Molecular determinants of hormone sensitivity in rainbow trout glucocorticoid receptors 1 and 2

• Published in: Molecular and cellular endocrinology 2011-02, Vol.333 (2), p.181-189
• Main Authors: Sturm, Armin, Colliar, Louise, Leaver, Michael J., Bury, Nic R.
• Format: Article
• Language: English
• Subjects: Activation function 2; Amino Acid Sequence; Animals; Biochemistry, Molecular Biology; Cercopithecus aethiops; chimerism; Cortisol; COS Cells; Determinants; dexamethasone; Dexamethasone - pharmacology; Fish; glucocorticoid receptors; Glucocorticoids; Hormones; Hydrocortisone - pharmacology; Life Sciences; Ligand binding domain; Molecular Sequence Data; Mutant Proteins - chemistry; Mutant Proteins - genetics; Mutant Proteins - metabolism; mutants; Oncorhynchus mykiss; Oncorhynchus mykiss - genetics; Protein Structure, Tertiary; Receptors; Receptors, Glucocorticoid - chemistry; Receptors, Glucocorticoid - genetics; Receptors, Glucocorticoid - metabolism; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; Salmonidae; Salmonids; Sequence Alignment; Sequence Homology, Amino Acid; Steroid receptors; Stress response; Teleost Fish; Teleostei; transcriptional activation; Transcriptional Activation - drug effects; Transcriptional Activation - genetics; Trout
• ISSN: 0303-7207; 1872-8057; 0303-7207
• DOI: 10.1016/j.mce.2010.12.033

Many teleost fish possess two glucocorticoid receptors (GR). In the rainbow trout rtGR1 and rtGR2 differ in their affinities to dexamethasone and EC50 values for glucocorticoids in transactivation assays, with rtGR2 being more sensitive. The objective of this study was to identify the molecular traits underlying the sensitivity difference. Domain-swap mutants between rtGR1 and rtGR2 showed that sensitivity was mainly determined by the hormone binding domain (E-domain). Chimeras exchanging three E-domain subregions indicated that all subregions influenced sensitivity, with the most C-terminal region that included AF2 having the greatest (12.6-fold) effects on cortisol transactivation EC50. The C-terminal extremity (CTE) in rtGR1 departs from a consensus preserved in other GRs. Introducing the consensus CTE into rtGR1 provoked a 4.2-fold decrease in transactivation EC50, suggesting CTE is one of several determinants of rtGR1's hyposensitivity. GRs with similar unusual CTEs exist in other salmonids, suggesting hyposensitive GR have evolved in this highly successful teleost lineage.