Scarlett Kisha, Pattabiraman Vaishnavi, Barnett Petrina, Liu Dong, Anderson Leonard M
From the Cardiovascular Research Institute and.
the Cancer Center for Therapeutic Development, Clark Atlanta University, Atlanta, Georgia 30314.
J Biol Chem. 2015 Mar 6;290(10):6303-15. doi: 10.1074/jbc.M114.601146. Epub 2014 Dec 15.
Angiogenesis is a dynamic process required for embryonic development. However, postnatal vascular growth is characteristic of multiple disease states. Despite insights into the multistep process in which adhesion molecules, extracellular matrix proteins, growth factors, and their receptors work in concert to form new vessels from the preexisting vasculature, there remains a lack of insight of the nuclear transcriptional mechanisms that occur within endothelial cells (ECs) in response to VEGF. Iroquois homeobox gene 3 (Irx3) is a transcription factor of the Iroquois family of homeobox genes. Irx homeodomain transcription factors are involved in the patterning and development of several tissues. Irx3 is known for its role during embryogenesis in multiple organisms. However, the expression and function of Irx3 in human postnatal vasculature remains to be investigated. Here we show that Irx3 is expressed in human microvascular endothelial cells, and expression is elevated by VEGF stimulation. Genetic Irx3 gain and loss of function studies in human microvascular endothelial cells resulted in the modulation of EC migration during wound healing, chemotaxis and invasion, and tubulogenesis. Additionally, we observed increased delta-like ligand 4 (Dll4) expression, which suggests an increase in EC tip cell population. Finally, siRNA screening studies revealed that transient knockdown of Hey1, a downstream Notch signaling mediator, resulted in increased Irx3 expression in response to VEGF treatment. Strategies to pharmacologically regulate Irx3 function in adult endothelial cells may provide new therapies for angiogenesis.
血管生成是胚胎发育所必需的动态过程。然而，出生后血管生长是多种疾病状态的特征。尽管对粘附分子、细胞外基质蛋白、生长因子及其受体协同作用以从现有脉管系统形成新血管的多步骤过程有了深入了解，但对于内皮细胞（ECs）中响应血管内皮生长因子（VEGF）而发生的核转录机制仍缺乏深入了解。易洛魁同源框基因3（Irx3）是易洛魁同源框基因家族的转录因子。Irx同源结构域转录因子参与多种组织的模式形成和发育。Irx3因其在多种生物体胚胎发生过程中的作用而闻名。然而，Irx3在人类出生后脉管系统中的表达和功能仍有待研究。在这里，我们表明Irx3在人微血管内皮细胞中表达，并且VEGF刺激可使其表达升高。在人微血管内皮细胞中进行的Irx3功能获得和缺失的遗传学研究导致了伤口愈合过程中内皮细胞迁移、趋化性和侵袭以及管状形成的调节。此外，我们观察到δ样配体4（Dll4）表达增加，这表明内皮细胞尖端细胞群体增加。最后，小干扰RNA（siRNA）筛选研究表明，下游Notch信号介导因子Hey1的瞬时敲低导致VEGF处理后Irx3表达增加。在成年内皮细胞中通过药理学方法调节Irx3功能的策略可能为血管生成提供新的治疗方法。
