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Temporal Effect of Adrenocorticotrophic Hormone on Adrenal Glucocorticoid Steroidogenesis: Involvement of the Transducer of Regulated Cyclic AMP‐Response Element‐Binding Protein Activity
Author(s) -
Spiga F.,
Liu Y.,
Aguilera G.,
Lightman S. L.
Publication year - 2011
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1111/j.1365-2826.2010.02096.x
Subject(s) - creb , medicine , endocrinology , cholesterol side chain cleavage enzyme , steroidogenic acute regulatory protein , corticosterone , cyclic amp response element binding protein , adrenal cortex , biology , adrenocorticotropic hormone , glucocorticoid , response element , chemistry , gene expression , transcription factor , hormone , cytochrome p450 , gene , biochemistry , promoter , metabolism
The availability of active steroidogenic acute regulatory protein (StAR) and side‐chain cleavage cytochrome P450 (P450scc) are rate‐limiting steps for steroidogenesis. Transcription of StAR and P450scc genes depends on cyclic AMP‐response element‐binding protein (CREB) phosphorylation and CREB co‐activator, transducer of regulated CREB activity (TORC), which is regulated by salt‐inducible kinase 1 (SIK1). In the present study, we investigated the relationship between TORC activation and adrenocorticotrophic hormone (ACTH)‐induced steroidogenesis in vivo, by examining the time‐course of the effect of ACTH injection (4 ng, i.v.) on the transcriptional activity of StAR and P450scc genes and the nuclear accumulation of transducer of regulated CREB activity 2 (TORC2) in rat adrenal cortex. ACTH produced rapid and transient increases in plasma corticosterone, with maximal responses between 5 and 15 min, and a decrease to almost basal values at 30 min. StAR and P450scc hnRNA levels increased 15 min following ACTH and decreased toward basal values at 30 min. Concomitant with an increase in nuclear phospho‐CREB, ACTH injection induced nuclear accumulation of TORC2, with maximal levels at 5 min and a return to basal values by 30 min. The decline of nuclear TORC2 was paralleled by increases in SIK1 hnRNA and mRNA 15 and 30 min after injection, respectively. The early rises in plasma corticosterone preceding StAR and P450scc gene transcription suggest that post‐transcriptional and post‐translational changes in StAR protein mediate the early steroidogenic responses. Furthermore, the direct temporal relationship between nuclear accumulation of TORC2 and the increase in transcription of steroidogenic proteins, implicates TORC2 in the physiological regulation of steroidogenesis in the adrenal cortex. The delayed induction of SIK1 suggests a role for SIK1 in the declining phase of steroidogenesis.