Pregnancy Specific Glycoprotein 17 Binds to the Extracellular Loop 2 of Its Receptor, CD9, and Induces the Secretion of IL-10, IL-6, PGE2, and TGFBeta1 in Murine Macrophages
Abstract
Pregnancy specific glycoproteins (PSGs) are a family of proteins produced by primate and rodent placentas and secreted into the maternal circulation. In humans PSGs are detected in maternal serum from the time of implantation, and their concentration increases when pregnancy progresses, reaching 200-400 microgram/ml at term. The correlation between low levels of PSGs and poor pregnancy outcomes suggests PSGs play a role in the regulation of maternal immunity to the semi-allogeneic fetus. We have previously reported that human and murine PSGs induce antiinflammatory cytokines in monocytes, and identified CD9 as the cellular receptor for murine PSG17. However, the role of CD9 in cytokine induction mediated by PSG17 as well as the signaling mechanism triggered in macrophages in response to PSG17 remain largely unknown. The present research attempted to shed light on these two areas. Protein-protein interaction assays were employed to examine the direct interaction between the two molecules, showing that the N1 domain of PSG17 (PSG17N) bound directly to the second extracellular loop of CD9 (CD9-EC2). FACS and ELISA revealed that phenylalanine 174 in CD9-EC2 was essential for PSG17 binding. Treatment of C57BL/6 macrophages with PSG17N induced IL-10, IL-6, PGE2, and TGF(Beta sub 1) in wild type but not in CD9-deficient cells. These findings suggest that CD9 is the only biological receptor for PSG17N in the induction of these cytokines. In addition to PSG17, PSG19 was found to use CD9 as its receptor. Treatment of macrophages with PSG17N in the presence of a COX-2 specific inhibitor significantly reduced the level of IL-10 and IL-6 secretion. Furthermore, co-treatment with PSG17 and a cAMP-dependent protein kinase A inhibitor significantly decreased the production of IL-10 and IL-6. These two findings implicate the involvement of the COX-2 mediated PGE2 pathway in cytokine induction.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2004
- Accession Number
- ADA435426
Entities
People
- Cam Thi Ha
Organizations
- Uniformed Services University of the Health Sciences