title: Differential expression of GalNAc-4-sulfotransferase and GalNAc-transferase results in distinct glycoforms of carbonic anhydrase VI in parotid and submaxillary glands.
abstract: Differential expression of glycosyltransferases has the potential to generate functionally distinct glycoforms of otherwise identical proteins. We have previously demonstrated the presence of unique oligosaccharides terminating with GalNAc-4-SO4 on the pituitary glycoproteins lutropin (LH), thyroid stimulating hormone (TSH), and pro-opiomelanocortin (POMC). A glycoprotein hormone:GalNAc-transferase and a GalNAc-4-sulfotransferase are present in the pituitary and can account for the synthesis of these unique oligosaccharides on specific glycoproteins. Both transferases are coordinately expressed in a number of tissues in addition to pituitary, including submaxillary gland, lacrimal gland, and kidney, suggesting that additional glycoproteins bearing oligosaccharides terminating with GalNAc-4-SO4 are synthesized in these tissues. In this study we show that while the glycoprotein hormone:GalNAc-transferase and the GalNAc-4-sulfotransferase are coordinately expressed in bovine submaxillary gland, the GalNAc-transferase is expressed in the parotid gland in the absence of the GalNAc-4-sulfotransferase. The relative expression of these two transferases in submaxillary and parotid glands correlates with the presence of unique Asn-linked oligosaccharides on carbonic anhydrase VI (CA VI) synthesized in each of these tissues. The majority of Asn-linked oligosaccharides on CA VI synthesized in submaxillary gland terminate with GalNAc-4-SO4. In contrast, CA VI which is synthesized in bovine parotid gland bears oligosaccharides which terminate predominantly with beta 1,4-linked GalNAc which is not sulfated. The presence of different terminal residues on the Asn-linked oligosaccharides of submaxillary and parotid CA VI thus correlates with the complement of transferases in these glands and suggests differing biological roles for submaxillary and parotid CA VI.
authors.affiliation: Department of Pathology, Washington University School of Medicine, St. Louis, Missouri 63110.
authors.forename: L V
authors.initials: LV
authors.lastname: Hooper
authors.forename: M C
authors.initials: MC
authors.lastname: Beranek
authors.forename: S M
authors.initials: SM
authors.lastname: Manzella
authors.forename: J U
authors.initials: JU
authors.lastname: Baenziger
mesh_terms: D000818:Animals; D001216:Asparagine; D002240:Carbohydrate Sequence; D002256:Carbonic Anhydrases / Q000096:biosynthesis* / Q000302:isolation & purification; D002417:Cattle; D002846:Chromatography, Affinity; D002851:Chromatography, High Pressure Liquid; D015971:Gene Expression Regulation, Enzymologic; D006023:Glycoproteins / Q000096:biosynthesis*; D007527:Isoenzymes / Q000096:biosynthesis* / Q000302:isolation & purification; D008969:Molecular Sequence Data; D017350:N-Acetylgalactosaminyltransferases / Q000096:biosynthesis*; D009844:Oligosaccharides / Q000737:chemistry / Q000302:isolation & purification; D010306:Parotid Gland / Q000201:enzymology*; D013363:Submandibular Gland / Q000201:enzymology*; D015238:Sulfotransferases / Q000096:biosynthesis*; D013961:Thyroid Gland / Q000201:enzymology
chemical_list: D006023:Glycoproteins; D007527:Isoenzymes; D009844:Oligosaccharides; D001216:Asparagine; D017350:N-Acetylgalactosaminyltransferases; C072136:glycoprotein hormone-specific N-acetylgalactosamine transferase; C092527:N-acetylgalactosamine-4-sulfotransferase; D015238:Sulfotransferases; D002256:Carbonic Anhydrases