Overexpression of SCAP inhibits autophagy and promotes lipid accumulation in vascular smooth muscle cells

Abstract

Objective To determine the effect of sterol regulatory element binding proteins cleavage activating protein (SCAP) on foam cell formation in vascular smooth muscle cells (VSMCs). Methods LV-SCAP were constructed with LV-SCAP, and LV-Control group served as control. The expression of SCAP and its downstream protein nSREBP2 was detected with Western blotting. Oil red O staining was used to observe lipid accumulation after LDL treatment, and the contents of total cholesterol (TC) and triglycerides (TG) were measured by Microplate Reader. The autophagic vacuoles were detected with monodansyl cadaverine (MDC) staining. The protein levels of autophagy-related proteins LC3b, P62, and AMPK-mTOR pathway were detected by Western blotting. After rapamycin (Rapa), mTOR inhibitor, was used to treat LV-SCAP, Western blotting and oil red O staining were performed again to observe the changes in the autophagy and accumulation of lipid droplets. Results Compared with LV-Control group, the protein expression of nSREBP2 was increased after the infection of lentiviral vector (P < 0.05). LV-SCAP group also presented accelerated accumulation of lipid droplets and increased contents of TC and TG (P < 0.05), decreased formation of autophagic vacuoles, down-regulation of LC3b and up-regulation of P62, decreased level of p-AMPK/AMPK, and increased level of p-mTOR/mTOR (P < 0.05). Rapa treatment resulted in enhanced expression of LC3b and reduced level of P62 (P < 0.05), and decreased accumulation of lipid droplets (P < 0.05). Conclusion SCAP inhibits VSMCs autophagy through AMPK-mTOR signaling pathway, and promotes the foam cell formation to participate in the development of atherosclerosis.

Keywords

• sterol regulatory element binding proteins cleavage activating protein
• vascular smooth muscle cells
• autophagy
• ampk-mtor pathway