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Jiang Z, Elsarrag SZ, Duan Q, LaGory EL, Wang Z, Alexanian M, McMahon S, Rulifson IC, Winchester S, Wang Y, Vaisse C, Brown JD, Quattrocelli M, Lin CY, Haldar SM. KLF15 cistromes reveal a hepatocyte pathway governing plasma corticosteroid transport and systemic inflammation. SCIENCE ADVANCES 2022; 8:eabj2917. [PMID: 35263131 PMCID: PMC8906731 DOI: 10.1126/sciadv.abj2917] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2021] [Accepted: 01/13/2022] [Indexed: 05/15/2023]
Abstract
Circulating corticosteroids orchestrate stress adaptation, including inhibition of inflammation. While pathways governing corticosteroid biosynthesis and intracellular signaling are well understood, less is known about mechanisms controlling plasma corticosteroid transport. Here, we show that hepatocyte KLF15 (Kruppel-like factor 15) controls plasma corticosteroid transport and inflammatory responses through direct transcriptional activation of Serpina6, which encodes corticosteroid-binding globulin (CBG). Klf15-deficient mice have profoundly low CBG, reduced plasma corticosteroid binding capacity, and heightened mortality during inflammatory stress. These defects are completely rescued by reconstituting CBG, supporting that KLF15 works primarily through CBG to control plasma corticosterone homeostasis. To understand transcriptional mechanisms, we generated the first KLF15 cistromes using newly engineered Klf153xFLAG mice. Unexpectedly, liver KLF15 is predominantly promoter enriched, including Serpina6, where it binds a palindromic GC-rich motif, opens chromatin, and transactivates genes with minimal associated direct gene repression. Overall, we provide critical mechanistic insight into KLF15 function and identify a hepatocyte-intrinsic transcriptional module that potently regulates systemic corticosteroid transport and inflammation.
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Affiliation(s)
- Zhen Jiang
- Amgen Research, South San Francisco, CA 94080, USA
- Gladstone Institutes, San Francisco, CA 94158, USA
| | - Selma Z. Elsarrag
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
- Medical Scientist Training Program and Quantitative and Computational Biosciences Graduate Program, Baylor College of Medicine, Houston, TX 77030, USA
| | - Qiming Duan
- Gladstone Institutes, San Francisco, CA 94158, USA
| | | | - Zhe Wang
- Amgen Research, South San Francisco, CA 94080, USA
| | | | - Sarah McMahon
- Gladstone Institutes, San Francisco, CA 94158, USA
- Biomedical Sciences Graduate Program, UCSF School of Medicine, San Francisco, CA 94143, USA
| | | | | | - Yi Wang
- UCSF Diabetes Center and Department of Medicine, UCSF School of Medicine, San Francisco, CA 94143, USA
| | - Christian Vaisse
- UCSF Diabetes Center and Department of Medicine, UCSF School of Medicine, San Francisco, CA 94143, USA
| | - Jonathan D. Brown
- Division of Cardiovascular Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Mattia Quattrocelli
- Molecular Cardiovascular Biology Division, Heart Institute, Cincinnati Children’s Hospital Medical Center and Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH 45229, USA
| | - Charles Y. Lin
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
- Kronos Bio Inc., Cambridge, MA 02142, USA
| | - Saptarsi M. Haldar
- Amgen Research, South San Francisco, CA 94080, USA
- Gladstone Institutes, San Francisco, CA 94158, USA
- Cardiology Division, Department of Medicine, UCSF School of Medicine, San Francisco, CA 94143, USA
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Tilgar V, Lind M, Lodjak J, Moks K. Corticosterone Response as an Age-Specific Mediator of Nestling Body Mass in a Wild Passerine. Physiol Biochem Zool 2017; 90:512-521. [DOI: 10.1086/692631] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Goutte A, Clément-Chastel C, Moe B, Bech C, Gabrielsen GW, Chastel O. Experimentally reduced corticosterone release promotes early breeding in black-legged kittiwakes. J Exp Biol 2011; 214:2005-13. [DOI: 10.1242/jeb.051979] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
Breeding at the right time is important for successful reproduction. In birds, stressful environmental conditions are known to delay the timing of breeding but the underlying mechanisms are poorly understood. The stress hormone corticosterone appears to be a good candidate for mediating egg-laying date according to early environmental conditions and physiological state. By experimentally reducing the release of corticosterone in black-legged kittiwakes during the pre-laying period, we tested whether egg-laying date was mechanistically linked to corticosterone levels. Male and female kittiwakes were implanted with a low dose of exogenous corticosterone to inhibit endogenous corticosterone production. According to our predictions, the experimental reduction of corticosterone release was paralleled by a significant advancement of egg laying in females (around 4 days earlier). In addition, females with experimentally reduced corticosterone release gained mass during the pre-laying period compared with controls. Ultimately, the advancement of egg laying in females with experimentally reduced corticosterone levels was associated with an enhanced breeding success. This effect was strongly sex specific. In corticosterone-treated male kittiwakes, egg-laying date and reproductive success were not affected, but breeding probability was lower than in controls. This corticosterone treatment did not influence immediate clutch size, or return rate and breeding decision the following year. Our results support the hypothesis that corticosterone secretion during the pre-laying period mediates the timing of breeding in this long-lived seabird, possibly through the dynamics of energy reserves.
