Characterization of the rabbit renal Na(+)-dicarboxylate cotransporter using antifusion protein antibodies

1996 ◽  
Vol 271 (6) ◽  
pp. C1808-C1816 ◽  
Author(s):  
A. M. Pajor ◽  
N. Sun
Keyword(s):  
Fusion Protein ◽  
Brush Border ◽  
Xenopus Oocytes ◽  
Polyclonal Antibodies ◽  
Membrane Vesicles ◽  
Site Directed Mutagenesis ◽  
In Vitro Translation ◽  
Western Blots ◽  
Renal Brush Border Membrane

Polyclonal antibodies were prepared against the rabbit renal Na(+)-dicarboxylate cotransporter, NaDC-1. The antibodies were raised in chickens against a fusion protein consisting of a 60-amino acid peptide from NaDC-1 and glutathione S-transferase. These antibodies specifically recognized the fusion protein in Western blots and could immunoprecipitate the full-length NaDC-1 after in vitro translation. The antifusion protein antibodies specifically recognized a protein of 63 kDa in rabbit renal brush-border membrane vesicles (BBMV), similar to the predicted mass of 66 kDa. Two proteins of 57 and 115 kDa were recognized in rabbit intestinal brush-border membranes. A protein of 66 kDa was recognized in Xenopus oocytes injected with NaDC-1 cRNA. Enzymatic deglycosylation of rabbit renal BBMV resulted in a decrease in mass by 11 kDa, consistent with N-glycosylation at a single site. Site-directed mutagenesis of the two consensus sequences for N-glycosylation in the NaDC-1 cDNA showed that Asn-576, located near the COOH-terminal, is glycosylated. The nonglycosylated mutant of NaDC-1 exhibited 50% of wild-type succinate transport activity when expressed in Xenopus oocytes, suggesting that glycosylation is not essential for function. The revised secondary structure model of NaDC-1 contains 11 putative transmembrane domains and an extracellular glycosylated COOH-terminal.

Electrogenic 2 Na/1 H antiport in crustacean epithelium is inhibited by a monoclonal antibody

1993 ◽  
Vol 264 (4) ◽  
pp. R804-R810
Author(s):  
H. Gert de Couet ◽  
L. Busquets-Turner ◽  
A. Gresham ◽  
G. A. Ahearn
Keyword(s):  
Brush Border ◽  
Membrane Vesicles ◽  
Structural Similarity ◽  
Protein Band ◽  
Monovalent Cation ◽  
Cation Binding ◽  
Western Blots ◽  
System A ◽  
Published Evidence

We have previously published evidence that suggests that Na/H exchange in crustacean and echinoderm epithelia occurs by an electrogenic antiporter protein with two external cation binding sites that accommodate Na, amiloride, or Ca and display a 2:1 monovalent cation antiport stoichiometry. The present study is an initial investigation into the molecular biology of this invertebrate electrogenic exchanger to ascertain its structural similarity to the analogous vertebrate electroneutral antiport system. A panel of monoclonal antibodies was prepared against components of lobster hepatopancreatic epithelial brush-border membranes and assayed immunohistochemically and by Western blotting. The antibodies were tested further in functional assays for their ability to interfere with electrogenic 2 Na/1 H antiport in isolated hepatopancreatic brush-border membrane vesicles. One cell line was identified producing an antibody that significantly inhibited the electrogenic exchange of cations by these membrane preparations and recognized a single protein band on Western blots of hepatopancreas, antennal gland, and gill epithelia corresponding to a molecular mass of 185 kDa. The existence of such an antibody probe may facilitate the purification of the electrogenic antiporter under denaturing conditions, in in vitro expression systems, or in prokaryotic expression libraries.

scholarly journals Involvement of disulphide bonds in the renal sodium/phosphate co-transporter NaPi-2

1997 ◽  
Vol 323 (2) ◽  
pp. 401-408 ◽  
Author(s):  
Yansen XIAO ◽  
Christian J.-C. BOYER ◽  
Éric VINCENT ◽  
André DUGRÉ ◽  
Vincent VACHON ◽  
...  
Keyword(s):  
Sodium Phosphate ◽  
Polyclonal Antibodies ◽  
Membrane Vesicles ◽  
Phosphate Transport ◽  
Reducing Agents ◽  
Western Blots ◽  
Disulphide Bonds ◽  
Reducing Conditions ◽  
Renal Brush Border Membrane ◽  
Radiation Induced

