title: Heparin-binding EGF-like growth factor interacts with mouse blastocysts independently of ErbB1: a possible role for heparan sulfate proteoglycans and ErbB4 in blastocyst implantation.
abstract: Blastocyst implantation requires molecular and cellular interactions between the uterine luminal epithelium and blastocyst trophectoderm. We have previously shown that heparin-binding EGF-like growth factor (HB-EGF) is induced in the mouse luminal epithelium solely at the site of blastocyst apposition at 16:00 hours on day 4 of pregnancy prior to the attachment reaction (22:00-23:00 hours), and that HB-EGF promotes blastocyst growth, zona-hatching and trophoblast outgrowth. To delineate which EGF receptors participate in blastocyst activation, the toxicity of chimeric toxins composed of HB-EGF or TGF-(&agr;) coupled to Pseudomonas exotoxin (PE) were used as measures of receptor expression. TGF-(&agr;) or HB-EGF binds to EGF-receptor (ErbB1), while HB-EGF, in addition, binds to ErbB4. The results indicate that ErbB1 is inefficient in mediating TGF-(&agr;)-PE or HB-EGF-PE toxicity as follows: (i) TGF-(&agr;)-PE was relatively inferior in killing blastocysts, 100-fold less than HB-EGF-PE, (ii) analysis of blastocysts isolated from cross-bred egfr+/- mice demonstrated that HB-EGF-PE, but not TGF-(&agr;)-PE, killed egfr-/- blastocysts, and (iii) blastocysts that survived TGF-(&agr;)-PE were nevertheless killed by HB-EGF-PE. HB-EGF-PE toxicity was partially mediated by cell surface heparan sulfate proteoglycans (HSPG), since a peptide corresponding to the heparin-binding domain of HB-EGF as well as heparitinase treatment protected the blastocysts from the toxic effects of HB-EGF-PE by about 40%. ErbB4 is a candidate for being an HB-EGF-responsive receptor since RT-PCR analysis demonstrated that day 4 mouse blastocysts express two different erbB4 isoforms and immunostaining with anti-ErbB4 antibodies confirmed that ErbB4 protein is expressed at the apical surface of the trophectoderm cells. It is concluded that (i) HB-EGF interacts with the blastocyst cell surface via high-affinity receptors other than ErbB1, (ii) the HB-EGF interaction with high-affinity blastocysts receptors is regulated by heparan sulfate, and (iii) ErbB4 is a candidate for being a high-affinity receptor for HB-EGF on the surface of implantation-competent blastocysts.
authors: Department of Molecular and Integrative Physiology, Ralph L. Smith Research Center, University of Kansas Medical Center, Kansas City, KS 66160-7338, USA.
authors: B C
authors: BC
authors: Paria
authors: K
authors: K
authors: Elenius
authors: M
authors: M
authors: Klagsbrun
authors: S K
authors: SK
authors: Dey
mesh_terms: D036002:ADP Ribose Transferases; D000818:Animals; D001427:Bacterial Toxins; D001755:Blastocyst / Q000502:physiology*; D002470:Cell Survival / Q000187:drug effects; D010064:Embryo Implantation / Q000502:physiology*; D004815:Epidermal Growth Factor / Q000502:physiology*; D004848:Epithelium / Q000196:embryology; D066246:ErbB Receptors / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D005098:Exotoxins / Q000633:toxicity; D005260:Female; D018773:Genes, erbB-1; D019812:Heparan Sulfate Proteoglycans / Q000378:metabolism; D066257:Heparin-binding EGF-like Growth Factor; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D007930:Leucine / Q000378:metabolism; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D011247:Pregnancy; D011549:Pseudomonas; D066247:Receptor, ErbB-4; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A
chemical_list: D036002:ADP Ribose Transferases; D001427:Bacterial Toxins; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D005098:Exotoxins; D019812:Heparan Sulfate Proteoglycans; D066257:Heparin-binding EGF-like Growth Factor; D036341:Intercellular Signaling Peptides and Proteins; D007930:Leucine; D066247:Receptor, ErbB-4; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A; C587883:HBEGF protein, human; C587884:Hbegf protein, mouse; C587689:ERBB4 protein, human; C587690:Erbb4 protein, mouse