Proximal Tubular Phosphate Reabsorption: Molecular Mechanisms

2000 ◽  
Vol 80 (4) ◽  
pp. 1373-1409 ◽  
Author(s):  
Heini Murer ◽  
Nati Hernando ◽  
Ian Forster ◽  
Jürg Biber
Keyword(s):  
Brush Border ◽  
Molecular Mechanisms ◽  
Brush Border Membrane ◽  
Cell Model ◽  
Expression System ◽  
Cellular Mechanisms ◽  
Membrane Expression ◽  
Renal Brush Border Membrane ◽  
Proximal Tubular ◽  
Renal Proximal Tubular

Renal proximal tubular reabsorption of Pi is a key element in overall Pi homeostasis, and it involves a secondary active Pi transport mechanism. Among the molecularly identified sodium-phosphate (Na/Pi) cotransport systems a brush-border membrane type IIa Na-Pi cotransporter is the key player in proximal tubular Pi reabsorption. Physiological and pathophysiological alterations in renal Pi reabsorption are related to altered brush-border membrane expression/content of the type IIa Na-Picotransporter. Complex membrane retrieval/insertion mechanisms are involved in modulating transporter content in the brush-border membrane. In a tissue culture model (OK cells) expressing intrinsically the type IIa Na-Pi cotransporter, the cellular cascades involved in “physiological/pathophysiological” control of Pi reabsorption have been explored. As this cell model offers a “proximal tubular” environment, it is useful for characterization (in heterologous expression studies) of the cellular/molecular requirements for transport regulation. Finally, the oocyte expression system has permitted a thorough characterization of the transport characteristics and of structure/function relationships. Thus the cloning of the type IIa Na-Pi cotransporter (in 1993) provided the tools to study renal brush-border membrane Na-Pi cotransport function/regulation at the cellular/molecular level as well as at the organ level and led to an understanding of cellular mechanisms involved in control of proximal tubular Pi handling and, thus, of overall Pihomeostasis.

Characterization and distribution of albumin binding protein in normal rat kidney

1996 ◽  
Vol 271 (1) ◽  
pp. F101-F107 ◽  
Author(s):  
A. L. Cessac-Guillemet ◽  
F. Mounier ◽  
C. Borot ◽  
H. Bakala ◽  
M. Perichon ◽  
...  
Keyword(s):  
Proximal Tubule ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Binding Protein ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Albumin Binding ◽  
Renal Brush Border Membrane ◽  
Proximal Tubular ◽  
Renal Proximal Tubular

The mechanism by which proteins that pass through the glomerular basal lamina are taken up by proximal tubule cells is incompletely characterized. Past work has identified the kinetics of albumin binding to renal brush-border membrane. We have now purified and characterized albumin binding protein (ABP) and shown its distribution in renal proximal tubular cells. ABP was purified from rat renal proximal tubular cell brush-border membrane by affinity chromatography with rat serum albumin-Sepharose. The resulting ABP had two apparent molecular masses (55 and 31 kDa) by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Antibodies to ABP were raised in rabbits and checked by immunoassay and immunoblotting. Light-microscopic immunohistochemistry showed ABP all along the proximal tubule in the pars convoluta and pars recta. Electron-microscopic immunohistochemistry showed labeling on microvilli and in apical endocytic vacuoles, dense apical tubules, and lysosomes. These results indicate that ABP is involved in proximal tubule endocytosis.

Low-affinity transport of pyroglutamyl-histidine in renal brush-border membrane vesicles

1989 ◽  
Vol 257 (5) ◽  
pp. C971-C975 ◽  
Author(s):  
H. A. Skopicki ◽  
K. Fisher ◽  
D. Zikos ◽  
G. Flouret ◽  
D. R. Peterson
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Proximal Tubular Cells ◽  
Tubular Cells ◽  
Luminal Membrane ◽  
Renal Brush Border Membrane ◽  
Proximal Tubular ◽  
Renal Brush Border

