TYROSINE PHOSPHATASES IN ENDOTHELIAL GROWTH CONTROL

对调节新生血管和新生血管生长的内在分子控制的定义有望为实体瘤、糖尿病视网膜病变、关节炎、皮肤和其他疾病的治疗提供靶点。发育组装、重塑和维持微血管完整性是由内皮细胞对局部环境信号的反应调节的动态过程，通过表面受体传递。成熟血管内皮细胞的基本特性之一是依赖于细胞环境的过度增殖限制。我们提出的假设是，内皮细胞受体酪氨酸磷酸酶ECRTP/CD148通过与对抗性受体的旁分泌接触传递细胞生长停滞信号。特异性结合ECRTP/CD148胞外结构域序列的单抗ECRTP.ab1将其表达定位于肾脏动脉和毛细血管内皮细胞以及其他组织。内皮祖细胞在进入肾小球毛细血管之前表达ECRTP/CD148，ECRTP/CD148聚集在内皮间接触点。二价形式的ECRTP.ab1阻止培养的内皮细胞的增殖和迁移，在小鼠角膜实验中抑制血管生成，并促进细胞内酪氨酸磷酸蛋白的去磷酸化。ECRTP/CD148在缺陷细胞系中的表达给予抗体诱导的生长抑制，这种抑制依赖于内在的酪氨酸磷酸酶活性。目前的方案描述了以下计划：1)定义CD148的功能性反式受体，2)鉴定ECRTP/CD148的细胞内底物及其在内皮细胞生长停止中的作用，3)确定ECRTP/CD148在血管发育中的功能。同源重组ES系和小鼠将确定ECRTP/CD148在发育血管组装中的功能。这些研究将扩展调控血管生成的分子控制的定义，并将为抗血管生成治疗定义新的分子靶点。

Definition of the intrinsic molecular controls that regulate angiogenic and vasculogenic blood vessel growth promises to provide targets for therapy of solid tumors, diabetic retinopathy, arthritis, skin and other diseases. Developmental assembly, remodeling and maintenance of microvascular integrity are dynamic processes regulated by endothelial responses to local environmental cues, transduced through surface receptors. One of the properties fundamental to endothelium in mature vessels is cell context dependent constraints over proliferation. We have advanced the hypothesis that an endothelial receptor tyrosine phosphatase, ECRTP/CD148, transduces cell growth arrest signals on juxtacrine contact with a counter-receptor. A monoclonal antibody, ECRTP.ab1, that specifically binds ECRTP/CD148 ectodomain sequences localizes its expression to endothelium of arteries and capillaries in kidney, and other tissues. Endothelial progenitor cells express ECRTP/CD148 prior to their incorporation into developing glomerular capillaries of kidney, and ECRTP/CD148 accumulates at inter-endothelial points of contact. Bivalent forms of ECRTP.ab1 block cultured endothelial cell proliferation and migration, inhibit angiogenesis in a mouse corneal assay, and promote dephosphorylation of intracellular tyrosine phosphoproteins. Expression of ECRTP/CD148 in deficient cell lines confers antibody-induced growth inhibition that is dependent upon intrinsic tyrosine phosphatase activity. The current proposal describes plans to: 1) define a functional counter-receptor to CD148, 2) to identify intracellular substrates of ECRTP/CD148 and their role in endothelial growth arrest, and 3) to define ECRTP/CD148 function during vascular development. Homologous recombinant ES lines and mice will define function of ECRTP/CD148 in developmental vascular assembly. These studies will extend definition of molecular controls regulating angiogenesis, and will define new molecular targets for anti-angiogenic therapies.