Inner mitochondrial translocase Tim50 interacts with 3?-hydroxysteroid dehydrogenase type 2 to regulate adrenal and gonadal steroidogenesis.

ABSTRACT: In the adrenals, testes, and ovaries, 3?-hydroxysteroid dehydrogenase type 2 (3?HSD2) catalyzes the conversion of pregnenolone to progesterone and dehydroepiandrostenedione to androstenedione. Alterations in this pathway can have deleterious effects, including sexual development impairment, spontaneous abortion, and breast cancer. 3?HSD2, synthesized in the cytosol, is imported into the inner mitochondrial membrane (IMM) by translocases. Steroidogenesis requires that 3?HSD2 acts as both a dehydrogenase and isomerase. To achieve this dual functionality, 3?HSD2 must undergo a conformational change; however, what triggers that change remains unknown. We propose that 3?HSD2 associates with IMM or outer mitochondrial membrane translocases facing the intermembrane space (IMS) and that this interaction promotes the conformational change needed for full activity. Fractionation assays demonstrate that 3?HSD2 associated with the IMM but did not integrate into the membrane. Through mass spectrometry and Western blotting of mitochondrial complexes and density gradient ultracentrifugation, we show that that 3?HSD2 formed a transient association with the translocases Tim50 and Tom22 and with Tim23. This association occurred primarily through the interaction of Tim50 with the N terminus of 3?HSD2 and contributed to enzymatic activity. Tim50 knockdown inhibited catalysis of dehydroepiandrostenedione to androstenedione and pregnenolone to progesterone. Although Tim50 knockdown decreased 3?HSD2 expression, restoration of expression via proteasome and protease inhibition did not rescue activity. In addition, protein fingerprinting and CD spectroscopy reveal the flexibility of 3?HSD2, a necessary characteristic for forming multiple associations. In summary, Tim50 regulates 3?HSD2 expression and activity, representing a new role for translocases in steroidogenesis.

SUBMITTER: Pawlak KJ 

PROVIDER: S-EPMC3234738 | biostudies-literature | 2011 Nov

REPOSITORIES: biostudies-literature