Kontos C D, Stauffer T P, Yang W P, York J D, Huang L, Blanar M A, Meyer T, Peters K G
Departments of Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA.
Mol Cell Biol. 1998 Jul;18(7):4131-40. doi: 10.1128/MCB.18.7.4131.
Tie2 is an endothelium-specific receptor tyrosine kinase that is required for both normal embryonic vascular development and tumor angiogenesis and is thought to play a role in vascular maintenance. However, the signaling pathways responsible for the function of Tie2 remain unknown. In this report, we demonstrate that the p85 subunit of phosphatidylinositol 3-kinase (PI3-kinase) associates with Tie2 and that this association confers functional lipid kinase activity. Mutation of tyrosine 1101 of Tie2 abrogated p85 association both in vitro and in vivo in yeast. Tie2 was found to activate PI3-kinase in vivo as demonstrated by direct measurement of increases in cellular phosphatidylinositol 3-phosphate and phosphatidylinositol 3, 4-bisphosphate, by plasma membrane translocation of a green fluorescent protein-Akt pleckstrin homology domain fusion protein, and by downstream activation of the Akt kinase. Activation of PI3-kinase was abrogated in these assays by mutation of Y1101 to phenylalanine, consistent with a requirement for this residue for p85 association with Tie2. These results suggest that activation of PI3-kinase and Akt may in part account for Tie2's role in both embryonic vascular development and pathologic angiogenesis, and they are consistent with a role for Tie2 in endothelial cell survival.
Tie2是一种内皮细胞特异性受体酪氨酸激酶，在正常胚胎血管发育和肿瘤血管生成中均不可或缺，并且被认为在血管维持中发挥作用。然而，负责Tie2功能的信号通路仍不清楚。在本报告中，我们证明磷脂酰肌醇3激酶（PI3激酶）的p85亚基与Tie2相关联，并且这种关联赋予了功能性脂质激酶活性。Tie2酪氨酸1101位点的突变在体外和酵母体内均消除了与p85的关联。通过直接测量细胞中磷脂酰肌醇3磷酸和磷脂酰肌醇3,4 - 二磷酸的增加、绿色荧光蛋白 - Akt普列克底物蛋白同源结构域融合蛋白的质膜转位以及Akt激酶的下游激活，发现Tie2在体内可激活PI3激酶。在这些实验中，将Y1101突变为苯丙氨酸可消除PI3激酶的激活，这与该残基对于p85与Tie2关联的必要性一致。这些结果表明，PI3激酶和Akt的激活可能部分解释了Tie2在胚胎血管发育和病理性血管生成中的作用，并且与Tie2在内皮细胞存活中的作用一致。
