Sugihara Kazuhiro, Sugiyama Daijiro, Byrne James, Wolf Don P, Lowitz Kevin P, Kobayashi Yoichi, Kabir-Salmani Maryam, Nadano Daita, Aoki Daisuke, Nozawa Shiro, Nakayama Jun, Mustelin Tomas, Ruoslahti Erkki, Yamaguchi Naoto, Fukuda Michiko N
Cancer Research Center and Inflammation and Infectious Disease Center, Burnham Institute for Medical Research, 10901 North Torrey Pines Road, La Jolla, CA 92037.
Proc Natl Acad Sci U S A. 2007 Mar 6;104(10):3799-804. doi: 10.1073/pnas.0611516104. Epub 2007 Feb 26.
During human embryo implantation, trophectoderm mediates adhesion of the blastocyst to the uterine epithelium. The rapid growth of the embryo and invasion of the maternal tissue suggest adhesion-induced activation of the embryonal cells. We show here that ligation of trophinin, a homophilic cell adhesion molecule expressed on trophoblastic cells, induces tyrosine phosphorylation in trophinin-expressing trophoblastic HT-H cells. The phosphorylation could be induced in HT-H cells with the binding of trophinin-expressing cells or anti trophinin antibodies. Trophinin-dependent tyrosine phosphorylation was associated with actin reorganization. We also isolated trophinin-binding peptides from phage libraries. These peptides exhibited the consensus sequence GWRQ and seemed to reproduce the effects of trophinin-mediated cell adhesion. Upon binding of a GWRQ peptide, HT-H cells became highly proliferative and motile. HT-H cells expressed ErbB family receptors and bound EGF and heparin-binding EGF-like growth factor (HB-EGF), but ErbB family receptor phosphorylation in these cells required GWRQ. In the absence of GWRQ, trophinin interacted with the cytoplasmic protein bystin, which binds to ErbB4 and blocks its autophosphorylation. In HT-H cells, GWRQ peptide dissociated trophinin from bystin, and ErbB4 was activated. Culturing monkey blastocysts in the presence of the peptide increased total number and motility of the trophectoderm cells. These results suggest that trophinin-mediated cell adhesion functions as a molecular switch for trophectoderm activation in human embryo implantation.
在人类胚胎着床过程中，滋养外胚层介导囊胚与子宫上皮的黏附。胚胎的快速生长和母体组织的侵入表明黏附诱导了胚胎细胞的激活。我们在此表明，滋养蛋白（一种在滋养层细胞上表达的同源性细胞黏附分子）的连接可诱导表达滋养蛋白的滋养层HT-H细胞中的酪氨酸磷酸化。这种磷酸化可通过表达滋养蛋白的细胞或抗滋养蛋白抗体的结合在HT-H细胞中诱导产生。依赖滋养蛋白的酪氨酸磷酸化与肌动蛋白重组相关。我们还从噬菌体文库中分离出了滋养蛋白结合肽。这些肽呈现出一致序列GWRQ，似乎重现了滋养蛋白介导的细胞黏附的作用。在结合GWRQ肽后，HT-H细胞变得高度增殖且具有运动性。HT-H细胞表达ErbB家族受体，并结合表皮生长因子（EGF）和肝素结合表皮生长因子样生长因子（HB-EGF），但这些细胞中的ErbB家族受体磷酸化需要GWRQ。在没有GWRQ的情况下，滋养蛋白与细胞质蛋白bystin相互作用，bystin与ErbB4结合并阻断其自身磷酸化。在HT-H细胞中，GWRQ肽使滋养蛋白与bystin解离，从而激活ErbB4。在肽存在的情况下培养猴囊胚可增加滋养外胚层细胞的总数和运动性。这些结果表明，滋养蛋白介导的细胞黏附在人类胚胎着床过程中作为滋养外胚层激活的分子开关发挥作用。
