We have previously described that silencing of the mitochondrial protein OPA1 
enhances mitochondrial Ca(2+) signaling and aldosterone production in H295R 
adrenocortical cells. Since extramitochondrial OPA1 (emOPA1) was reported to 
facilitate cAMP-induced lipolysis, we hypothesized that emOPA1, via the enhanced 
hydrolysis of cholesterol esters, augments aldosterone production in H295R 
cells. A few OPA1 immunopositive spots were detected in ∼40% of the cells. In 
cell fractionation studies OPA1/COX IV (mitochondrial marker) ratio in the 
post-mitochondrial fractions was an order of magnitude higher than that in the 
mitochondrial fraction. The ratio of long to short OPA1 isoforms was lower in 
post-mitochondrial than in mitochondrial fractions. Knockdown of OPA1 failed to 
reduce db-cAMP-induced phosphorylation of hormone-sensitive lipase (HSL), Ca(2+) 
signaling and aldosterone secretion. In conclusion, OPA1 could be detected in 
the post-mitochondrial fractions, nevertheless, OPA1 did not interfere with the 
cAMP - PKA - HSL mediated activation of aldosterone secretion.