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Nature. 1998 Oct 8;395(6702):612-5.

Androstane metabolites bind to and deactivate the nuclear receptor CAR-beta.

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The City of Hope National Medical Center, Duarte, California 91010, USA.


The orphan receptor CAR-beta binds DNA as a heterodimer with the retinoid-X receptor and activates gene transcription in a constitutive manner. Here we show that, in contrast to the classical nuclear receptors, the constitutive activity of CAR-beta results from a ligand-independent recruitment of transcriptional co-activators. While searching for potential ligands of CAR-beta, we found that the steroids androstanol and androstenol inhibit the constitutive activity of CAR-beta. This effect is stereospecific: only 3alpha-hydroxy, 5alpha-reduced androstanes are active. These androstanes do not interfere with heterodimerization or DNA binding of CAR-beta; instead, they promote co-activator release from the ligand-binding domain. These androstane ligands are examples of naturally occurring inverse agonists that reverse transcriptional activation by nuclear receptors. CAR-beta (constitutive androstane receptor-beta), therefore, defines an unanticipated steroidal signalling pathway that functions in a manner opposite to that of the conventional nuclear receptor pathways.

[Indexed for MEDLINE]

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