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

Development. 1999 May;126(9):1997-2005. doi: 10.1242/dev.126.9.1997.

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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • ADP Ribose Transferases*
  • Animals
  • Bacterial Toxins*
  • Blastocyst / physiology*
  • Cell Survival / drug effects
  • Embryo Implantation / physiology*
  • Epidermal Growth Factor / physiology*
  • Epithelium / embryology
  • ErbB Receptors / deficiency
  • ErbB Receptors / genetics
  • ErbB Receptors / physiology*
  • Exotoxins / toxicity
  • Female
  • Genes, erbB-1*
  • Heparan Sulfate Proteoglycans / metabolism
  • Heparin-binding EGF-like Growth Factor
  • Humans
  • Intercellular Signaling Peptides and Proteins
  • Leucine / metabolism
  • Male
  • Mice
  • Mice, Knockout
  • Pregnancy
  • Pseudomonas
  • Receptor, ErbB-4
  • Reverse Transcriptase Polymerase Chain Reaction
  • Tumor Cells, Cultured
  • Virulence Factors*

Substances

  • Bacterial Toxins
  • Exotoxins
  • HBEGF protein, human
  • Hbegf protein, mouse
  • Heparan Sulfate Proteoglycans
  • Heparin-binding EGF-like Growth Factor
  • Intercellular Signaling Peptides and Proteins
  • Virulence Factors
  • Epidermal Growth Factor
  • ADP Ribose Transferases
  • Pseudomonas aeruginosa exotoxin A
  • ERBB4 protein, human
  • ErbB Receptors
  • Erbb4 protein, mouse
  • Receptor, ErbB-4
  • Leucine