Extramitochondrial OPA1 and adrenocortical function

Fülöp, László and Rajki, Anikó and Katona, Dávid and Szanda, Gergő and Spät, András (2013) Extramitochondrial OPA1 and adrenocortical function. MOLECULAR AND CELLULAR ENDOCRINOLOGY, 381 (1-2). pp. 70-79. ISSN 0303-7207

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Abstract

We have previously described that silencing of the mitochondrial protein OPA1 enhances mitochondrial Ca2+ 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 approximately 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), Ca2+ 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.

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