Acute regulation of the bovine gene for the steroidogenic acute regulatory protein in ovarian theca and adrenocortical cells

Abstract

Upregulation of the steroidogenic acute regulatory protein (StAR) is implicated in the rapid synthesis and secretion of steroidogenic cells to produce steroids in response to stimulation by trophic hormones of the gonadal and stress axes. In the present study, we have assessed the kinetics of both StAR gene transcription and protein biosynthesis in primary cell cultures of bovine adrenocortical and ovarian theca cells, under conditions of acute stimulation by corticotrophin (ACTH) and luteinizing hormone (LH), respectively. In both cell systems, detectable upregulation of StAR gene transcription occurred within 1-2 h, reaching maxima at 4 h (theca cells) or 6 h (adrenocortical cells). mRNA levels returned rapidly to baseline, by 12 h or 24 h, respectively. Specific StAR protein levels were assessed by western blotting using a novel antibody raised against a bovine StAR peptide, and showed a similar fast upregulation, albeit delayed by 1-2 h compared with the mRNA. The response of the cultured theca cells was more acute than that of the adrenocortical cells, possibly reflecting the propensity of the LH receptor to desensitize rapidly, unlike the ACTH receptor. The primary bovine theca cell cultures were also used for fully homologous transfection studies using various deletion promoter-reporter constructs of the bovine StAR gene. Kinetic analysis of the results indicated that the acute transcriptional response resides within the proximal (-315 bp) promoter region, which includes two putative responsive elements for the steroidogenic factor-1. More distal promoter regions may be involved in modulating the specificity of expression by combining enhancer and inhibitory functions.

Stress-induced regulation of steroidogenic acute regulatory protein expression in head kidney of Gilthead seabream (Sparus aurata)

“…It also agrees with the previous data found in the same species, S. aurata, in our laboratory (Rotllant et al 2001, Ganga et al 2006 showing that ACTH caused a rapid increase in cortisol levels in superfused head kidney tissue. In addition, our results on StAR expression correlate with data from mammals showing that acute in vivo or in vitro treatment with ACTH leads to a rapid and significant increase (between 1 and 3 h after the treatment) in StAR mRNA in the adrenals (Ariyoshi et al 1998, Ivell et al 2000, Le Roy et al 2000. The results are also similar to other fish species, such as eel, where Li et al (2003) found that ACTH injection increased StAR mRNA levels 1 .…”

“…In mammals, ACTH induces a rapid increase in corticosteroid synthesis and a longer term chronic cyclic AMP (cAMP)/protein kinase A (PKA)-based response that affects both the transcription and translation of several genes encoding for steroidogenic enzymes (reviewed by Sewer & Waterman 2003). In addition, in mammals a very rapid increase in both StAR mRNA (Fleury et al 1996, Ivell et al 2000, Le Roy et al 2000 and StAR protein (Nishikawa et al 1996; reviewed by Lehoux et al 2003) occurs in response to ACTH. Moreover, plasma cortisol has been found to mirror levels of StAR mRNA (Ariyoshi et al 1998, Le Roy et al 2000 and StAR protein , Nishikawa et al 1996.…”

Involvement of Protein Kinase C and Cyclic Adenosine 3′,5′-Monophosphate-Dependent Kinase in Steroidogenic Acute Regulatory Protein Expression and Steroid Biosynthesis in Leydig Cells1

“…It was also noted that PMA-responsive elements were likely present within the Ϫ151/Ϫ110 region of the Star promoter. Also, the activity of the Ϫ966/Ϫ1 promoter construct was always lower than those of the Ϫ254/ Ϫ1 or Ϫ151/Ϫ1 constructs, a pattern previously observed [32,33]. This unexplained observation could indicate the presence of an inhibitory element between Ϫ966 and Ϫ254 in the Star promoter.…”

In humans, early cortisol biosynthesis provides a mechanism to safeguard female sexual development

“…For brightfield dual IHC, the Vector Red kit was used according to the manufacturer's instructions (Vector Laboratories). All antibodies to steroidogenic enzymes have been reported previ- ously with control data (10,(28)(29)(30)(31)(32)(33)(34)(35)(36). In the current experiments, controls included omission of primary or secondary antibody.…”