Mahabeleshwar Ganapati H, Feng Weiyi, Phillips David R, Byzova Tatiana V
Department of Molecular Cardiology, Joseph J. Jacobs Center for Thrombosis and Vascular Biology, NB50, The Cleveland Clinic Foundation, Cleveland, OH 44195, USA.
J Exp Med. 2006 Oct 30;203(11):2495-507. doi: 10.1084/jem.20060807. Epub 2006 Oct 9.
The process of postnatal angiogenesis plays a crucial role in pathogenesis of numerous diseases, including but not limited to tumor growth/metastasis, diabetic retinopathy, and in tissue remodeling upon injury. However, the molecular events underlying this complex process are not well understood and numerous issues remain controversial, including the regulatory function of integrin receptors. To analyze the role of integrin phosphorylation and signaling in angiogenesis, we generated knock-in mice that express a mutant beta3 integrin unable to undergo tyrosine phosphorylation. Two distinct models of pathological angiogenesis revealed that neovascularization is impaired in mutant beta3 knock-in mice. In an ex vivo angiogenesis assay, mutant beta3 knock-in endothelial cells did not form complete capillaries in response to vascular endothelial growth factor (VEGF) stimulation. At the cellular level, defective tyrosine phosphorylation in mutant beta3 knock-in cells resulted in impaired adhesion, spreading, and migration of endothelial cells. At the molecular level, VEGF stimulated complex formation between VEGF receptor-2 and beta3 integrin in wild-type but not in mutant beta3 knock-in endothelial cells. Moreover, phosphorylation of VEGF receptor-2 was significantly reduced in cells expressing mutant beta3 compared to wild type, leading to impaired integrin activation in these cells. These findings provide novel mechanistic insights into the role of integrin-VEGF axis in pathological angiogenesis.
出生后血管生成过程在众多疾病的发病机制中起着关键作用，这些疾病包括但不限于肿瘤生长/转移、糖尿病视网膜病变以及损伤后的组织重塑。然而，这一复杂过程背后的分子事件尚未得到充分理解，许多问题仍存在争议，包括整合素受体的调节功能。为了分析整合素磷酸化和信号传导在血管生成中的作用，我们构建了表达无法进行酪氨酸磷酸化的突变型β3整合素的基因敲入小鼠。两种不同的病理性血管生成模型显示，突变型β3基因敲入小鼠的新生血管形成受损。在体外血管生成试验中，突变型β3基因敲入内皮细胞在血管内皮生长因子（VEGF）刺激下不能形成完整的毛细血管。在细胞水平上，突变型β3基因敲入细胞中酪氨酸磷酸化缺陷导致内皮细胞的黏附、铺展和迁移受损。在分子水平上，VEGF在野生型内皮细胞中刺激VEGF受体-2与β3整合素形成复合物，但在突变型β3基因敲入内皮细胞中则不然。此外，与野生型相比，表达突变型β3的细胞中VEGF受体-2的磷酸化显著降低，导致这些细胞中的整合素激活受损。这些发现为整合素-VEGF轴在病理性血管生成中的作用提供了新的机制性见解。
