Pathological angiogenesis is a hallmark of many diseases. Previously, we reported that orphan nuclear receptor TR3/Nur77 (human homolog, Nur77, mouse homolog) is a critical mediator of angiogenesis to regulate tumor growth and skin wound healing via down-regulating the expression of the junctional proteins and integrin â4. However, the molecular mechanism, by which TR3/Nur77 regulated angiogenesis, was still not completely understood. In this report by analyzing the integrin expression profile in endothelial cells, we found that the TR3/Nur77 expression highly increased the expression of integrins á1 and â5, decreased the expression of integrins á2 and â3, but had some or no effect on the expression of integrins áv, á3, á4, á5, á6, â1 and â7. In the angiogenic responses mediated by TR3/Nur77, integrin á1 regulated endothelial cell proliferation and adhesion, but not migration. Integrin â5 shRNA inhibited cell migration, but increased proliferation and adhesion. Integrin á2 regulated all of the endothelial cell proliferation, migration and adhesion. However, integrin â3 did not play any role in endothelial cell proliferation, migration and adhesion. TR3/Nur77 regulated the transcription of integrins á1, á2, â3 and â5, via various amino acid fragments within its transactivation domain and DNA binding domain. Furthermore, TR3/Nur77 regulated the integrin á1 promoter activity by directly interacting with a novel DNA element within the integrin á1 promoter. These studies furthered our understanding of the molecular mechanism by which TR3/Nur77 regulated angiogenesis, and supported our previous finding that TR3/Nur77 was an excellent therapeutic target for pathological angiogenesis. Therefore, targeting TR3/Nur77 inhibits several signaling pathways that are activated by various angiogenic factors.
Angiogenesis Inducing Agents Binding Sites