New insights into activation of the steroid hormone receptor superfamily.

For many years the prevailing view of how steroid hormone receptors exert their effects on gene transcription has been that these intracellular receptor proteins, upon association with their specific cognate ligands, undergo a transformation to a state where they are capable of interacting with chromatin and regulating the transcription of specific genes. It has become implicit dogma in the field of biochemical endocrinology that receptor activation is absolutely dependent upon this ligand-binding event. However, recent studies described here by Bert O'Malley and colleagues have shown that certain members of the steroid hormone receptor superfamily can be activated in a totally ligand-independent manner by a cell membrane receptor agonist, the neurotransmitter dopamine.