Abstract 15362: Checkpoint Kinase 1-Associated Senp2 S344 Phosphorylation Under Laminar Flow Attenuates Endothelial-Mesenchymal Transition and Atherogenesis

Aims: To investigate the role of Checkpoint Kinase 1 (CHK1)-associated SENP2 S344 phosphorylation in laminar flow (LF)-regulated Endothelial-Mesenchymal Transition (EndMT) inhibition and the underlying mechanisms. Methods: We generated deSUMOylation enzyme sentrin-specific isopeptidase 2 (SENP2) S343A (equivalent to human SENP2 S344) knock-in (KI) and endothelial cell (EC)-specific SENP2 knock-out (SENP2 EKO) mice to detect EC activation, EndMT, and atherogenesis in vitro and in vivo . We also performed next-generation RNA sequencing (RNA-seq) analysis in ECs derived from these mice. Results: LF, but not disturbed flow (DF), triggered SENP2 S344 phosphorylation through CHK1. The decreased ERK5- and p53-SUMOylation by LF was abolished in ECs derived from SENP2 S343A KI mice. Both EC apoptosis and VCAM-1 expression were upregulated in SENP2 S344A KI mice. The increased atherogenesis in SENP2 S344A KI was regulated by vascular, but not hematopoietic, cells based on bone marrow transplantation (BMT) study. CHK1 expression was decreased by ionizing radiation (IR), leading to an enhanced ERK5- and p53-SUMOylation as well as EC inflammation. RNA-seq analysis revealed the involvement of SENP2 S344 phosphorylation in changes of fibrotic phenotypes and EndMT-related genes. Further, SENP2 S344A point mutation prevented LF-regulated TGFbR1 SUMOylation inhibition in vitro, as well as hypercholesterolemia-induced EndMT in vivo. Discussions: These data revealed the unique role of CHK1-associated SENP2 S344 phosphorylation in not only LF-regulated EndMT inhibition but also IR-associated EndMT activation and the subsequent atherogenesis. Maintaining CHK1-associated SENP2 S344 phosphorylation can be an ideal approach to mitigate EndMT, which is important in tumor radio-resistance as well as IR-associated cardiovascular disease.