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Affiliation(s)
- Aurélie Goutte
- Centre d'Etudes Biologiques de Chizé, CNRS, F-79360, France
| | | | - Børge Moe
- Norwegian Institute for Nature Research (NINA), Arctic Ecology Department, NO-9296 Tromsø, Norway
| | - Claus Bech
- Department of Biology, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim, Norway
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Brummelte S, Schmidt KL, Taves MD, Soma KK, Galea LA. Elevated corticosterone levels in stomach milk, serum, and brain of male and female offspring after maternal corticosterone treatment in the rat. Dev Neurobiol 2010; 70:714-25. [DOI: 10.1002/dneu.20805] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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5
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Ogias D, de Andrade Sá ER, Kasai A, Moisan MP, Alvares EP, Gama P. Fasting differentially regulates plasma corticosterone-binding globulin, glucocorticoid receptor, and cell cycle in the gastric mucosa of pups and adult rats. Am J Physiol Gastrointest Liver Physiol 2010; 298:G117-25. [PMID: 19833863 DOI: 10.1152/ajpgi.00245.2009] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The nutritional status influences gastric growth, and interestingly, whereas cell proliferation is stimulated by fasting in suckling rats, it is inhibited in adult animals. Corticosterone takes part in the mechanisms that govern development, and its effects are regulated in particular by corticosterone-binding globulin (CBG) and glucocorticoid receptor (GR). To investigate whether corticosterone activity responds to fasting and how possible changes might control gastric epithelial cell cycle, we evaluated different parameters during the progression of fasting in 18- and 40-day-old rats. Food restriction induced higher corticosterone plasma concentration at both ages, but only in pups did CBG binding increase after short- and long-term treatments. Fasting also increased gastric GR at transcriptional and protein levels, but the effect was more pronounced in 40-day-old animals. Moreover, in pups, GR was observed in the cytoplasm, whereas, in adults, it accumulated in the nucleus after the onset of fasting. Heat shock protein (HSP) 70 and HSP 90 were differentially regulated and might contribute to the stability of GR and to the high cytoplasmic levels in pups and elevated shuttling in adult rats. As for gastric epithelial cell cycle, whereas cyclin D1 and p21 increased during fasting in pups, in adults, cyclin E slowly decreased, concomitant with higher p27. In summary, we demonstrated that corticosterone function is differentially regulated by fasting in 18- and 40-day-old rats, and such variation might attenuate any possible suppressive effects during postnatal development. We suggest that this mechanism could ultimately increase cell proliferation and allow regular gastric growth during adverse nutritional conditions.
