Regulation of c-fos, c-jun and jun-B messenger ribonucleic acids by angiotensin-II and corticotropin in ovine and bovine adrenocortical cells.

Abstract

Previous work has shown that corticotropin (ACTH) and angiotensin-II (A-II), in addition to their acute steroidogenic effects, exert long-term influences on adrenal cell differentiated function, stimulatory or inhibitory, respectively. Certain nuclear proto-oncogenes have been implicated in the regulation of gene expression in many cell systems. We have investigated the effects of ACTH and A-II on the levels of c-fos, c-jun, and jun-B messenger RNAs (mRNAs), in bovine and ovine (OAC) adrenal fasciculata cells. In both cell types ACTH produced time- (maximum at 1 h) and dose-dependent (ED50 congruent to 10(-12) M) increase in c-fos (2- to 4-fold) and jun-B (10- to 20-fold) mRNA levels but did not affect c-jun. The concentrations required to induce half-maximal mRNA accumulation and cortisol production were similar. A-II also produced a dose-dependent increase in c-fos and jun-B mRNAs but also in c-jun in both cell types, despite the fact that OAC are resistant to the steroidogenic action of the hormone. The stimulatory effects of A-II on c-fos mRNA were higher than those produced by ACTH, whereas the effects on jun-B were similar but ACTH abolished (OAC) or decreased (bovine adrenal fasciculata cells) the stimulatory effects of A-II on c-jun mRNA. The effects of ACTH and A-II on cortisol production and proto-oncogene mRNAs were in part mimicked by 8 Bromo-cAMP and the phorbol ester phorbol-12-myristate-13 acetate plus calcium ionophore A23187, respectively. In the presence of cycloheximide, which blocks the steroidogenic effects of both hormones, proto-oncogene mRNAs were superinduced by both hormones. This result, together with the fact that dexamethasone failed to affect the mRNA levels suggests that the stimulatory effects of ACTH and A-II on proto-oncogene expression were not related to an autocrine/intracrine action of cortisol. Taken together, these findings show that the proto-oncogene mRNAs in normal adrenal cells are regulated by ACTH and A-II, acting through different intracellular pathways. They also demonstrate differential responsiveness of the Jun family to both hormones. Thus, the opposite long-term action of ACTH and A-II on adrenal cell differentiated function could be mediated by its different initial effects on proto-oncogene expression, in particular in the members of the Jun family.

Angiotensin‐II‐induced expression of proto‐oncogene (c‐fos, jun‐B and c‐jun) mRNA in bovine adrenocortical fasciculata cells (BAC) is mediated by AT‐1 receptors

“…Thus, both sets of experimental approaches indicate that the stimulatory action of A-II on proto-onco- gene mRNA levels is mainly mediated through activation of PKC. Although the acute effects of A-II on both steroid production and proto-oncogene mRNA levels are mediated by the AT-1 receptor subtype, the effects are unrelated since inhibitors of protein synthesis block the stimulation of steroidogenesis by A-II but potentiate its effects on proto-oneogene mRNA [9]. In addition to these acute effects, A-11 has a long-term inhibitory effect on the differentiated functions of BAC by inducing a down-regulation of its own receptors [16,17].…”

“…BAC were prepar~ by sequential treatment of adrenal cortical flices with trypsin (0.19%) as previously der~eribcd [8,9]. The o:lls were ctdtured in a chemically defined medium, Ham's FI~DMEM {1:1), containin~ tranfferrin (10#~ml), insulin (5/~ffml), vitamin C ( 10 -'~ M) ,And .L.n!ihintie,~ The experiments were carried out on ceils ¢ullttred for three &tys.…”

“…'tt 80°C to cross-link the RNA to the filters. Hybridization with complementary DNA "~P-labdlmd probes and the analyais of blots were curried out as previously described [9].…”

Cerebellin and des-cerebellin exert ACTH-like effects on corticosterone secretion and the intracellular signaling pathway gene expression in cultured rat adrenocortical cells - DNA microarray and QPCR studies

“…The Fos gene belongs to mitogenic, CREB, calcium and protein kinase C, phospholipase C, and stress intracellular signaling pathways. The ubiquitously-expressed fos gene is a proto-oncogene that encodes leucine zipper proteins that dimerize with proteins of the Jun family, thereby forming the transcription factor complex AP-1 (42). As such, the Fos proteins were implicated as regulators of cell proliferation, Table III.…”

Cloning of ACTH-regulated genes in the adrenal cortex

“…Many of these effects depend on changes in the expression of specific genes that encode structural and regulatory proteins and enzymes. ACTH and other trophic hormones have been shown to enhance the expression of protooncogenes within <60 min and of steroidogenic enzymes within hours [4][5][6]. The present study was initiated to examine the scope of ACTH effects on the expression of other genes in adrenocortical cells.…”