Figure 4.

Import of sterols into mitochondria for steroidogenesis. (A) Upon binding of cholesterol the StAR precursor protein changes its conformation. StAR expression is regulated by cAMP. (B) StAR comes in contact with PKA, PAP7/ACBD3, and ACBD1 and is imported into the mitochondria with sterols bound. Upon interaction with TSPO, StAR induces changes in the OMM and a transduceosome is formed. This structure, which includes TSPO/VDAC of the OMM and ANT in the IMM, facilitates imports and maturation of StAR. (C) Upon arrival in the mitochondrial matrix, the mature StAR protein delivers cholesterol to CPY11A1 where it is converted to pregnenolone.