Developmentally regulated 75-kilodalton protein expressed in LLC-PK1 cultures is a component of the renal Na+/glucose cotransport system.
Na+/D-glucose symport is a secondary active glucose transport mechanism expressed only in kidney proximal tubule and in small intestine. A monoclonal antibody that recognized the Na+/glucose symporter of pig renal brush border membranes also recognized a 75-kD protein in apical membranes isolated from highly differentiated LLC-PK1 cultures, an epithelial cell line of pig renal proximal tubule origin. The 75-kD antigen was enriched from solubilized LLC-PK1 apical membranes by means of high-pressure liquid chromatography. The symporter antigen became apparent on the apical membrane surface after the development of a confluent monolayer in correlation with the expression of transport activity. Long-term treatment of cultures with the differentiation inducer hexamethylene bisacetamide was accompanied by a dramatically increased expression of the symporter antigen as detected quantitatively by Western blot analysis and qualitatively by immunofluorescence staining. The number of symporter-positive cells was dramatically increased after inducer treatment as predicted for differentiation-regulated expression. These results identify a 75-kD protein as a component of a developmentally regulated renal Na+/glucose symporter expressed in cell culture.
Wu
J S
JS
Department of Biochemistry and Molecular Biology, University of Texas Medical School, Houston 77225.
Lever
J E
JE
D000818:Animals; D000911:Antibodies, Monoclonal; D015153:Blotting, Western; D002458:Cell Fractionation; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D004847:Epithelial Cells; D005455:Fluorescent Antibody Technique; D007668:Kidney / Q000378:metabolism*; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D013552:Swine
D000911:Antibodies, Monoclonal; D009004:Monosaccharide Transport Proteins