Acceleration of trophoblast differentiation by heparin-binding EGF-like growth factor is dependent on the stage-specific activation of calcium influx by ErbB receptors in developing mouse blastocysts.
Heparin-binding EGF-like growth factor (HB-EGF) is expressed in the mouse endometrial epithelium during implantation exclusively at sites apposed to embryos and accelerates the development of cultured blastocysts, suggesting that it may regulate peri-implantation development in utero. We have examined the influence of HB-EGF on mouse trophoblast differentiation in vitro and the associated intracellular signaling pathways. HB-EGF both induced intracellular Ca2+ signaling and accelerated trophoblast development to an adhesion-competent stage, but only late on gestation day 4 after ErbB4, a receptor for HB-EGF, translocated from the cytoplasm to the apical surface of trophoblast cells. The acceleration of blastocyst differentiation by HB-EGF was attenuated after inhibition of protein tyrosine kinase activity or removal of surface heparan sulfate, as expected. Chelation of intracellular Ca2+ blocked the ability of HB-EGF to accelerate development, as did inhibitors of protein kinase C or calmodulin. The absence of any effect by a phospholipase C inhibitor and the requirement for extracellular Ca2+ suggested that the accrued free cytoplasmic Ca2+ did not originate from inositol phosphate-sensitive intracellular stores, but through Ca2+ influx. Indeed, N-type Ca2+ channel blockers specifically inhibited the ability of HB-EGF to both induce Ca2+ signaling and accelerate trophoblast development. We conclude that HB-EGF accelerates the differentiation of trophoblast cells to an adhesion-competent stage by inducing Ca2+ influx, which activates calmodulin and protein kinase C. An upstream role for ErbB4 in this pathway is implicated by the timing of its translocation to the trophoblast surface.
Wang
J
J
C.S. Mott Center for Human Growth and Development, Department of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.
Mayernik
L
L
Schultz
J F
JF
Armant
D R
DR
D000818:Animals; D001692:Biological Transport; D001755:Blastocyst / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism; D020013:Calcium Signaling; D002454:Cell Differentiation; D004815:Epidermal Growth Factor / Q000235:genetics / Q000378:metabolism*; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism*; D005260:Female; D006493:Heparin / Q000378:metabolism*; D066257:Heparin-binding EGF-like Growth Factor; D006497:Heparan Sulfate / Q000378:metabolism; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D066247:Receptor, ErbB-4; D014327:Trophoblasts / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*
D002118:Calcium; D015220:Calcium Channels; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D006493:Heparin; D066257:Heparin-binding EGF-like Growth Factor; D006497:Heparan Sulfate; D036341:Intercellular Signaling Peptides and Proteins; D011493:Protein Kinase C; D066247:Receptor, ErbB-4; C587883:HBEGF protein, human; C587884:Hbegf protein, mouse; C587689:ERBB4 protein, human; C587690:Erbb4 protein, mouse