D. G. Greenhalgh1,2, K. Cho1,2, T. Green1, S. Leventhal1, D. Lim1, D. Greenhalgh1,2 1Shriners Hospitals For Children Northern California,Burns,Sacramento, CA, USA 2University Of California – Davis,Burns,Sacramento, CA, USA
Introduction: We have previously reported that a 118 amino acid fragment of the N-terminus of GR [hGR-S1(-349A)] which lacks ligand and DNA binding domains has a markedly enhanced response to steroids compared to the full-length GR (hGRa) alone. How hGR-S1(-349A) enhances glucocorticoid activity is not known. We sought to determine whether blocking classical glucocorticoid receptor pathway with RU486 would alter the enhanced activity of the altered hGR-S1(-349A). Since the fragment lacked both DNA and ligand binding domains we hypothesized that RU486 would not alter its activity.
Methods: Both the hGR and hGR-S1(-349A) were cloned into tsA201 cells and tested for glucocorticoid activity at various doses of hydrocortisone using our standard luciferase assay.
Results: hGR-S1(-349A) had the typical augmentation in response to increasing doses of hydrocortisone. To our surprise, RU486 inhibited the activity of hGR-S1(-349A) suggesting a role for the hGR in its activity (figure).
Conclusion: hGR-S1(-349A) hyperactivity is inhibited by RU486 despite lacking DNA and ligand binding demands. These findings suggest that hGR-S1(-349A) acts as a cofactor in conjunction with hGR to augment the glucocorticoid stress response.
