title: Protein kinase C-induced activin A switches adrenocortical steroidogenesis to aldosterone by suppressing CYP17A1 expression.
abstract: Functional zonation of the adrenal cortex is a consequence of the zone-specific expression of P450c17 (CYP17A1) and its cofactors. Activin and inhibin peptides are differentially produced within the zones of the adrenal cortex and have been implicated in steroidogenic control. In this study, we investigated whether activin and inhibin can function as intermediates in functional zonation of the human adrenal cortex. Activin A suppressed CYP17A1 expression and P450c17 function in adrenocortical cell lines as well as in primary adrenal cell cultures. Inhibin βA-subunit mRNA and activin A protein levels were found to be increased up to 1,900-fold and 49-fold, respectively, after protein kinase C (PKC) stimulation through PMA or angiotensin II in H295R adrenocortical carcinoma cells. This was confirmed in HAC15 cells and for PMA in primary adrenal cell cultures. Both PMA and Ang II decreased CYP17A1 expression in the adrenocortical cell lines, whereas PMA concurrently suppressed CYP17A1 levels in the primary cultures. Inhibition of activin signaling during PKC stimulation through silencing of the inhibin βA-subunit or blocking of the activin type I receptor opposed the PMA-induced downregulation of CYP17A1 expression and P450c17 function. In contrast, PKA stimulation through adrenocorticotrophin or forskolin increased expression of the inhibin α-subunit and betaglycan, both of which are antagonists of activin action. These data indicate that activin A acts as a PKC-induced paracrine factor involved in the suppression of CYP17A1 in the zona glomerulosa and can thereby contribute to functional adrenocortical zonation.
authors.affiliation: Department of Internal Medicine.
authors.forename: Johannes
authors.initials: J
authors.lastname: Hofland
authors.forename: Jacobie
authors.initials: J
authors.lastname: Steenbergen
authors.forename: Leo J
authors.initials: LJ
authors.lastname: Hofland
authors.forename: Peter M
authors.initials: PM
authors.lastname: van Koetsveld
authors.forename: Marco
authors.initials: M
authors.lastname: Eijken
authors.forename: Francien H
authors.initials: FH
authors.lastname: van Nederveen
authors.forename: Geert
authors.initials: G
authors.lastname: Kazemier
authors.forename: Wouter W
authors.initials: WW
authors.lastname: de Herder
authors.forename: Richard A
authors.initials: RA
authors.lastname: Feelders
authors.forename: Frank H
authors.initials: FH
authors.lastname: de Jong
mesh_terms: D028341:Activins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D000302:Adrenal Cortex / Q000187:drug effects / Q000378:metabolism*; D000735:Androstenedione / Q000096:biosynthesis; D000804:Angiotensin II / Q000494:pharmacology; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D006801:Humans; D006854:Hydrocortisone / Q000096:biosynthesis; D007265:Inhibins / Q000235:genetics / Q000378:metabolism; D011374:Progesterone / Q000096:biosynthesis; D011493:Protein Kinase C / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013254:Steroid 17-alpha-Hydroxylase / Q000235:genetics* / Q000378:metabolism; D015384:Zona Glomerulosa / Q000378:metabolism
chemical_list: C422405:activin A; D028341:Activins; D000804:Angiotensin II; D000735:Androstenedione; D011374:Progesterone; D007265:Inhibins; C501892:CYP17A1 protein, human; D013254:Steroid 17-alpha-Hydroxylase; D011493:Protein Kinase C; D006854:Hydrocortisone
keywords: 17α-hydroxylase/17,20 lyase; activin; adrenocortical zonation; steroidogenesis