title: Proteoglycans in polarized epithelial Madin-Darby canine kidney cells.
abstract: Madin-Darby canine kidney (MDCK) cells were cultured on polycarbonate filters to study the synthesis and sorting of proteoglycans in polarized epithelial cells. Two strains of MDCK cells were used. MDCK I cells resemble distal tubule epithelial cells, and MDCK II cells share some characteristics with proximal tubule cells. Both strains were grown to confluency and labelled with [35S]sulphate for 24 h. The apical and basolateral media and the cell fractions were harvested and analysed by DEAE ion-exchange chromatography. A large portion of the [35S]sulphate-labelled macromolecules bound strongly to the ion-exchange columns, and could be eluted in three distinct peaks. The latest eluting peak was demonstrated to contain almost exclusively chondroitin sulphate, whereas peak 2 contained mostly heparan sulphate, demonstrated by using chondroitinase ABC and nitrous acid (pH 1.5) respectively to depolymerize the [35S]glycosaminoglycan chains. Peak 1 contained negligible amounts of proteoglycans. Large differences could be observed in proteoglycan sorting in MDCK I and II cells. Strain I secreted approx. 67% of the proteoglycans to the apical side and 17% to the basolateral side. The cell fraction contained 17% of the proteoglycans after 24 h of labelling. In contrast, 19% of the proteoglycans were sorted to the apical side of MDCK II cells and 61% to the basolateral side, whereas the cell fraction contained 20%. Furthermore, the level of [35S]proteoglycan biosynthesis (apical and basolateral media and cell fraction total) was higher in MDCK I cells than in strain II. Based on the amount of material degraded by chondroitinase ABC and nitrous acid respectively, and the total amounts of [35S]proteoglycans recovered from the cells, it was calculated that the MDCK I strain synthesized approx. 56% chondroitin sulphate and 44% heparan sulphate. In contrast, the MDCK II strain synthesized 69% heparan sulphate and 31% chondroitin sulphate. To further identify the [35S]proteoglycans synthesized by MDCK I and II cells, antibodies against perlecan, versican and syndecan were used. The antibody against mouse syndecan did not cross-react with any of the proteoglycans produced in MDCK I or II cells. Both MDCK I and II cells expressed perlecan; 57-61% could be recovered from the basolateral fractions and 18-34% from the apical medium. Versican was also found in both MDCK I and II cells. Compared with perlecan, a larger percentage of versican (43-53%) was found in the cell fractions.
mesh_terms: D000818:Animals; D002460:Cell Line; D016764:Cell Polarity; D011508:Chondroitin Sulfate Proteoglycans / Q000032:analysis / Q000096:biosynthesis* / Q000276:immunology; D002852:Chromatography, Ion Exchange; D004285:Dogs; D004591:Electrophoresis, Polyacrylamide Gel; D004983:Ethanolamines; D019812:Heparan Sulfate Proteoglycans; D006497:Heparan Sulfate / Q000032:analysis / Q000096:biosynthesis* / Q000276:immunology; D007686:Kidney Tubules, Distal / Q000166:cytology* / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000166:cytology* / Q000378:metabolism; D046911:Macromolecular Substances; D051379:Mice; D011509:Proteoglycans / Q000032:analysis / Q000096:biosynthesis* / Q000276:immunology; D012967:Sodium Dodecyl Sulfate; D013462:Sulfur Radioisotopes
chemical_list: D011508:Chondroitin Sulfate Proteoglycans; D004983:Ethanolamines; D019812:Heparan Sulfate Proteoglycans; D006497:Heparan Sulfate; D046911:Macromolecular Substances; D011509:Proteoglycans; D012967:Sodium Dodecyl Sulfate; D013462:Sulfur Radioisotopes; C007369:2-diethylaminoethanol