title: Trophoblast adhesion of the peri-implantation mouse blastocyst is regulated by integrin signaling that targets phospholipase C.
abstract: Integrin signaling modulates trophoblast adhesion to extracellular matrices during blastocyst implantation. Fibronectin (FN)-binding activity on the apical surface of trophoblast cells is strengthened after elevation of intracellular Ca(2+) downstream of integrin ligation by FN. We report here that phosphoinositide-specific phospholipase C (PLC) mediates Ca(2+) signaling in response to FN. Pharmacological agents used to antagonize PLC (U73122) or the inositol phosphate receptor (Xestospongin C) inhibited FN-induced elevation of intracellular Ca(2+) and prevented the upregulation of FN-binding activity. In contrast, inhibitors of Ca(2+) influx through either voltage-gated or non-voltage-gated Ca(2+) channels were without effect. Inhibition of protein tyrosine kinase activity by genistein, but not G-protein inhibition by suramin, blocked FN-induced intracellular Ca(2+) signaling and upregulation of adhesion, consistent with involvement of PLC-gamma. Confocal immunofluorescence imaging of peri-implantation blastocysts demonstrated that PLC-gamma2, but not PLC-gamma1 nor PLC-beta1, accumulated near the outer surface of the embryo. Phosphotyrosine site-directed antibodies revealed phosphorylation of PLC-gamma2, but not PLC-gamma1, upon integrin ligation by FN. These data suggest that integrin-mediated activation of PLC-gamma to initiate phosphoinositide signaling and intracellular Ca(2+) mobilization is required for blastocyst adhesion to FN. Signaling cascades regulating PLC-gamma could, therefore, control a critical feature of trophoblast differentiation during peri-implantation development.
authors.affiliation: CS Mott Center for Human Growth and Development, Department of Anatomy, Wayne State University School of Medicine, Detroit, MI 48201, USA.
authors.forename: Jun
authors.initials: J
authors.lastname: Wang
authors.forename: Linda
authors.initials: L
authors.lastname: Mayernik
authors.forename: D Randall
authors.initials: DR
authors.lastname: Armant
mesh_terms: D000818:Animals; D001755:Blastocyst / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D002448:Cell Adhesion; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D003593:Cytoplasm / Q000737:chemistry; D010064:Embryo Implantation; D005260:Female; D005353:Fibronectins / Q000378:metabolism; D006801:Humans; D007295:Inositol Phosphates / Q000378:metabolism; D016023:Integrins / Q000378:metabolism*; D007527:Isoenzymes / Q000378:metabolism; D008297:Male; D051379:Mice; D051966:Phospholipase C gamma / Q000378:metabolism*; D010766:Phosphorylation; D015398:Signal Transduction; D013234:Stem Cells; D014327:Trophoblasts / Q000166:cytology / Q000502:physiology*; D015854:Up-Regulation
chemical_list: D005353:Fibronectins; D007295:Inositol Phosphates; D016023:Integrins; D007527:Isoenzymes; C058097:inositol 1,3,4-trisphosphate; D051966:Phospholipase C gamma; D002118:Calcium