Steroid Receptor Coactivator-1-Deficient Mice Exhibit Altered Hypothalamic-Pituitary-Adrenal Axis Function
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0013-7227/06/$15.00/0 Endocrinology 147(3):1322–1332 Printed in U.S.A. Copyright © 2006 by The Endocrine Society doi: 10.1210/en.2005-0751 Steroid Receptor Coactivator-1-Deficient Mice Exhibit Altered Hypothalamic-Pituitary-Adrenal Axis Function Jonathon N. Winnay, Jianming Xu, Bert W. O’Malley, and Gary D. Hammer Departments of Molecular and Integrative Physiology (H.N.W., G.D.H.) and Internal Medicine (G.D.H.), Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48109-0678; and Department of Molecular and Cellular Biology, Baylor College of Medicine (J.X., B.W.O.), Houston, Texas 77030 Downloaded from https://academic.oup.com/endo/article/147/3/1322/2501069 by guest on 28 September 2021 Steroidogenic factor-1 (SF-1), has emerged as a critical nu- as well as a concomitant defect in glucocorticoid-mediated clear receptor regulating development and differentiation at feedback inhibition of the HPA axis. An examination of po- several levels of the hypothalamic-pituitary-steroidogenic tential compensatory mechanism(s) revealed an increase in axis. Although many coregulatory factors have been shown to adrenal weight, selective elevation of melanocortin 2 receptor physically and functionally interact with SF-1, the relative mRNA, and a coincident increase in SRC-2 and SRC-3 expres- importance of these interactions in SF-1 target tissues has not sion in SRC-1؊/؊ adrenals. A reduction in blood glucose was been thoroughly established. In this study we assessed roles observed in SRC-1؊/؊ mice after chronic stress, consistent of steroid receptor coactivator-1 (SRC-1) in hypothalamic-pi- with a generalized state of glucocorticoid resistance. Dexa- tuitary-adrenal (HPA) axis function using SRC-1-deficient methasone suppression tests confirmed a weakened ability of SRC-1؊/؊) mice in the absence or presence of SF-1 haploin- glucocorticoids to 1) elevate serum glucose levels and induce) sufficiency. Surprisingly, SRC-1 deficiency did not alter base- hepatic phosphoenolpyruvate carboxykinase transcription line HPA axis function or the acute rise in corticosterone after and 2) suppress pituitary proopiomelanocortin transcript lev- ACTH administration and failed to exacerbate adrenocortical els in SRC-1؊/؊ animals. Collectively, these data are consistent dysfunction in SF-1؉/؊ mice. However, after exposure to par- with an indispensable role for SRC-1 in mediating actions of :adigms of acute and chronic stress, SRC-1؊/؊ mice exhibited glucocorticoids in pituitary and liver. (Endocrinology 147 an elevation in serum corticosterone despite normal (nonsup- 1322–1332, 2006) pressed) ACTH, suggesting an increase in adrenal sensitivity LTHOUGH ORIGINALLY cloned as the transcription sponses, namely, the transcriptional activation of genes in- A factor responsible for the cAMP-dependent regula- volved in steroid biosynthesis. SF-1 is an indispensable tion of steroid hydroxylases in the adrenal cortex, the use of mediator of this process by virtue of its essential role in the gene-targeting approaches to examine the in vivo function of transcriptional regulation of major steroidogenic enzyme steroidogenic factor-1 (SF-1) have revealed additional roles genes, including cytochrome p450 cholesterol side-chain for this nuclear receptor in adrenal/gonadal organogenesis, cleavage enzyme (SCC) (9), 17␣-hydroxylase (10), 3-hy- pituitary gonadotrope expression, and migration of cell pop- droxysteroid dehydrogenase (11), and 21-hydroxylase (12). ulations during development of the ventromedial hypothal- Several additional genes involved in steroid biosynthesis amus as well as its traditional role as a transcriptional co- require SF-1 for their appropriate regulation, including the ordinator of genes involved in the steroid biosynthetic receptor for ACTH [melanocortin 2 receptor (Mc2r)] and the pathway (1–5). Human patients and mice harboring muta- steroidogenic acute regulatory protein (StAR), both early tions/deletions in the SF-1 gene present with various degrees determinants of steroid biosynthesis in the adrenal gland of adrenal insufficiency and/or sex reversal (6–8). (13–16). The mammalian stress response elicits a coordinated tran- The activation of target genes by nuclear receptors requires scriptional program within the adrenal cortex through the the regulated recruitment of a variety of coregulatory factors actions of the proopiomelanocortin (POMC)-derived peptide that intrinsically possess or recruit proteins with enzymatic hormone, ACTH. The binding of ACTH to its cognate G activities that alter the local chromatin environment in a protein-coupled receptor activates a variety of signaling cas- manner that favors promoter occupancy