Discovery of glucocorticoid receptor-beta in mice with a role in metabolism.
Glucocorticoid hormones control diverse physiological processes, including metabolism and immunity, by activating the major glucocorticoid receptor (GR) isoform, GRalpha. However, humans express an alternative isoform, human (h)GRbeta, that acts as an inhibitor of hGRalpha to produce a state of glucocorticoid resistance. Indeed, evidence exists that hGRbeta contributes to many diseases and resistance to glucocorticoid hormone therapy. However, rigorous testing of the GRbeta contribution has not been possible, because rodents, especially mice, are not thought to express the beta-isoform. Here, we report expression of GRbeta mRNA and protein in the mouse. The mGRbeta isoform arises from a distinct alternative splicing mechanism utilizing intron 8, rather than exon 9 as in humans. The splicing event produces a form of beta that is similar in structure and functionality to hGRbeta. Mouse (m)GRbeta has a degenerate C-terminal region that is the same size as hGRbeta. Using a variety of newly developed tools, such as a mGRbeta-specific antibody and constructs for overexpression and short hairpin RNA knockdown, we demonstrate that mGRbeta cannot bind dexamethasone agonist, is inhibitory of mGRalpha, and is up-regulated by inflammatory signals. These properties are the same as reported for hGRbeta. Additionally, novel data is presented that mGRbeta is involved in metabolism. When murine tissue culture cells are treated with insulin, no effect on mGRalpha expression was observed, but GRbeta was elevated. In mice subjected to fasting-refeeding, a large increase of GRbeta was seen in the liver, whereas mGRalpha was unchanged. This work uncovers the much-needed rodent model of GRbeta for investigations of physiology and disease.
Hinds
Terry D
TD
Department of Physiology and Pharmacology, University of Toledo College of Medicine, 3035 Arlington Avenue, Toledo, OH 43614-5804, USA.
Ramakrishnan
Sadeesh
S
Cash
Harrison A
HA
Stechschulte
Lance A
LA
Heinrich
Garrett
G
Najjar
Sonia M
SM
Sanchez
Edwin R
ER
D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D019556:COS Cells; D002522:Chlorocebus aethiops; D003001:Cloning, Molecular; D004032:Diet; D005455:Fluorescent Antibody Technique; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000187:drug effects; D020868:Gene Silencing / Q000187:drug effects; D005799:Genes, Dominant / Q000235:genetics; D005938:Glucocorticoids / Q000494:pharmacology; D007438:Introns / Q000235:genetics; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011965:Receptors, Glucocorticoid / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*
D005938:Glucocorticoids; D020033:Protein Isoforms; D012333:RNA, Messenger; D011965:Receptors, Glucocorticoid; C411470:glucocorticoid receptor alpha; C121943:glucocorticoid receptor beta