Notch2 Signaling Sensitizes Endothelial Cells to Apoptosis by Negatively Regulating the Key Protective Molecule Survivin

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Abstract
Notch signaling pathway controls key functions in vascular and endothelial cells (ECs) where Notch4 plays a major role. However, little is known about the contribution of other Notch receptors. This study investigated regulation of Notch2 and further examined its implication in EC dysfunction. Here, we provide evidence for a novel link between Notch and TNF signaling, where Notch2 is upregulated and activated in response to TNF. Forced expression of Notch2 intracellular domain in cultured ECs promotes apoptosis and allows the significant downregulation of several cell-death-related transcripts in a dose-dependent manner. In particular, activation of Notch2 led to a rapid decrease in survivin mRNA and protein expression, while survivin upregulation was obtained by the selective knockdown of Notch2 in ECs, indicating that survivin expression is controlled at the Notch level. Moreover, Notch2 silencing and ectopic expression of survivin, but not XIAP or Bcl2, rescued ECs from TNF and Notch2-mediated apoptosis, respectively. In conclusion, TNF signaling activates Notch2 that sensitizes ECs to apoptosis via modulation of the key apoptosis regulator survivin. Overall, our findings also indicate that specific Notch receptors control distinct functions in vascular cells and inflammatory cytokines contribute to this specificity.

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