Figure 9.

Proposed model of DHCR14 and LBR expression linked to cellular cholesterol status. Under conditions of low cholesterol (top), TM7SF2 gene expression is up-regulated by SREBP-2, and LBR is constitutively expressed. In this scenario, both DHCR14 and LBR protein are active and contribute to cholesterol synthesis. When cholesterol levels are high (bottom), TM7SF2 gene expression is inhibited, and DHCR14 protein is degraded by the proteasome. LBR gene and protein remain at basal levels, and LBR becomes the main contributor to Δ14 reductase activity.