Regulation of receptor expression by agonists: transcriptional and post-transcriptional controls

The molecular cloning of certain members of several distinct classes of receptors has opened up new avenues by which the regulation of signal-transducing proteins can be investigated. The information derived from molecular cloning permits not only studies of functional domains via mutagenesis, but also the study of gene regulation and the cell biology of these receptors by the use of molecular probes. All receptors are bifunctional, possessing domains for ligand binding as well as for signal propagation through binding to other protein(s), DNA or ion channels. Regulation of receptor expression and function in response to agonist stimulation is a central feature of receptor biology. In this article, Drs Hadcock and Malbon focus on the regulation of receptor expression by agonists at the transcriptional and post-transcriptional levels. Regulation of the expression of three classes of receptors central to neurobiology is highlighted: namely, steroid hormone receptors (estrogen receptor), G protein-coupled receptors (beta2-adrenergic receptor) and tyrosine kinase receptors (epidermal growth factor receptor). The emerging idea of cross regulation between receptors is also discussed in order to demonstrate the complexities of studying receptor expression.