Abstract 315: Augmentation Of Protein O -glcnacylation By Impaired Intracellular Calcium Homeostasis Promoted Vascular Calcification

Abstract

Vascular calcification is accelerated in patients with diabetes mellitus and increases risk of cardiovascular events and mortality. Wes have demonstrated elevated protein O -GlcNAcylation promotes vascular calcification in diabetes. Increased O -GlcNAcylation is linked to impaired calcium signaling, which is critical for the development of vascular calcification in both humans and animal models. The present studies determined the role of an important regulator for intracellular calcium homeostasis, the stromal interaction molecule 1 (STIM1), in regulating O -GlcNAcylation and vascular calcification. Deletion of STIM1 induced osteogenic differentiation and calcification of VSMC, which was associated with decreased expression of the SMC marker genes and increased expression of the key osteogenic transcription factor, Runx2. By generating a SMC-specific STIM1 ablation mouse model, we determined that STIM1 ablation induced vascular calcification in aortic rings cultured ex vivo and in diabetic mice injected with low-dose streptozotocin in vivo. The diabetic mide with SMC-specific STIM1 ablation also exhibited increased aortic Runx2 expression and aortic stiffness (pulse wave velocity). Mechanistically, we identified that STIM1 deficiency impaired calcium homeostasis in VSMC, increased activation of the Ca 2+ /calmodulin-dependent protein kinase II and elevation of protein O -GlcNAcylation. Increased O -GlcNAcylation by STIM1 deficiency was further demonstrated in aortic arteries from the SMC-specific STIM1 ablation mice. The essential role of O -GlcNAcylation in mediating STIM1 deficiency-induced VSMC calcification was determined using a specific inhibitor for the O -GlcNAc transferase (OGT), the enzyme adding O -GlcNAc onto proteins. Inhibition of OGT abolished STIM1 deficiency-induced elevation of O -GlcNAcylation and VSMC. In conclusion, our studies have demonstrated a causative effect of SMC-expressed STIM1 on vascular calcification and stiffness in diabetes. We have further identified a novel link connecting STIM1 deficiency-induced impairment of calcium homeostasis and elevation of protein O -GlcNAcylation in VSMC that promotes osteogenic differentiation and calcification of VSMC.