate is mainly controlled by the amount of type IIa NaPi cotransporters expressed in the brush-border membrane of proximal tubular cells (1-4).Parathyroid hormone (PTH) is the main phosphaturic hormone (5). PTH exerts its effect by an inhibition of proximal tubular brush-border NaPi cotransport associated with a membrane retrieval and lysosomal degradation of type IIa NaPi cotransporters (4, 6-9). These PTH-induced regulations are retained in cultured opossum kidney (OK) cells for both the endogenous (NaPi-4) and the transfected rat (NaPi-2) type IIa NaPi cotransporter (10)(11)(12)(13)(14). In proximal tubules and in OK cells, two signaling pathways are involved in PTH-induced downregulation of P i transport and of type IIa NaPi cotransporter: protein kinase A and protein kinase C (15-19). The mechanisms by which these kinase activities affect the cotransporter are not known.The small intestinal brush-border membrane contains the type IIb NaPi cotransporter, identified in a procedure based on homology to IIa (20). Type IIa and type IIb NaPi cotransporters differ in several properties such as tissue distribution (20-22), pH sensitivity (1, 20, 23), and Na ϩ and P i kinetics (1,20,24). Type IIa and type IIb NaPi cotransporters are differently regulated; the type I...

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Section: Resultsmentioning

confidence: 92%

mentioning

confidence: 99%

A dibasic motif involved in parathyroid hormone-induced down-regulation of the type IIa NaPi cotransporter

Karim

Hernando

Biber

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

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“…PTH stimulates intestinal Ca transport indirectly through stimulation of 1,25 (OH)2D3 synthesis in proximal tubule cells. PTH-stimulated 1,25(OH)2D3 biosynthesis has been studied extensively in experimental animals in vivo (2)(3)(4)(5) and in vitro (6)(7)(8)(9)(10) using kidney slices, homogenates, and isolated tubule cells.…”

Section: Introductionmentioning

confidence: 99%

“…Several lines of evidence suggest that cAMP-mediated events are important as effectors of PTH stimulation of l-OHase activity, including: PTH increases proximal tubule cAMP production ( 17,18); infusion of cAMP into vitamin D-deficient rats increases conversion of tritium-labeled 25-hydroxyvitamin D3 (25 OHD3) to 1,25 (OH )2D3 ( 19); and in vitro addition ofcAMP and its dibutyryl analogue increase proximal tubule 1,25 (OH)2D3 synthesis and 1-OHase activity (6,(11)(12)(13).…”

Section: Introductionmentioning

confidence: 99%

“…These effectors elevate cytosolic Ca ( 18,23) and activate protein kinase C (PKC) (24). Second, there is a several log dose disparity between the dose of PTH that causes half-maximal inhibition of proximal tubule Na-dependent phosphate transport and the half-maximal stimulation of cAMP production (25,26 (30). In the present study, direct measurements of PKC and PKA activities, their dose-dependent activation by PTH and highly selective inhibition of PKC were used to explore the role of the cAMP/PKA ( 31 ).…”

Section: Introductionmentioning

confidence: 99%

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Role of protein kinase C in parathyroid hormone stimulation of renal 1,25-dihydroxyvitamin D3 secretion.

Janulis¹,

Tembe²,

Favus³

1992

J. Clin. Invest.

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PTH is a major regulator of renal proximal tubule 1,25(OH)2D3 biosynthesis. However, the intracellular pathways involved in PTH activation of the mitochondrial 25-hydroxyvitamin D3-1 alpha-hydroxylase (1-OHase) remain unknown. PTH can activate both the adenylate cyclase/protein kinase A (PKA) and the plasma membrane phospholipase C/ protein kinase C (PKC) pathways. The present study was undertaken to determine whether PKC may mediate PTH activation of renal 25-hydroxyvitamin D3-1 alpha-hydroxylase activity. Rat PTH 1-34 fragment in vitro translocated PKC activity from cytosolic to soluble membrane fraction from freshly prepared rat proximal tubules. Physiologic concentrations (10-'-10-10 M) of rat PTH 1-34 fragment increased PKC translocation three-to fourfold while PKA activity ratio increased at PTH i0 -M. PTH stimulation of PKC and PKA was reduced in the presence of staurosporine (10 nM) by 41 and 29%, respectively. Sangivamycin (10 and 50 ,M) also reduced PTHstimulated PKC translocation, but did not alter PKA activity ratio.In vitro perifusion of renal proximal tubules with PTH (1011 M) increased 1,25(OH)2D3 steady-state secretion twoto fourfold. Sangivamycin at the same concentration that inhibited PKC translocation by 52% completely inhibited PTHstimulated 1,25(OH)2D3 secretion. The present studies indicate that the phospholipase C/PKC pathway may mediate PTH stimulation of mammalian renal proximal tubule 1,25(OH)2D3 secretion. (J. Clin. Invest. 1992. 90:2278-2283

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Dog and rat kidney proximal tubule cells in culture: Responses to parathyroid hormone

Rao

Yau

Kovács

1989

Journal of Bone and Mineral Research

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We have described and compared culture systems for proximal tubule cell (PTC) preparations from dog and rat kidney. Cells were prepared from kidney cortex by enzyme digestion and purified on Percoll density gradient. The dog PTC and rat PTC differed in their growth characteristics in culture. Although the dog PTC tended to overgrow the contaminating fibroblastic cells, the rat PTC tended to be overgrown by the latter cells when cultured in medium containing 15% fetal calf serum (FCS). Cultures of rat PTC in serum-free medium or medium containing only 2% FCS yielded only epithelium-like cells exhibiting characteristics of cells that are proximal tubular in origin. These properties include protrusion of microvilli, high alkaline phosphatase activity, ability to transport sugar, and responsiveness to parathyroid hormone (PTH) in terms of cAMP production. The time course and dose-response curves of PTH-stimulated cAMP accumulation were studied in dog and rat PTC. The estimated half-maximal concentrations (Kact) for PTH in dog and rat PTC were 1.2 and 100 nM, respectively. Both values are within the range reported in the literature for the respective renal membrane preparations. In addition to our previously reported data on dog PTC, this study revealed the presence of PTH-inhibitable 25-hydroxyvitamin D3-24-hydroxylase in dog PTC. These two model cell culture systems should prove useful in studying PTH action in renal cells.

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Regulation of Sodium-Dependent Phosphate Transport by Parathyroid Hormone in Opossum Kidney Cells: Adenosine 3 ′,5 ′-Monophosphate-Dependent and -Independent Mechanisms*

Cited by 70 publications

References 25 publications

A dibasic motif involved in parathyroid hormone-induced down-regulation of the type IIa NaPi cotransporter

A dibasic motif involved in parathyroid hormone-induced down-regulation of the type IIa NaPi cotransporter

Role of protein kinase C in parathyroid hormone stimulation of renal 1,25-dihydroxyvitamin D3 secretion.

Dog and rat kidney proximal tubule cells in culture: Responses to parathyroid hormone

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