These studies were performed to determine if a low-affinity carrier is present in the luminal membrane of proximal tubular cells for the transport of the dipeptide, pyroglutamyl-histidine (pGlu-His). We have previously described the existence of a specific, high-affinity, low-capacity [transport constant (Kt) = 9.3 X 10(-8) M, Vmax = 6.1 X 10(-12) mol.mg-1.min-1] carrier for pGlu-His in renal brush-border membrane vesicles. In the present study, we sought to demonstrate that multiple carriers exist for the transport of a single dipeptide by determining whether a low-affinity carrier also exists for the uptake of pGlu-His. Transport of pGlu-His into brush-border membrane vesicles was saturable over the concentration range of 10(-5)-10(-3) M, yielding a Kt of 6.3 X 10(-5) M and a Vmax of 2.2 X 10(-10) mol.mg-1.min-1. Uptake was inhibited by the dipeptides glycyl-proline, glycyl-sarcosine, and carnosine but not by the tripeptide pyroglutamyl-histidyl-prolinamide. We conclude that 1) pGlu-His is transported across the luminal membrane of the proximal tubule by multiple carriers and 2) the lower affinity carrier, unlike the higher affinity carrier, is nonspecific with respect to other dipeptides.

Enhancement of Gentamicin-Induced Inhibition of Phosphatidylinositol Hydrolysis in Rabbit Renal Proximal Tubular Brush-Border Membrane by Furosemide

Renal Failure ◽  
1989 ◽  
Vol 11 (2-3) ◽  
pp. 105-109 ◽  
Author(s):  
Hajime Nakahama ◽  
SungHyo Shin ◽  
Toshiki Moriyama ◽  
Masahiro Kakihara ◽  
Yoshifumi Fukuhara ◽  
...  
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Proximal Tubular ◽  
Renal Proximal Tubular

Effect of acute acidemia on phosphate uptake by renal proximal tubular brush-border membranes

1986 ◽  
Vol 251 (5) ◽  
pp. F889-F896
Author(s):  
B. S. Levine ◽  
J. A. Kraut ◽  
D. R. Mishler ◽  
P. W. Crooks
Keyword(s):  
Metabolic Acidosis ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Respiratory Acidosis ◽  
Tissue Slices ◽  
Pi Transport ◽  
Proximal Tubular ◽  
Renal Proximal Tubular ◽  
Plasma Phosphorus

Prolonged metabolic acidosis is associated with depressed phosphate (Pi) uptake by the brush-border membrane (BBM) of the proximal tubule. To examine if changes in systemic pH underlie this inhibition, we measured Pi transport by renal cortical BBM from thyroparathyroidectomized rats with respiratory or metabolic acidosis of 1 or 3 h, respectively, and in appropriate controls. Also, Pi transport was measured in BBM prepared using tissue slices from nonacidotic rats that were preincubated for 20 or 45 min at either pH 6.9 (HCO3 = 10 mM, CO2 = 10%) or 7.4 (HCO3 = 10 mM, CO2 = 2.5%). Despite comparable acidemia (pH 7.06 +/- 0.05 with respiratory acidosis and 7.10 +/- 0.03 with metabolic acidosis), Na-dependent Pi uptake at 5 s incubation was reduced by 15.2 +/- 3.5% with respiratory acidosis compared with paired controls. It was not altered with metabolic acidosis. Vmax in respiratory acidosis (1.2 nmol X mg protein-1 X 5 s-1) was less than in controls (1.6); Kt was similar in both groups. 22Na transport and Na-dependent glucose transport were unchanged. Plasma phosphorus (P) increased from 8.75 +/- 0.35 mg/dl to 12.42 +/- 1.9 with respiratory acidosis. Therefore BBM vesicles transport was measured in controls after plasma P was raised. Under these conditions, Pi transport was similar to that with respiratory acidosis. Also Pi transport by BBM was unchanged when tissue slices were preincubated in vitro at high CO2 concentrations for 20 or 45 min. Thus respiratory acidosis specifically inhibits Na-dependent Pi transport by decreasing the number or rate of the BBM Pi carrier.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Homer Smith Award. Cellular mechanisms in proximal tubular Pi reabsorption: some answers and more questions.

1992 ◽  
Vol 2 (12) ◽  
pp. 1649-1665
Author(s):  
H Murer
Keyword(s):  
Protein Kinase ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Transport Rate ◽  
Transport Systems ◽  
Expression Cloning ◽  
Cellular Mechanisms ◽  
Proximal Tubular ◽  
Cotransport System ◽  
Pi Deprivation