and the subsequent cades that collectively implement ACTH-dependent re- recruitment of RNA polymerase II. A variety of cofactors have been implicated in the coordinated regulation of the First Published Online December 8, 2005 ACTH-dependent transcriptional response based upon the Abbreviations: ChIP, Chromatin immunoprecipitation; GR, glucocor- ticoid receptor; HPA, hypothalamic-pituitary-adrenal; Mc2r, melano- ability of these proteins to physically and/or functionally cortin 2 receptor; NGFI-B, nerve growth factor IB; PEPCK, phosphoenol- interact with SF-1 to modulate gene transcription. Included pyruvate carboxykinase; POMC, proopiomelanocortin; SCC, cytochrome in this group of coregulators are general transcription factors p450 cholesterol side-chain cleavage enzyme; SF-1, steroidogenic fac- [specificity protein 1, Jun, transcription initiation factor IIB tor-1; SRC-1, steroid receptor coactivator-1; StAR, steroidogenic acute regulatory protein; Tpit, pituitary-specific T box factor; WT, wild type. (TFIIB), nuclear factor-1, CCAAT/enhancer-binding pro- tein-, and activating protein-1] (17–21), transcriptional core- Endocrinology is published monthly by The Endocrine Society (http:// www.endo-society.org), the foremost professional society serving the pressors [Dax-1 (dosage-sensitive sex reversal-adrenal hypo- endocrine community. plasia congenita critical region on the X-chromosome protein 1322 Winnay et al. • SRC-1-Deficient Mice Exhibit Altered HPA Axis Endocrinology, March 2006, 147(3):1322–1332 1323 1), DP103 (DEAD-box protein 103), Cops2 (COP9 constitu- Tween-20] for 30 min at room temperature. SRC-1, SRC-2, and SRC-3 tive photomorphogenic homolog subunit 2), RIP 140 (recep- rabbit polyclonal antibodies (Santa Cruz Biotechnology, Inc., Santa tor-interacting protein 140), and SMRT (silencing mediator of Cruz, CA) and nonimmune rabbit IgG (Pierce Chemical Co., Rockford, IL) were diluted 1:200 in blocking buffer and incubated overnight at 4 retinoic acid and thyroid hormone receptor)] (22–26) as well C. Sections were incubated with a biotin-conjugated goat antirabbit as a variety of general coactivators [E1A binding protein secondary antibody (1:250; Molecular Probes, Eugene, OR) for 30 min at p300/CBP (cAMP response element binding protein-binding room temperature, followed by incubation with streptavidin-conjugated protein), TReP 132 (transcriptional regulating factor 1), and fluorescein (1:400; Molecular Probes). Nuclei were counterstained with propidium iodide (1:4000; Kirkegaard & Perry Laboratories, Gaithers- p160 steroid receptor coactivator (SRC) family] (27–31). Sur- burg, MD) for 5 min at room temperature. After rinsing, coverslips were prisingly, the in vivo significance of these interactions within mounted with aqueous mounting medium. Sections were observed us- the context of the hypothalamic-pituitary-steroidogenic axis ing a OptiPhot-2 fluorescence microscope (Nikon, Melville, NY), and has not been thoroughly assessed despite the documented pictures were captured with Spot Advance software (Diagnostics In- involvement of coregulatory factor dysfunction in various struments, Inc., Sterling Heights, MI). Downloaded from https://academic.oup.com/endo/article/147/3/1322/2501069 by guest on 28 September 2021 states of hormone resistance and cancer (32–34). ACTH stimulation test Each member of the SRC family of coregulators has been shown to serve as a coactivator for SF-1 on a variety of Dexamethasone (Sigma-Aldrich Corp., St. Louis, MO) was reconsti- tuted in saline and injected ip at a dose of 5 g/g body weight at 1800 h adrenal-specific promoters. Gene-targeting approaches to the night before and at 0800 h the morning of the procedure. ACTH ablate each member of this family in mice has revealed re- (Peninsula Laboratories, Inc., Belmont, CA) was reconstituted in saline dundant functions as well as differential roles for each mem- and injected ip at a dose of 1 g/g body weight at 1000 h. Tail blood was ber in various endocrine systems (35). In this study, we collected at 0-, 15-, 30-, and 60-min intervals for determination of serum assessed the impact of SRC-1 deficiency on hypothalamic- corticosterone levels using a commercially available assay (ALPCO Di- agnostics, Windham, NH). Each group consisted of five to 13 animals. pituitary-adrenal (HPA) axis function to discern whether SRC-1 participates in SF-1-dependent adrenocortical func- Restraint stress tion in vivo. Adult male mice were subjected to restraint stress by placement in a Materials and Methods perforated 50-ml plastic conical tube. Blood was collected by performing retroorbital bleeds after 30 min. Serum ACTH and corticosterone were Experimental animals determined using commercially available assays (ALPCO Diagnostics). Each group consisted of nine to 13 animals. All experiments