Abstract 939: Mdm2 Induces Vascular Calcification Through Its E3 Ligase Activity

Abstract

Rationale: Calcium deposition to the vascular smooth muscle matrix, or vascular calcification (VC), makes vessels rigid, increasing morbidity and mortality in patients with cardiovascular and renal diseases. Previously, we suggested that histone deacetylase (HDAC) 1 prevents VC, whereas its E3 ligase, mouse double minute 2 homolog (MDM2), exaggerates VC by inducing the polyubiquitination of HDAC1. Objective: In the present study, we extend our results to investigate whether MDM2-induced VC is dependent on its ubiquitination activity. Methods and Results: Using cellular and animal models with genetically engineered mice, we observed that vascular smooth muscle cell-specific conditional knockout of Mdm2 blunted vitamin D3-induced VC. We generated both MDM2 Y489A, which lacks ubiquitination activity, and MDM2 ΔR, a RING domain-deleted truncated mutant. Compared with the activity of wild-type (WT) MDM2, the HDAC1-ubiquitination activities of both Y489A and ΔR were significantly reduced. WT MDM2 potentiated inorganic phosphate-induced VC by inducing runt-related transcription factor 2 (Runx2), whereas Y489A and ΔR failed to do so. We generated three different transgenic lines to overexpress WT, Y489A, and ΔR MDM2. TgMDM2 WT elicited calcium deposition, whereas TgMDM2 Y489A and TgMDM2 ΔR did not. Conclusions: Taken together, our results suggest that MDM2-induced VC is dependent on the ubiquitination activity of MDM2 to degrade HDAC1. Accordingly, blockade of MDM2 ubiquitination activity might have beneficial effects in the treatment of VC.