Inorganic phosphate (Pi) is reabsorbed mainly in the proximal tubule, by a second active Na-dependent transport mechanism. Na/Pi cotransport with a stoichiometry exceeding unity mediates uphill flux across the brush border membrane; at the basolateral cell surface, two separate transport systems are involved in equilibrating Pi fluxes. The protein structure of a rabbit renal cortex Na/Pi cotransport system has been identified recently by expression cloning. The regulation of tubular Pi reabsorption involves mainly alterations in the transport rate of the brush border membrane Na/Pi cotransport system. The regulation of this transport step by either parathyroid hormone (PTH) or Pi deprivation is discussed, mostly on the basis of observations made with a tissue culture model, OK cells derived from opossum kidney. In this model, PTH may use a dual signaling cascade to inhibit apical Na/Pi cotransport (phospholipase C/protein kinase C and adenylate cyclase/protein kinase A). PTH action on Na/Pi cotransport may involve an endocytosis mechanism. For the regulation of apical Na/Pi cotransport by chronic Pi deprivation, the number of "Na/Pi cotransporter" molecules seems to be unaffected; the increased transport rate is apparently related to an "unknown" stimulating event at the membrane level (e.g., a change in the lipid microenvironment), which itself is under the control of protein synthesis/degradation. The availability of new tools (cloning of Na/Pi cotransporter(s) and of PTH receptor(s)) will allow us to enter into a new era in the study of cellular mechanisms involved in proximal tubular Pi reabsorption.

Increased Na+-H+ exchange in brush border vesicles from dogs with renal failure

1982 ◽  
Vol 243 (3) ◽  
pp. F293-F299 ◽  
Author(s):  
D. E. Cohn ◽  
K. A. Hruska ◽  
S. Klahr ◽  
M. R. Hammerman
Keyword(s):  
Renal Failure ◽  
Chronic Renal Failure ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Renal Brush Border Membrane ◽  
Proximal Tubular ◽  
Remnant Kidney ◽  
Na Uptake ◽  
Renal Brush Border

In the remnant kidney model of chronic renal failure, absolute reabsorption of Na+ in the proximal tubule of the remaining nephrons is increased over normal. Absolute proximal tubular reabsorption of bicarbonate and proximal tubular H+ excretion per nephron have also been shown to be increased over normal in his model of renal disease. Na+ uptake in membrane vesicles isolated from the brush border membrane of remnant kidneys of dogs with chronic renal failure is increased over uptake in membrane vesicles isolated from kidneys of normal dogs. In the present studies an amiloride-sensitive, electroneutral Na+-H+ exchanger was identified in canine renal brush border membrane vesicles. Na+ uptake in membrane vesicles in the presence of an initial H+ gradient (intravesicular pH less than extravesicular pH) was increased in membrane vesicles isolated from the remnant kidneys of dogs with chronic renal failure over that in membrane vesicles from kidneys of normal dogs. This increase was abolished by amiloride. It is possible that the alterations in Na+ and bicarbonate reabsorption and H+ excretion in the remnant kidney model of chronic renal failure can be explained on the basis of increased activity of the Na+-H+ exchanger in the renal brush border membrane.

Cloning of a rabbit renal Na-Pi cotransporter, which is regulated by dietary phosphate

1995 ◽  
Vol 268 (4) ◽  
pp. F626-F633 ◽  
Author(s):  
T. Verri ◽  
D. Markovich ◽  
C. Perego ◽  
F. Norbis ◽  
G. Stange ◽  
...  
Keyword(s):  
Brush Border Membrane ◽  
Regulatory Control ◽  
Kinetic Properties ◽  
Xenopus Laevis Oocytes ◽  
Type I ◽  
Type Ii ◽  
Renal Brush Border Membrane ◽  
Proximal Tubular ◽  
Dietary Phosphate ◽  
Renal Proximal Tubular

Previously, we isolated a cDNA (NaPi-1) related to a rabbit renal proximal tubular Na-Pi cotransporter (A. Werner, M.L. Moore, N. Mantei, J. Biber, G. Semenza, and H. Murer. Proc. Natl. Acad. Sci. USA 88:9608-9612, 1991.). In this study, we isolated an additional (rabbit renal) cDNA (NaPi-6), which induces Na-dependent Pi uptake in Xenopus laevis oocytes. Substrate specificity and kinetic properties corresponded to those known for rabbit renal brush-border membrane (BBM) Na-Pi cotransport. NaPi-6 was cloned by homology using NaPi-2 cDNA, a rat renal BBM Na-Pi cotransporter (S. Magagnin, A. Werner, D. Markovich, V. Sorribas, G. Stange, J. Biber, and H. Murer. Proc. Natl. Acad. Sci. USA 90: 5979-5983, 1993). NaPi-6 encodes a protein of 642 amino acids, exhibiting at least eight transmembrane domains. NaPi-6 mRNA and protein in kidneys of rabbits fed a low-Pi diet (LPD; 0.11% Pi) for 1 wk were increased by 1.5- and 4-fold, respectively, compared with those of rabbits fed a high-Pi diet (HPD; 1.20% Pi). This effect was correlated with an increase in Na-Pi cotransport of BBM vesicles isolated from animals adapted to LPD (2.5-fold with respect to HPD). In contrast, NaPi-1 mRNA and protein were not altered in response to LPD. Thus rabbit proximal tubular BBMs contain two different Na-Pi cotransport systems: NaPi-1 (type I) and NaPi-6 (type II). Only the type II transport system seems to be under regulatory control in response to low-Pi dietary intake.