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Affiliation(s)
- Daniela Ogias
- Department of Cell and Developmental Biology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
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6
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Müller C, Almasi B, Roulin A, Breuner CW, Jenni-Eiermann S, Jenni L. Effects of corticosterone pellets on baseline and stress-induced corticosterone and corticosteroid-binding-globulin. Gen Comp Endocrinol 2009; 160:59-66. [PMID: 18996387 DOI: 10.1016/j.ygcen.2008.10.018] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2008] [Revised: 10/02/2008] [Accepted: 10/15/2008] [Indexed: 11/21/2022]
Abstract
Exogenous administration of glucocorticoids is a widely used and efficient tool to investigate the effects of elevated concentrations of these hormones in field studies. Because the effects of corticosterone are dose and duration-dependent, the exact course of plasma corticosterone levels after exogenous administration needs to be known. We tested the performance of self-degradable corticosterone pellets (implanted under the skin) in elevating plasma corticosterone levels. We monitored baseline (sampled within 3min after capture) total corticosterone levels and investigated potential interactions with corticosteroid-binding-globulin (CBG) capacity and the endogenous corticosterone response to handling in Eurasian kestrel Falco tinnunculus and barn owl Tyto alba nestlings. Corticosterone pellets designed for a 7-day-release in rodents elevated circulating baseline total corticosterone during only 2-3 days compared to placebo-nestlings. Highest levels occurred 1-2days after implantation and levels decreased strongly thereafter. CBG capacity was also increased, resulting in a smaller, but still significant, increase in baseline free corticosterone levels. The release of endogenous corticosterone as a response to handling was strong in placebo-nestlings, but absent 2 and 8 days after corticosterone pellet implantation. This indicates a potential shut-down of the hypothalamo-pituitary-adrenal axis after the 2-3 days of elevated baseline corticosterone levels. 20 days after pellet implantation, the endogenous corticosterone response to handling of nestlings implanted with corticosterone pellets attained similar levels as in placebo-nestlings. Self-degradable pellets proved to be an efficient tool to artificially elevate circulating baseline corticosterone especially in field studies, requiring only one intervention. The resulting peak-like elevation of circulating corticosterone, the concomitant elevation of CBG capacity, and the absence of an endogenous corticosterone response to an acute stressor have to be taken into account.
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Affiliation(s)
- Claudia Müller
- Swiss Ornithological Institute, Luzernerstrasse, Sempach, Switzerland.
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Dawson PA, Gardiner B, Lee S, Grimmond S, Markovich D. Kidney transcriptome reveals altered steroid homeostasis in NaS1 sulfate transporter null mice. J Steroid Biochem Mol Biol 2008; 112:55-62. [PMID: 18790054 DOI: 10.1016/j.jsbmb.2008.08.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/11/2008] [Revised: 06/04/2008] [Accepted: 08/18/2008] [Indexed: 10/21/2022]
Abstract
Sulfate is essential for human growth and development, and circulating sulfate levels are maintained by the NaS1 sulfate transporter which is expressed in the kidney. Previously, we generated a NaS1-null (Nas1(-/-)) mouse which exhibits hyposulfatemia. In this study, we investigated the kidney transcriptome of Nas1(-/-) mice. We found increased (n=25) and decreased (n=60) mRNA levels of genes with functional roles that include sulfate transport and steroid metabolism. Corticosteroid-binding globulin was the most up-regulated gene (110% increase) in Nas1(-/-) mouse kidney, whereas the sulfate anion transporter-1 (Sat1) was among the most down-regulated genes (>or=50% decrease). These findings led us to investigate the circulating and urinary steroid levels of Nas1(-/-) and Nas1(+/+) mice, which revealed reduced blood levels of corticosterone ( approximately 50% decrease), dehydroepiandrosterone (DHEA, approximately 30% decrease) and DHEA-sulfate ( approximately 40% decrease), and increased urinary corticosterone ( approximately 16-fold increase) and DHEA ( approximately 40% increase) levels in Nas1(-/-) mice. Our data suggest that NaS1 is essential for maintaining a normal metabolic state in the kidney and that loss of NaS1 function leads to reduced circulating steroid levels and increased urinary steroid excretion.
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Affiliation(s)
- Paul Anthony Dawson
- School of Biomedical Sciences, University of Queensland, St. Lucia, QLD, Australia.
