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Nucleic Acids Res. 1995 Feb 11;23(3):327-33.

Transcriptional activation of the nuclear receptor RZR alpha by the pineal gland hormone melatonin and identification of CGP 52608 as a synthetic ligand.

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  • 1Pharma-Forschung, Ciba-Geigy AG, Basel, Switzerland.


Many important physiological functions are controlled by hormones via binding and activating members of the nuclear receptor superfamily. This group of structurally related transcription factors also includes a still growing number of orphan receptors for which no ligand is known so far. The identification of ligands for orphan receptors is a key to understanding their physiological role, as has been successfully shown for retinoid X receptors and the discovery of 9-cis retinoic acid as a specific ligand. We have discovered very recently that the pineal gland hormone melatonin is a specific ligand for the brain-specific nuclear receptor RZR beta. Here we report that the alpha-subtype of RZR, RZR alpha and its splicing variant ROR alpha 1, is also a nuclear receptor for melatonin with binding specificities in the low nanomolar range. In contrast to RZR beta, RZR/ROR alpha is expressed in many tissues and cells outside the brain. We found that RZR alpha and ROR alpha 1 vary in their constitutive transactivational activity and are activated to a different extent by melatonin. Furthermore, we identified a synthetic RZR-ligand, the thiazolidine dione CGP 52608. This compound is a functional analogue of melatonin at its nuclear receptor, but does not bind to the high affinity membrane receptor for melatonin. Therefore, this specific RZR-ligand may help to differentiate between nuclear and membrane signalling of melatonin.

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