Conley Barbara A, Koleva Rositsa, Smith Joshua D, Kacer Doreen, Zhang Dongwang, Bernabéu Carmelo, Vary Calvin P H
Center for Molecular Medicine, Maine Medical Center Research Institute, Scarborough, Maine 04074, USA.
J Biol Chem. 2004 Jun 25;279(26):27440-9. doi: 10.1074/jbc.M312561200. Epub 2004 Apr 14.
Mutations in the human endoglin gene result in hereditary hemorrhagic telangiectasia type 1, a vascular disorder characterized by multisystemic vascular dysplasia, arteriovenous malformations, and focal dilatation of postcapillary venules. Previous studies have implicated endoglin in the inhibition of cell migration in vivo and in vitro. In the course of studies to address the relationship of the conserved cytosolic domain to endoglin function, we identified zyxin, a LIM domain protein that is concentrated at focal adhesions, as an interactor with endoglin in human umbilical vein vascular endothelial cells. This interaction is localized within the 47-amino acid carboxyl-terminal cytosolic domain of endoglin, and maps within zyxin residues 326-572. The endoglin-zyxin interaction was found to be largely mediated by the third LIM domain of zyxin, and is specific for endoglin because the homologous cytosolic domain of the transforming growth factor-beta type III receptor, betaglycan, fails to interact with zyxin. Expression of endoglin is associated with reduction of zyxin, as well as its interacting proteins p130(cas) and CrkII, from a focal adhesion protein fraction, and this reduction is correlated with inhibition of cell migration. We also show that endoglin-dependent: (i) inhibition of cell migration, (ii) reduction of focal adhesion-associated p130(cas)/CrkII protein levels, (iii) tyrosine phosphorylation of p130(cas), and (iv) focal adhesion-associated endoglin levels are mediated by the cytosolic domain of endoglin. These results suggest a novel mechanism of endoglin function involving its interaction with LIM domain-containing proteins, and associated adapter proteins, affecting sites of focal adhesion.
人类内皮糖蛋白基因的突变会导致遗传性出血性毛细血管扩张症1型，这是一种血管疾病，其特征为多系统血管发育异常、动静脉畸形以及毛细血管后微静脉的局灶性扩张。先前的研究表明内皮糖蛋白在体内和体外均具有抑制细胞迁移的作用。在研究保守的胞质结构域与内皮糖蛋白功能之间关系的过程中，我们在人脐静脉血管内皮细胞中鉴定出一种名为斑联蛋白的LIM结构域蛋白，它集中于粘着斑，是与内皮糖蛋白相互作用的蛋白。这种相互作用定位于内皮糖蛋白47个氨基酸的羧基末端胞质结构域内，且定位于斑联蛋白326 - 572位残基内。发现内皮糖蛋白与斑联蛋白的相互作用主要由斑联蛋白的第三个LIM结构域介导，并且对内皮糖蛋白具有特异性，因为转化生长因子βⅢ型受体（β聚糖）的同源胞质结构域不能与斑联蛋白相互作用。内皮糖蛋白的表达与粘着斑蛋白组分中斑联蛋白及其相互作用蛋白p130（cas）和CrkII的减少相关，并且这种减少与细胞迁移的抑制相关。我们还表明，内皮糖蛋白依赖性：（i）细胞迁移的抑制，（ii）粘着斑相关的p130（cas）/CrkII蛋白水平的降低，（iii）p130（cas）的酪氨酸磷酸化，以及（iv）粘着斑相关的内皮糖蛋白水平由内皮糖蛋白的胞质结构域介导。这些结果提示了一种新的内皮糖蛋白功能机制，涉及它与含LIM结构域的蛋白以及相关衔接蛋白的相互作用，影响粘着斑位点。
