Mechanisms of cholesterol transfer to adrenal mitochondria. Steroidogenic cholesterol in adrenal cells transfers to PBR and then StAR in the mitochondria from the plasma membrane. Cholesterol is taken up from both LDL receptors and apoA/HDL receptors (SR-BI) in caveolin-rich (Cav-rich) domains. Late endosomes mediate this transfer to the mitochondria via the activities of NPC-1 (which is inhibited by U18666A) and possibly the StAR-like protein MLN64. Acyl-CoA:cholesterol acyltransferase (ACAT) converts free cholesterol derived from organelles (e.g., endosomes and endoplasmic reticulum (ER)) to the CEs that represent the predominant components of lipid droplets. Blue arrows indicate the routing of cholesterol into and through the cell. StAR is represented at the OMM and IMM, respectively, in its p37 and p30 forms.