In vivo effects of adrenocorticotrophin on the expression of the hamster steroidogenic acute regulatory protein

Abstract

In this study, we report the cDNA cloning of hamster adrenal steroidogenic acute regulatory (StAR) protein and the effect of adrenocorticotrophin (ACTH) on its expression in vivo. A hamster adrenal cDNA library was screened using an 852 bp fragment obtained by polymerase chain reaction; this fragment corresponds to the entire coding sequence (CDS) of the hamster adrenal StAR cDNA. Ten clones of different lengths were isolated and sequenced. The longest clone was 1564 bp and contained 34 bp in the 5 -untranslated region, 852 bp in the CDS, and 678 bp in the 3 -untranslated region (3 -UTR). Two polyadenylation signal sequences were found in the 3 -UTR. The CDS of the ten isolated clones was identical, but six of these lacked the last 132 nucleotides in the 3 -UTR, thus indicating that they had used the first polyadenylation signal. The hamster StAR protein contains 284 amino acid residues, and is 91·9% homologous to mouse, 90·5% to rat, 86·4% to human, 85% to porcine, and 82·5% to bovine StAR protein. Southern blot analysis indicated the presence of only one StAR gene in the hamster genome. Northern blotting analysis revealed the presence of the StAR mRNA in male and female steroidogenic tissues, namely adrenals and gonads, but not in the liver or in the kidneys of either sex. Three mRNA species of 1·7, 3·1 and 5·3 kb were found in whole hamster adrenals. Administration of ACTH to hamsters provoked increases (two-to threefold) in the adrenal content of the StAR mRNA within 1 h in vivo. Western blotting analysis on adrenal mitochondria showed that the level of StAR protein was also significantly elevated (1·5-fold) 1 h after ACTH treatment.

Stirring Up New Ideas About the Regulation of the Hypothalamic-Pituitary-Interrenal Axis in Zebrafish (Danio rerio)

“…10,41 In mammals, studies have demonstrated that changes in the adrenal expression of star results in increases in StAR protein. 43,44 The changes in star mRNA expression observed in this study reflect the pattern of whole-body cortisol, supporting the idea that StAR is an important component of the acute stress response in zebrafish. Moreover, the transient nature of the response suggests that the timing of sampling in relation to the stressor may be critical to defining the transcriptional contribution of star to the stress response.…”

Developmental Changes in Adrenocorticotrophin (ACTH)-Induced Expression of ACTH Receptor and Steroid Acute Regulatory Protein mRNA in Ovine Fetal Adrenal Cells

“…?3 Moreover, it has been reported in the hamster that administration of ACTH induces a rapid increase in adrenal StAR mRNA and protein, thus further emphasizing the regulatory importance of ACTH in vivo. 33 We did not assess the expression of any steroidogenic enzymes in this study. It is quite probable the expression levels of some of these enzymes increased after ACTH exposure, and contributed to the increased output.…”

Phosphorylation and function of the hamster adrenal steroidogenic acute regulatory protein (StAR)

“…We have demonstrated that ACTH administration [14,15] and sodium restriction [16] in vivo affected the formation of different species of StAR in rat [14,16,17] and hamster [14] adrenals.…”

“…Since the original report on the mouse StAR [1], StAR was cloned from 13 other animal species including the hamster [15]. By alignment analysis of the amino acid sequences of all these StARs, we have found conserved putative phosphorylation sites among most animal species.…”

“…StAR sequences of man [25], horse [26], pig [27], sheep [28], cow [29], rat [30], mouse [1], hamster [15], chicken [31], frog [31], zebra fish [31], rainbow trout [32], brook trout [32], eel [33] and cod [34] were obtained from Genbank and aligned with ClustalW at http://www.ebi.ac.uk. Putative phosphorylation sites were determined using PhosphoBase v2.0, a database of phosphorylation sites provided by the Center for Biological Sequence Analysis at the Technical University of Denmark (http://www.cbs.dtu.dk/databases/PhosphoBase).…”