Multiple Roles of 25-Hydroxycholesterol in Lipid Metabolism, Antivirus Process, Inflammatory Response, and Cell Survival

Figure 3

The regulation of 25-HC in cholesterol metabolism. Transcriptional factor SREBP controls the rate-limiting enzyme HMGCR. When the cholesterol level is low, the SREBP is escorted by SCAP from ER to Golgi body, in which this complex is cleaved by site-1 protease (S1P) and site-2 protease (S2P), and then the SREBP is released. 25-HC retains SREBP in ER via binds to an anchor protein INSIG in ER and suppresses SREBP translocation. Furthermore, 25-HC promotes HMGCR ubiquitylation and proteasomal degradation. 25-HC can also promote the CYP7A1 expression via activating transcriptional factor LXRα.