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8
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Adcock RJ, Kattesh HG, Roberts MP, Carroll JA, Saxton AM, Kojima CJ. Temporal relationships between plasma cortisol, corticosteroid-binding globulin (CBG), and the free cortisol index (FCI) in pigs in response to adrenal stimulation or suppression. Stress 2007; 10:305-10. [PMID: 17613944 DOI: 10.1080/10253890701248020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
The objective of this study was to document changes in plasma concentrations of total cortisol, porcine corticosteroid-binding globulin (pCBG), and the free cortisol index (FCI) in pigs over a 6-h period in response to adrenal stimulation or suppression. Twenty-four 8-week old pigs allotted in equal numbers were administered ACTH, dexamethasone or saline, and blood samples were collected every 15 min via an indwelling jugular catheter for 1 h prior to and 5 h following treatment. Total plasma cortisol increased in ACTH-treated pigs and decreased in dexamethasone-treated pigs within 0.25 and 0.5 h, respectively. In contrast, pCBG concentration was altered in an inverse fashion subsequent to the changes exhibited in total cortisol. FCI reflected the changes observed in total cortisol. These results further document the negative relationship that exists between circulating concentrations of plasma cortisol and pCBG, and illustrate that this association exists under conditions of acute stress in the pig.
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Affiliation(s)
- R J Adcock
- Department of Animal Science, The University of Tennessee, Knoxville, TN 37996, USA
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9
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Petersen HH, Andreassen TK, Breiderhoff T, Bräsen JH, Schulz H, Gross V, Gröne HJ, Nykjaer A, Willnow TE. Hyporesponsiveness to glucocorticoids in mice genetically deficient for the corticosteroid binding globulin. Mol Cell Biol 2006; 26:7236-45. [PMID: 16980625 PMCID: PMC1592889 DOI: 10.1128/mcb.00400-06] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Corticosteroid binding globulin (CBG) is the carrier for glucocorticoids in plasma. The protein is believed to keep the steroids inactive and to regulate the amount of free hormone acting on target tissues (free hormone hypothesis). Here, we generated a mouse model genetically deficient for CBG to test the contribution of the carrier to glucocorticoid action and adrenocortical stress response. The absence of CBG resulted in a lack of corticosterone binding activity in serum and in an approximately 10-fold increase in free corticosterone levels in CBG-null mice, consistent with its role in regulation of circulating free hormone levels. Surprisingly, cbg(-/-) animals did not exhibit features seen in organisms with enhanced glucocorticoid signaling. Rather, the mice exhibited increased activity of the pituitary axis of hormonal control, normal levels of gluconeogenetic enzymes, and fatigue, as well as an aggravated response to septic shock, indicating an inability to appropriately respond to the excess free corticosterone in the absence of CBG. Thus, our data suggest an active role for CBG in bioavailability, local delivery, and/or cellular signal transduction of glucocorticoids that extends beyond a function as a mere cargo transporter.
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Affiliation(s)
- Helle Heibroch Petersen
- Max Delbrueck Center for Molecular Medicine, University Medical School, Robert-Roessle-Strasse 10, D-13125 Berlin, Germany
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10
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Deviche P, Breuner C, Orchinik M. Testosterone, corticosterone, and photoperiod interact to regulate plasma levels of binding globulin and free steroid hormone in dark-eyed juncos, Junco hyemalis. Gen Comp Endocrinol 2001; 122:67-77. [PMID: 11352555 DOI: 10.1006/gcen.2001.7613] [Citation(s) in RCA: 113] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The pharmacology and regulation of corticosteroid binding globulins (CBG) in Dark-eyed Juncos, Junco hyemalis, was investigated. The equilibrium dissociation constant for [(3)H]corticosterone (CORT) binding to plasma was <5 nM. This binding site had a similar high affinity for progesterone, approximately fivefold lower affinity for androgens, and negligible affinity for estradiol. The following data suggested that plasma CBG levels are regulated by both testosterone and day length: (1) CBG binding capacity in free-living adult males was greater in early than in late breeding season and greater in males than in females and (2) CBG levels were higher in testosterone-treated, castrated males than in castrated males receiving no testosterone and still higher in testosterone-treated males exposed to long days than in similar males exposed to short days. Birds apparently lack a sex steroid-specific binding globulin, but it was estimated that more than 90% of testosterone in junco plasma should bind to CBG. An increase in plasma CORT, such as occurs during a stress response, was judged to acutely increase free testosterone levels as much as fivefold. Corticosterone and testosterone may thus interact in a complex manner in species that lack sex hormone binding proteins.
