The β3-Integrin Binding Protein β3-Endonexin Is a Novel Negative Regulator of Hypoxia-Inducible Factor-1

Aims: Integrins are multifunctional heterodimeric adhesion receptors that mediate the attachment between a cell and the extracellular matrix or other surrounding cells. In endothelial cells, integrins can modulate cell migration and motility. In particular, beta 3-integrin is expressed in angiogenic vessels. Signal transduction by beta 3-integrins requires the recruitment of intracellular signaling molecules. beta 3-endonexin is a highly spliced molecule that has been identified as a beta 3-integrin binding protein. beta 3-endonexin isoforms are expressed in endothelial cells and have been suggested to act as shuttle proteins between the membrane and the nucleus. However, their functional role in angiogenesis is unclear. In this study, we investigated whether beta 3-endonexin isoforms are involved in endothelial angiogenic processes under hypoxia. Results: The overexpression of beta 3-endonexin isoforms decreased endothelial proliferation and tube formation under hypoxia, while the depletion of beta 3-endonexin by RNAi promoted angiogenic responses in vitro and in vivo. In hypoxia, beta 3-endonexin accumulated in the nucleus, and prevention of this response by depletion of beta 3-endonexin increased hypoxic activation and induction of the hypoxia-inducible factor (HIF)-1 and its target genes VEGF and PAI-1. beta 3-endonexin diminished nuclear factor kappa B (NF kappa B) activation and decreased NF kappa B binding to the HIF-1 alpha promoter under hypoxia, subsequently diminishing NF kappa B-dependent transcription of HIF-1 alpha under hypoxia. Innovation: Our results indicate for the first time that the overexpression of beta 3-endonexin can decrease hypoxic induction and activation of HIF-1 alpha and can prevent hypoxic endothelial proliferation and angiogenic responses. Conclusion: beta 3-endonexin can act as a novel anti-angiogenic factor specifically in the response to hypoxia due to its negative impact on the activation of HIF-1. Antioxid. Redox Signal. 20, 1964-1976.