Details

Autor(en) / Beteiligte

• Gupta, B. B. P.
• Lalchhandama, K.

Titel

Molecular mechanisms of glucocorticoid action

Ist Teil von

• Current science (Bangalore), 2002-11, Vol.83 (9), p.1103-1111

Ort / Verlag

Current Science Association

Erscheinungsjahr

2002

Quelle

Elektronische Zeitschriftenbibliothek (Open access)

Beschreibungen/Notizen

• Glucocorticoids act on target cells via two isoforms of intracellular glucocorticoid receptors (GRs) called GRα (hormone-binding form) and GRβ which does not bind any glucocorticoids. A cycle of Hsp90 chaperone and co-chaperones maintains the functional status of GRs and their recycling. The binding of a glucocorticoid hormone to GRα leads to its activation and translocation from the cytoplasm to nucleus. Glucocorticoids influence activities of genes of target cells using two different types of mechanism. In type-1 mechanism, the hormone-bound GRα undergoes homodimerization (GRα/GRα) or heterodimerization (GRα/ GRβ). A homodimer binds directly to a glucocorticoid response element (GRE) and activates gene transcription. Binding of a heterodimer (GRα/GRβ) to GRE induces only partial transactivation, because GRβ inhibits the hormone-induced, GRα-mediated stimulation of gene expression by specifically inhibiting GRE-mediated transcription. In some cases, a hormone– GRα complex binds to a negative GRE (nGRE) and suppresses transcription (transrepression). In type-2 mechanism, a hormone–GRα complex binds to other transcription factors (TFs) and inhibits the transcription of target genes stimulated by the TFs. GRα-induced transactivation and transrepression of genes may also involve several transcription co-activators and dominant negative inhibitors respectively. The present article provides critical information on structure and types of GRs, GR gene, chaperone cycle, and details of different types of mechanism of glucocorticoid actions.