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The glycosylation of pregnancy-associated glycoproteins and prolactin-related protein-I in bovine binucleate trophoblast giant cells changes before parturition

Department of Neuroanatomy, Medical School Hannover, 30625 Hannover, Germany, ¹ Vetsuisse-Faculty, Institute of Veterinary Anatomy, University of Zurich, CH-8057 Zurich, Switzerland, ² Institute of Animal Husbandry and Genetics, University of Goettingen, 37075 Goettingen, Germany, ³ Clinic for Cattle, Hannover Veterinary School, 30173 Hannover, Germany, ⁴ Laboratory of Animal Endocrinology and Reproduction, Faculty of Veterinary Medicine, University of Liége, 4000 Liége, Belgium, ⁵ Institute of Veterinary Anatomy, Justus Liebig University Giessen, 35392 Giessen, Germany and ⁶ Clinic of Veterinary Obstetrics, Gynaecology and Andrology, Justus Liebig University Giessen, 35392 Giessen, Germany

Correspondence should be addressed to K Klisch; Email: klisch.karl{at}mh-hanover.de

Binucleate trophoblast giant cells (BNC) in the bovine placenta produce glycoproteins, which are delivered into the mother after fusion of BNC with uterine epithelial cells. During most time of pregnancy, BNC produce pregnancy-associated glycoproteins (PAGs) and prolactin-related protein-I (PRP-I) with asparagine-linked lactosamine-type glycans terminating with N-acetyl-galactosamine. We show by lectin histochemistry that terminal N-acetyl-galactosamine (detected by Dolichos biflorus agglutinin, DBA) in placentomal BNC is greatly reduced prior to parturition, while lactosamine-type N-glycans (detected by Phaseolus vulgaris leucoagglutinin, PHA-L) remain unaltered. The change in DBA-staining showed no statistically significant differences between placentomes of cows with and without retention of fetal membranes. Western blots revealed that, at parturition the apparent molecular mass of PAGs and PRP-I is 1–2 kDa lower than in late pregnancy. These changes are due to alterations of asparagine-linked glycans, since the molecular weight of the peptide backbones after enzymatical release of asparagine-linked glycans is identical at late pregnancy and parturition. Lectin western blots showed a reduction of terminal N-acetyl-galactosamine on PAGs at parturition. A lectin sandwich-ELISAwas used to differentiate DBA- and PHA-L-binding PAGs in sera of pregnant and non-pregnant cows. The values for DBA-binding PAGs at parturition were not significantly different from non-pregnancy, while the values for PHA-L-binding PAGs were significantly higher at parturition. The peripartal changes of PAG- and PRP-I-glycosylation could alter functional properties of these proteins and might therefore be considered for functional studies. The differentiation of PAG glycoforms in maternal serum could be valuable for a further optimization of PAG-based pregnancy diagnosis in cattle.

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				K. Klisch, E. Jeanrond, P.-C. Pang, A. Pich, G. Schuler, V. Dantzer, M. P Kowalewski, and A. Dell A Tetraantennary Glycan with Bisecting N-Acetylglucosamine and the Sda Antigen is the Predominant N-Glycan on Bovine Pregnancy-Associated Glycoproteins Glycobiology, January 1, 2008; 18(1): 42 - 52. [Abstract] [Full Text] [PDF]