Human PSG1(Pregnancy-specific beta-1-glycoprotein 1) ELISA Kit

Pregnancy-specific beta 1 glycoprotein (PSG1) is secreted from trophoblast cells of the human placenta in increasing concentrations as pregnancy progresses, becoming one of the most abundant proteins in maternal serum in the third trimester. PSG1 has seven potential N-linked glycosylation sites across its four domains. We carried out glycomic and glycoproteomic studies to characterize the glycan composition of PSG1 purified from serum of pregnant women and identified the presence of complex N-glycans containing poly LacNAc epitopes with alpha 2,3 sialyation at four sites. Using different techniques, we explored whether PSG1 can bind to galectin-1 (Gal-1) as these two proteins were previously shown to participate in processes required for a successful pregnancy. We confirmed that PSG1 binds to Gal-1 in a carbohydrate-dependent manner with an affinity of the interaction of 0.13 mu M. In addition, we determined that out of the three N-glycosylation-carrying domains, only the N and A2 domains of recombinant PSG1 interact with Gal-1. Lastly, we observed that the interaction between PSG1 and Gal-1 protects this lectin from oxidative inactivation and that PSG1 competes the ability of Gal-1 to bind to some but not all of its glycoprotein ligands.

Pregnancy specific glycoproteins (PSG) in humans constitute a family of 11 closely related glycoproteins (PSG1-8, PSG11-13) of unknown function(s), which are produced in large amounts by the placenta. As a step toward understanding the biology of PSG, specific monoclonal antibodies (mAbs) against PSG were developed and used to investigate the ultrastructural localization of PSG in the early and term placenta and in first trimester decidua. One mAb, BAP-3, was found to react with all six individually expressed PSGs representing five alternatively spliced forms, but not with any of the seven expressed members of the carcinoembryonic antigen (CEA) subfamily. The BAP-3 epitope is located in the PSG B2 domain. Using the BAP-3 mAb, PSGs were found to be expressed exclusively by the syncytiotrophoblast of first trimester and term villi. The intensity of the staining was much higher in early than in term placenta. All three main cellular compartments involved in the biosynthesis pathway of secreted proteins, i.e. rough endoplasmic reticulum, the Golgi complex and secretory vesicles, were stained for PSG. A second PSG-reactive mAb, BAP-1, also stained the apical plasma membrane of some glandular epithelial cells in first trimester decidua in addition to syncytiotrophoblast. This staining was most likely due to cross-reactivity with biliary glycoprotein (BGP). (C) 1997 W. B. Saunders Company Ltd.