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Affiliation(s)
- P Deviche
- Department of Biology, Arizona State University, Tempe, Arizona 85287, USA.
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11
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Roth-Isigkeit AK, Dibbelt L, Schmucker P. Blood levels of corticosteroid-binding globulin, total cortisol and unbound cortisol in patients undergoing coronary artery bypass grafting surgery with cardiopulmonary bypass. Steroids 2000; 65:513-20. [PMID: 10978730 DOI: 10.1016/s0039-128x(00)00133-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Previous studies have demonstrated a persistent rise in serum cortisol concentrations after cardiac surgery. To further investigate this finding and to evaluate the effect of hemodilution that occurs with the onset of cardiopulmonary bypass (CPB), concentrations of cortisol-binding globulin (CBG), total and unbound cortisol, and packed cell volume (PCV) were studied in 28 patients undergoing coronary artery bypass graft surgery. All patients received a standardized general anesthetic using a balanced technique with sufentanil, isoflurane, and midazolam. Blood was collected preoperatively, intraoperatively during CPB, and postoperatively in the evenings on the day of surgery and on the first and second postoperative day. Cortisol and CBG concentrations were measured by radioimmunoassay and were used to calculate the fraction of unbound cortisol. Serum CBG and cortisol concentrations corrected for hemodilution were significantly higher than non-corrected values. Perioperatively, CBG measurements were significantly intercorrelated. Intraoperatively, total and unbound cortisol concentrations were not significantly increased compared to preoperative values. Postoperatively up to the end of the study period serum concentrations of total and unbound cortisol were significantly increased compared to baseline values. Our results suggest that hemodilution occurs in all patients during cardiac surgery and continues up to the second postoperative day. This may lead to an underestimation of serum cortisol and CBG concentrations in patients undergoing heart surgery with CPB. Intraoperatively, concentrations of total and unbound cortisol were not significantly elevated. The postoperative rise in serum total cortisol concentration was accompanied by an increase in unbound cortisol concentration. The postoperative increase of unbound cortisol concentrations in patients undergoing cardiac surgery with CPB was largely due to an increase in cortisol secretion.
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Affiliation(s)
- A K Roth-Isigkeit
- Department of Anesthesia, Medical University of Luebeck, Ratzeburger Allee 160, D-23538, Luebeck, Germany.
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Jeffray TM, Marinoni E, Ramirez MM, Bocking AD, Challis JR. Effect of prenatal betamethasone administration on maternal and fetal corticosteroid-binding globulin concentrations. Am J Obstet Gynecol 1999; 181:1546-51. [PMID: 10601941 DOI: 10.1016/s0002-9378(99)70402-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
OBJECTIVE This study was undertaken to examine the effects of prenatal betamethasone administration on corticosteroid-binding globulin concentrations in maternal and fetal plasma and amniotic fluid. STUDY DESIGN Two groups of patients with preterm labor at 24 to 35 weeks' gestation who were receiving prenatal betamethasone (2 intramuscular doses of 12 mg) were studied. Maternal plasma was obtained before and at variable intervals until 1 week after betamethasone administration. Umbilical cord blood and amniotic fluid samples were collected at the time of delivery. Samples were also collected from patients at risk for preterm delivery who did not receive glucocorticoids. RESULTS Betamethasone suppressed maternal cortisol concentration by >70% within 24 hours of injection but did not significantly alter corticosteroid-binding capacity or relative concentrations of corticosteroid-binding globulin isoforms in either maternal or umbilical cord plasma. Betamethasone reduced corticosteroid-binding capacity in amniotic fluid within 24 hours of injection, and values remained suppressed 1 week after treatment. CONCLUSION Maternal and fetal plasma corticosteroid-binding globulin concentrations were unchanged after maternal betamethasone administration at 24 to 32 weeks' gestation but amniotic fluid corticosteroid-binding globulin concentrations decreased significantly, suggesting different sites of either corticosteroid-binding globulin production or regulation or both.
