Summary of the proposed mechanisms for the association of StAR to the OMM in MA-10 Leydig cells following hormone stimulation.

<p>After hormone stimulation, mitochondrial fusion induction through Mfn2 up-regulation in mitochondria is needed for increasing StAR mRNA levels. Also, mitochondrial fusion is required post-transcriptionally for StAR localization at the OMM and subsequent binding to a cholesterol molecule. Then, cholesterol-bound StAR is available for ERK and PKA mitochondrial phosphorylation, increasing its activity and cholesterol transport. After the 2 h temporal frame of ERK activity, StAR is dephosphorylated, de-activated and translocated to the mitochondrial matrix where it is degraded by mitochondrial proteases. Abbreviations: pERK1/2 (phospho-ERK1/2), pStAR: chol (phospho-StAR bound to a cholesterol molecule), PKA(c) (PKA catalytic subunit), StAR (m) (StAR in the mitochondrial matrix).