Endothelial Yin Yang 1 Phosphorylation at S118 Induces Atherosclerosis Under Flow

Rationale: Disturbed flow occurring in arterial branches and curvatures induces vascular endothelial cell (EC) dysfunction and atherosclerosis. We postulated that disturbed flow plays important roles in modulating phosphoprotein expression profiles to regulate endothelial functions and atherogenesis. Objective: The goal of this study is to discover novel site-specific phosphorylation alterations induced by disturbed flow in ECs to contribute to atherosclerosis. Methods and Results: Quantitative phosphoproteomics analysis of ECs exposed to disturbed flow with low and oscillatory shear stress (OS, 0.5plusminus4 dynes/cm2) vs. pulsatile flow with high shear stress (PS, 124plusminus dynes/cm2) revealed that OS induces serine (S)118 phosphorylation of Yin Yang 1 (phospho-YY1S118) in ECs. Elevated phospho-YY1S118 level in ECs was further confirmed to be present in the disturbed flow regions in experimental animals and human atherosclerotic arteries. This disturbed flow-induced EC phospho-YY1S118 is mediated by casein kinase 2α (CK2α) through its direct interaction with YY1. Yeast two-hybrid library screening and in situ proximity ligation assays demonstrate that phospho-YY1S118 directly binds zinc finger with KRAB and SCAN domains 4 (ZKSCAN4) to induce promoter activity and gene expression of human double minute 2 (HDM2), which consequently induces EC proliferation through down-regulations of p53 and p21CIP1. Administration of apolipoprotein E-deficient (ApoE-/-) mice with CK2-specific inhibitor tetrabromocinnamic acid or atorvastatin inhibits atherosclerosis formation through down-regulations of EC phospho-YY1S118 and HDM2. Generation of novel transgenic mice bearing EC-specific overexpression of S118-non-phosphorylatable mutant of YY1 in ApoE-/- mice confirms the critical role of phospho-YY1S118 in promoting atherosclerosis through EC HDM2. Conclusions: Our findings provide new insights into the mechanisms by which disturbed flow induces endothelial phospho-YY1S118 to promote atherosclerosis, thus indicating phospho-YY1S118 as a potential molecular target for atherosclerosis treatment.