Sodium-phosphate transporter adaptation to dietary phosphate deprivation in normal and hypophosphatemic mice

1995 ◽  
Vol 268 (6) ◽  
pp. G917-G924 ◽  
Author(s):  
J. F. Collins ◽  
N. Bulus ◽  
F. K. Ghishan
Keyword(s):  
Brush Border ◽  
Molecular Mechanisms ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Fold Increase ◽  
Xenopus Laevis Oocytes ◽  
Protein Levels ◽  
Renal Brush Border Membrane ◽  
Renal Tubular Reabsorption ◽  
Renal Tubular

The X-linked hypophosphatemic (Hyp) mouse is a model for hypophosphatemic vitamin D-resistant rickets and is a homologue of human X-linked hypophosphatemia. The defect in the Hyp mouse appears to be related to decreased renal tubular reabsorption of P(i) via the renal brush-border membrane (Na(+)-P(i)) transporter. Dietary P(i) deprivation upregulates Na(+)-P(i) transport activity in brush-border membrane vesicles (BBMV) isolated from both normal and Hyp mice; however, the molecular mechanisms underlying this phenomenon are not known. The current studies were designed to investigate the effect of P(i) deprivation on the renal Na(+)-P(i) transporter. Low P(i) diet upregulated Na(+)-P(i) transporter activity in isolated BBMV by 2.1-fold in normal and Hyp mice (n = 3, P = 0.01). Low P(i) diet also induced a 1.9 +/- 0.3-fold increase in normal mice and 2.9 +/- 0.4-fold increase in Hyp mice in Na(+)-P(i) transporter message levels (n = 3, P = 0.028). The increase in message level encoding the Na(+)-P(i) transporter stimulated increased Na(+)-dependent P(i) uptake by Xenopus laevis oocytes when poly(A)+ RNA was injected into them from mice on low P(i) diet (approximately 1.67-fold in normal mice and 1.33-fold in Hyp mice). Immunoreactive protein levels increased 2.3 +/- 0.4-fold in normal mice and 8.2 +/- 0.5 in the Hyp mouse kidney cortexes (n = 3, P = 0.0001) in response to dietary P(i) deprivation.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolic acidosis and parathyroidectomy increase Na+-H+ exchange in brush border vesicles

1983 ◽  
Vol 245 (2) ◽  
pp. F217-F222 ◽  
Author(s):  
D. E. Cohn ◽  
S. Klahr ◽  
M. R. Hammerman
Keyword(s):  
Metabolic Acidosis ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Chronic Metabolic Acidosis ◽  
Renal Brush Border Membrane ◽  
Dog Kidney ◽  
Renal Proximal Tubular ◽  
Renal Brush Border

Na+-H+ exchange across the brush border membrane of the renal proximal tubular cell is a mechanism for Na+ reabsorption and H+ secretion. An electroneutral Na+-H+ exchange activity has been identified in isolated renal brush border membrane vesicles from rat and dog kidney, and increased Na+-H+ exchange has been measured in brush border membrane vesicles from remnant kidneys of dogs with chronic renal failure. To ascertain whether changes in H+ secretion by the kidney observed in chronic metabolic acidosis and in states of altered parathyroid function might result from altered Na+-H+ exchange across the renal cortical cellular brush border membrane, we measured Na+-H+ exchange in brush border membrane vesicles from kidneys of dogs with chronic metabolic acidosis and from kidneys of thyroparathyroidectomized dogs. Increased amiloride-sensitive Na+-H+ exchange was demonstrated in brush border membrane vesicles from kidneys of both groups of dogs, suggesting that adaptations in H+ excretion in chronic metabolic acidosis and hypoparathyroidism might be explained by increased activity of a renal brush border membrane Na+-H+ exchanger.

Sign in / Sign up

Export Citation Format

Share Document