title: A tetraantennary glycan with bisecting N-acetylglucosamine and the Sd(a) antigen is the predominant N-glycan on bovine pregnancy-associated glycoproteins.
abstract: Pregnancy-associated glycoproteins (PAGs) are major secretory proteins of trophoblast cells in ruminants. Binucleate trophoblast giant cells (BNCs) store these proteins in secretory granules and release them into the maternal organism after fusion with maternal uterine epithelial cells. By matrix assisted laser desorption ionisation-mass spectrometry (MALDI-MS) analysis and linkage analysis, we show that by far, the most abundant N-glycan of PAGs in midpregnancy is a tetraantennary core-fucosylated structure with a bisecting N-acetylglucosamine (GlcNAc). All four antennae consist of the Sd(a)-antigen (NeuAcalpha2-3[GalNAcbeta1-4]Galbeta1-4GlcNAc-). Immunohistochemistry with the mono- clonal antibody CT1, which recognizes the Sd(a)-antigen, shows that BNC granules contain the Sd(a)-antigen from gestation day (gd) 32 until a few days before parturition. Lectin histochemistry with Maackia amurensis lectin (MAL), which binds to alpha2-3sialylated lactosamine, shows that BNC granules are MAL-positive prior to gd 32 and also at parturition. The observed tetraantennary glycan is a highly unusual structure, since during the synthesis of N-glycans, the insertion of a bisecting GlcNAc inhibits the activity of the GlcNAc-transferases that leads to tri- and tetraantennary glycans. The study defines the substantial changes of PAG N-glycosylation in the course of pregnancy. This promotes the hypothesis that PAGs may have different carbohydrate-mediated functions at different stages of pregnancy.
authors.affiliation: Abteilung Neuroanatomie, Medizinische Hochschule Hannover, 30625 Hannover, Germany. karl.klisch@nottingham.ac.uk
authors.forename: Karl
authors.initials: K
authors.lastname: Klisch
authors.forename: Evelyne
authors.initials: E
authors.lastname: Jeanrond
authors.forename: Poh-Choo
authors.initials: PC
authors.lastname: Pang
authors.forename: Andreas
authors.initials: A
authors.lastname: Pich
authors.forename: Gerhard
authors.initials: G
authors.lastname: Schuler
authors.forename: Vibeke
authors.initials: V
authors.lastname: Dantzer
authors.forename: Mariusz P
authors.initials: MP
authors.lastname: Kowalewski
authors.forename: Anne
authors.initials: A
authors.lastname: Dell
mesh_terms: D000117:Acetylglucosamine / Q000032:analysis* / Q000737:chemistry; D000818:Animals; D002417:Cattle; D005260:Female; D006023:Glycoproteins / Q000737:chemistry*; D007150:Immunohistochemistry; D009844:Oligosaccharides / Q000032:analysis*; D011134:Polysaccharides / Q000737:chemistry*; D011247:Pregnancy; D011257:Pregnancy Proteins / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D006023:Glycoproteins; D009844:Oligosaccharides; D011134:Polysaccharides; D011257:Pregnancy Proteins; C106678:Sd(a) determinant; D000117:Acetylglucosamine