Monoclonal antibodies against the renal Na+-D-glucose cotransporter. Identification of antigenic polypeptides and demonstration of functional coupling of different Na+-cotransport systems.
Eight monoclonal antibodies are described which are directed against the renal Na+-D-glucose cotransporter. In porcine renal brush-border membranes, the antibodies either bind to one or to three polypeptides which have been identified as components of the Na+-D-glucose cotransporter (Neeb, M., Kunz, U., and Koepsell, H., (1987) J. Biol. Chem. 262, 10718-10727). Their molecular weights and isoelectric points are 75,000 and pH 5.5, 60,000 and pH 5.2, and 47,000 and pH 5.4. Six antibodies were able to influence Na+-dependent D-glucose uptake and/or Na+-dependent high affinity phlorizin binding. In the presence of Na+, the binding of all antibodies to native membrane proteins was altered by D-glucose but not by D-mannose. Since this effect was observed with D-glucose concentrations less than 1 x 10(-8) M, a high affinity D-glucose-binding site on the D-glucose transporter has been implied. Some of the antibodies probably interact also with other Na+-coupled transporters since their binding was altered by micromolar concentrations of L-lactate, L-alanine, or L-glutamate but not by the nontransported control substances D-alanine and D-glutamate. L-lactate increased the binding of one antibody in the absence but not in the presence of D-glucose. Effects of L-lactate and L-alanine on the binding of another antibody were only observed when D-glucose was present. Thus, some epitopes on the Na+-D-glucose cotransporter are altered by D-glucose and also by substrates of other Na+ cotransporters. This finding suggests functional coupling of different Na+-cotransport systems.
Koepsell
H
H
Max-Planck-Institut für Biophysik, Frankfurt am Main, West Germany.
Korn
K
K
Raszeja-Specht
A
A
Bernotat-Danielowski
S
S
Ollig
D
D
D000818:Animals; D000911:Antibodies, Monoclonal; D003840:Deoxycholic Acid / Q000494:pharmacology; D000939:Epitopes / Q000032:analysis; D005947:Glucose / Q000378:metabolism*; D007672:Kidney Cortex / Q000378:metabolism*; D007700:Kinetics; D008871:Microvilli / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000276:immunology / Q000378:metabolism*; D010695:Phlorhizin / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D013552:Swine
D000911:Antibodies, Monoclonal; D000939:Epitopes; D009004:Monosaccharide Transport Proteins; D003840:Deoxycholic Acid; D012964:Sodium; D010695:Phlorhizin; D005947:Glucose