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Affiliation(s)
- T M Jeffray
- Department of Physiology, University of Toronto, Ontario, Canada
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Cole TJ, Harris HJ, Hoong I, Solomon N, Smith R, Krozowski Z, Fullerton MJ. The glucocorticoid receptor is essential for maintaining basal and dexamethasone-induced repression of the murine corticosteroid-binding globulin gene. Mol Cell Endocrinol 1999; 154:29-36. [PMID: 10509797 DOI: 10.1016/s0303-7207(99)00105-7] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
We have investigated hepatic expression and glucocorticoid regulation of the corticosteroid-binding globulin (CBG) gene in mice lacking a functional glucocorticoid receptor (GR). GR-/- mice show impaired negative feedback in the hypothalamic-pituitary-adrenal axis, resulting in elevated circulating levels of ACTH and corticosterone. This is seen in the neonatal period and continues into adulthood where ACTH and corticosterone levels are increased up to 4-5 fold. Despite high elevation of corticosterone we find no change in mean arterial blood pressure in GR-/- mice and no change in the renal activity of the glucocorticoid-metabolising enzymes 11beta-hydroxysteroid dehydrogenase type-1 (HSD1) and type-2 (HSD2). We do find markedly increased hepatic expression of CBG with a 50% increase in plasma CBG levels. Increased expression of CBG was detected in adult GR-/- mice and also at birth with a greater than 10-fold increase in CBG hepatic mRNA in day-18.5 embryonic GR-/- mice. Adult GR-/- mice were also resistant to dexamethasone-induced repression of CBG expression in the liver. These results indicate that in mice, GR is essential for maintaining the basal level of CBG gene expression in the liver, and is also required for dexamethasone-induced repression of the CBG gene in the adult.
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Affiliation(s)
- T J Cole
- Baker Medical Research Institute, Prahran, Victoria, Australia.
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Zhao XF, Underhill DA, Hammond GL. Hepatic nuclear proteins that bind cis-regulatory elements in the proximal promoter of the rat corticosteroid-binding globulin gene. Mol Cell Endocrinol 1997; 126:203-12. [PMID: 9089658 DOI: 10.1016/s0303-7207(96)03992-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The plasma transport protein for glucocorticoids, corticosteroid-binding globulin (CBG), is produced by hepatocytes, and expression of the CBG gene (Cbg) in the liver is controlled by a variety of hormones, environmental stimuli, and developmental cues. The rat Cbg proximal promoter, including 145 base pairs (bp) from the transcription start site, contains two cis-regulatory elements (designated P1 and P2), and is as transcriptionally active as a much more extended region (approximately 1.2 kbp) of the promoter. We have now characterized the rat liver nuclear proteins that interact with P1 and P2. Several proteins interacted specifically with P1 during an electrophoretic mobility shift assay (EMSA), and based on ultraviolet (UV) cross-linking and Southwestern blot analyses, as well as an antibody-supershifting EMSA, one of these has been identified as hepatic nuclear factor (HNF)1 beta. The major band shift formed with P2 in an EMSA appears to comprise a protein that migrates as a doublet of 58 and 62 KDa on sodium dodecylsulfate-polyacrylamide gel ectrophoresis (SDS-PAGE) after UV cross-linking with an oligonucleotide containing P2, as well as during Southwestern blot analyses. Mutations of the CCAAT sequence within P2 also prevent binding to this protein, the physicochemical properties of which resemble the CCAAT-binding protein CP2. Functional analyses of this region of the rat Cbg proximal promoter fused to a luciferase reporter gene demonstrated that mutations within P1, which prevent its interaction with NHF1, do not influence adversely its transcriptional activity. Thus, although members of the HNF1 family of nuclear proteins play an essential role in the transcriptional activation of several other related genes (e.g., thyroxin-binding globulin and alphal-antitrypsin) in hepatocytes, HNF1 beta does not appear to be required for the basal activity of the rat Cbg promoter. In addition, deletion of P2 from the proximal promoter abolishes transcriptional activity and the CCAAT-binding protein that interacts with P2 probably represents an important determinant of Cbg expression under different physiological conditions.
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Affiliation(s)
- X F Zhao
- Department of Obstetrics and Gynecology, University of Western Ontario, London, Canada
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