MAPK and PKA participate in the JEG-3 cell steroidogenesis

The mechanism that controls placental progesterone (P4) synthesis involves a signaling cascade mediated by PKA and other kinases that have yet to be identified. Steroidogenesis in Leydig cells is regulated by the PKA and MAPK-ERK pathways.

To get a deeper understanding of the control of placental steroidogenesis, JEG-3 cells were cultured for 24 h with MAPK inhibitors U0126 and MEK162, or PKA inhibitor H89, followed by the addition of H89, U0126, or MEK162, respectively, and cultured for an additional 24 h. LDH release and MTT evaluated cytotoxicity and viability. Control cells were cultured with db-cAMP or 22-OH-cholesterol. ERK, pERK, and steroidogenic proteins were identified by western blot.

P4 synthesis was partially inhibited at the concentrations of U0126, MEK162, or H89 used. An additive inhibition was observed when JEG-3 cells were cultured in the presence of U0126 or MEK162 and complemented with H89. The addition of db-cAMP partially reestablishes the steroidogenesis in cells incubated with U0126, MEK162, or H89. pERK was undetected with MEK162, but a small amount of pERK was found with U0126. Changes in P450scc amount were observed in the presence of MAPK inhibitors. Mass spectrometry identified several kinases associated with mitochondria, including MAPK and PKA.

The results suggest that JEG-3 cells have at least two signal cascades, the MAPK-ERK and the PKA pathways, which are involved in mitochondrial steroidogenesis to produce P4. The effects of these pathways on mitochondrial steroidogenesis could be partially mediated by changes in the nuclear expression of steroidogenic proteins.