The rat renal brush border membrane sodium/phosphate co-transporter NaPi-2 was analysed in Western blots with polyclonal antibodies raised against its N-terminal and C-terminal segments. Under reducing conditions, proteins of 45–49 and 70–90 kDa (p45 and p70) were detected with N-terminal antibodies, and proteins of 40 and 70–90 kDa (p40 and p70) were detected with C-terminal antibodies. p40 and p45 apparently result from a post-translational cleavage of NaPi-2 but remain linked through one or more disulphide bonds. Glycosidase digestion showed that both polypeptides are glycosylated; the cleavage site could thus be located between Asn-298 and Asn-328, which have been shown to constitute the only two N-glycosylated residues in NaPi-2. In the absence of reducing agents, both N-terminal and C-terminal antibodies detected p70 and a protein of 180 kDa (p180), suggesting the presence of p70 dimers. Much higher concentrations of β-mercaptoethanol were required to produce a given effect in intact membrane vesicles than in solubilized proteins, indicating that the affected disulphide bonds are not exposed at the surface of the co-transporter. Phosphate transport activity decreased with increasing concentrations of reducing agents [β-mercaptoethanol, dithiothreitol and tris-(2-carboxyethyl)phosphine] and was linearly correlated with the amount of p180 detected. The target sizes estimated from the radiation-induced loss of intensity of p40, p70 and p180 were all approx. 190 kDa, suggesting that NaPi-2 exists as an oligomeric protein in which the subunits are sufficiently close to one another to allow substantial energy transfer between the monomers. When protein samples were pretreated with β-mercaptoethanol [2.5% and 5% (v/v) to optimize the detection of p40 and p70] before irradiation, target sizes estimated from the radiation-induced loss of intensity of p40 and p70 were 74 and 92 kDa respectively, showing the presence of disulphide bridges in the molecular structure of NaPi-2.

Ontogeny of DA1 receptor-mediated natriuresis in the rat: in vivo and in vitro correlations

1992 ◽  
Vol 263 (3) ◽  
pp. R631-R638 ◽  
Author(s):  
S. Kaneko ◽  
F. Albrecht ◽  
L. D. Asico ◽  
G. M. Eisner ◽  
J. E. Robillard ◽  
...  
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Receptor Subtypes ◽  
Renal Brush Border Membrane ◽  
Natriuretic Effect ◽  
Old Rats ◽  
22Na Uptake

The natriuretic and diuretic effects of dopamine are attenuated in the young. Because dopamine has actions on receptors (e.g., adrenergic, serotonin) other than dopamine, we studied a novel dopamine agonist, pramipexole, which has a selectivity to both DA1 and DA2-receptor subtypes. Intravenous administration of pramipexole resulted in a dose-related (1, 10, and 100 micrograms.kg-1.min-1) increase in urine flow and absolute and fractional sodium excretion and a decrease in mean arterial pressure (MAP) in three groups of rats studied. Pramipexole induced a greater decrease in MAP in 6- to 7- (n = 5) and 9- to 16- (n = 6) than in 3- to 4-wk-old (n = 8) rats; the natriuresis and diuresis were greatest in 12- to 16- and least in 3- to 4-wk-old rats. The renal effects of pramipexole were mainly due to actions at the DA1 receptor, since these effects were completely blocked by the coinfusion of a DA1 antagonist, SKF 83742. To explore further a cause of the attenuated natriuretic effect of pramipexole in the young, we studied the effect of a selective DA1-receptor agonist, fenoldopam, on amiloride-sensitive 22Na+ uptake in renal brush-border membrane vesicles. The 3-s amiloride-sensitive uptake was inhibited (45%) by fenoldopam (5 x 10(-5)M) in 9- to 16- (n = 6) but not in 3- to 4-wk-old (n = 5) rats. These studies suggest that the attenuated natriuretic effect of dopamine in the young is in part due to decreased DA1 action on the brush-border membrane Na(+)-H+ exchanger.

Gentamicin inhibits carrier-mediated dipeptide transport in kidney

1996 ◽  
Vol 270 (3) ◽  
pp. F531-F538
Author(s):  
H. A. Skopicki ◽  
D. Zikos ◽  
E. J. Sukowski ◽  
K. A. Fisher ◽  
D. R. Peterson
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Morphological Changes ◽  
Membrane Vesicles ◽  
Renal Brush Border Membrane ◽  
Dipeptide Transport ◽  
Vitro Effect ◽  
Renal Brush Border

The effect of gentamicin on transport of pyroglutamylhistidine (pGlu-His) was examined in rabbit renal brush-border membrane vesicles (BBMV). Gentamicin, an aminoglycoside antibiotic, is limited in its usage because of nephrotoxicity characterized in part by transport defects in the proximal tubule. Since there is no information regarding the effects of gentamicin on renal peptide carriers, uptake of [3H]pGlu-His was measured in BBMV following either in vivo or in vitro exposure to the antibiotic. One hour after in vivo administration, the maximal rate (Vmax) for pGlu-His transport was significantly reduced in isolated membrane vesicles washed free of the drug, but the apparent Michaelis constant (Km) was unaltered. Coincubation of membranes with gentamicin during measurements of pGlu-His uptake had a similar effect, causing a significant decrease in the Vmax but not the Km of transport. The addition of 5 mM magnesium to the uptake medium prevented the in vitro but not the in vivo effect. The data indicate that high doses of gentamicin inhibit the capacity but not the affinity of dipeptide transport in the kidney, prior to morphological changes which typify acute tubular necrosis. The in vitro effect is rapid and involves a direct action of gentamicin on the brush-border membrane. The in vivo experiments show that toxicity may be prolonged and remains following removal of the drug from the renal brush border.

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.

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