SUN-191 Stress Opens Tim23 Complex Resulting Faster Steroid Metabolism

Abstract

The movement and distribution of mitochondria is essential for cellular function in response to physiological demand. Thus, coordinated mitochondrial action is necessary in cell development. The molecular basis of mitochondrial redistribution depends on the different steps of protein folding as the rapid burst of movements is interrupted by variables, including environmental and hormonal stressors, such as adrenocorticotropic hormone (ACTH). In adrenal and gonads, CYP11A1, catalyzes cholesterol to pregnenolone conversion. During stress, the ER and mitochondria comes close to each other, resulting in the formation of a complex consisting of the translocase of outer mitochondrial membrane 22, steroidogenic acute regulatory protein and 3β-hydroxysteroid dehydrogenase type 2 (3βHSD2) via its intermembrane space exposed charged unstructured loop region. An excess of ACTH inhibits organelle organization and fiber formation as visualized by transmission electron microscopy. We created stress in cells by depriving serum. Next isolation of mitochondrial complex with digitonin and analysis through a native-gradient PAGE formed a 400-kDa complex in the absence of serum. However an additional complex of 650 kDa was observed with serum. Western staining of the stressed cells with Tom22, 3βHSD2 and Tim23 antibodies independently showed several fold increase in expression of Tim23 and 3βHSD2 after 8 hour and a three fold increase Tom 22 after 2 hour. The expression of mitochondrial VDAC2 or cytoplasmic calnexin was unchanged. We conclude that an increase in Tim23 expression possibly opens the TIM23 complex resulting rapid interaction with the MAM and ER proteins for faster metabolic activity.