Abstract MP45: The Roles Of Telomeric Repeat Binding Factor 2-interacting Protein (TERF2IP) K240 Sumoylation In Endothelial Cells On Atherogenesis

Background and Objectives: It is not yet clear how the pro-atherogenic signaling events in endothelial cells (ECs) such as those that lead to EC senescence, apoptosis and activation are interconnected and promote atherosclerotic plaque formation in the area exposed to disturbed blood flow (d-flow). TERF2IP, a member of the shelterin complex of the telomere, regulates all three pathological events. We investigated the role of TERF2IP K240 SUMOylation in the process of d-flow-induced atherosclerotic plaque formation. Methods and Results: We found that d-flow increased TERF2IP K240 SUMOylation in ECs and that it was suppressed by a p90RSK specific inhibitor, FMK-MEA. This SUMOylation was independent of TERF2IP S205 phosphorylation. The d-flow-induced senescence, DNA damage, and apoptosis were inhibited in ECs with TERF2IP depletion or point-mutated phosphorylation (S205A) and SUMOylation (K240R) sites. NF-κB activation induced by d-flow or overexpression of p90RSK was also significantly inhibited in ECs overexpressing the TERF2IP S205A phosphorylation mutant. However, cells overexpressing the TERF2IP K240R SUMOylation mutant showed no effect on the d-flow or p90RSK-medaited NF-κB activation. To determine the biological function of TERF2IP K240 SUMOylation, we generated TERF2IP K240R knock-in (KI) mice and examined d-flow-induced atherosclerotic plaque formation using partial left carotid ligation model mice fed a high-fat diet after AAV8-PCSK9 injection. We found no differences in body weights and cholesterol levels between TERF2IP K240R KI and wild type control (WT) mice, but plaque formation was significantly inhibited in the KI mice compared to WT animals (Oil Red O positive area (%): 19.0 +/- 12.5 (KI mice, n=8) vs 61.2 +/- 24.3 (WT mice, n=7), p = 0.0008). Bone marrow from WT mice were transplanted into KI and WT mice, which were then injected with AAV8-PCSK9 virus and fed a high-fat diet for 16 weeks, but we still found that plaque formation was inhibited in the KI mice. Conclusion: TERF2IP SUMOylation plays a role in in EC senescence but not in activation. The significant inhibition of plaque formation in the TERF2IP K240R KI mice is due to downregulation of TERF2IP SUMOylation in ECs not in myeloid cells.