Abstract 234: Nuclear Export of Telomeric Repeat Binding Factor 2 (terf2)-interacting Protein (terf2ip) Expression, One of the Sherterin Complex Molecule, is Crucial for Disturbed Flow-induced Endothelial Inflammation and Senescence via Upregulating Terf2ip S205 Phosphorylation

Atherosclerosis is a multifactorial disease mainly caused by endothelial cell (EC) dysfunction resulting from EC senescence. Both EC inflammation and senescence are increased by disturbed flow (d-flow) but the exact mechanism is still unknown. The potential role of TERF2IP in regulating inflammation has been reported, but it has been controversial, especially in ECs. We found that d-flow-induced NF-kB activation was significantly inhibited by the depletion of TERF2IP, but TNF-induced NF-kB activation under laminar flow (l-flow) was not inhibited by TERF2IP depletion. TERF2IP S205 phosphorylation was increased by d-flow, but not by s-flow. This TERF2IP S205 phosphorylation was crucial for d-flow-induced TERF2IP nuclear export, which also caused nuclear export of its binding partner TERF2 in a piggy-back manner. Both the depletion of TERF2IP (TERF2IP siRNA) and overexpression of TERF2IP S205A mutant inhibited d-flow-induced TERF2 nuclear export as well as subsequent EC senescence. In addition, we found the key role of p90RSK activation in regulating EC inflammation and senescence via TERF2IP S205 phosphorylation. To determine the role of TERF2IP and TERF2 cellular localization in vivo, we performed in vivo en face immunostaining of mouse aortic arch in EC specific TERF2IP knock out (EC-TERF2IP-KO) and control mice using anti-TERF2IP or TEFR2 and anti-VE-cadherin antibodies. In control mice TERF2IP expression was very low in the l-flow area. In contrast we found a significant increase of TERF2IP expression, especially in the extra-nuclear region of ECs in the d-flow area. More nuclear localization of TERF2 was observed in EC-TERF2IP-KO mice than those in wild type, which supports our finding in vitro. Significant decreases of VCAM-1 expression and apoptosis were found in the d-flow area in EC-TERF2IP-KO mice compared to control mice. Lastly, we found a significant decrease in d-flow-induced atherosclerotic plaque formation after partial carotid ligation in EC-TERF2IP-KO mice crossed with Ldlr-/- mice compared to control Ldlr-/- mice. These data suggest the key role of nuclear export of TERF2IP in up-regulating EC inflammation and senescence via p90RSK-mediated TERF2IP S205 phosphorylation.