Recombinant receptors as probes for the study of genetic stability

Membrane receptors coupled to GTP binding G-proteins constitute one of the largest families of proteins involved in ligand binding, signal transmission and modulation of physiological effects. A large majority of current pharmaceuticals are actually ligands for this type of receptor, including e.g. the catecholamine, dopamine, serotonin and histamine antagonists. In recent years, an impressive number of the genes encoding these receptors have been cloned, sequenced and expressed in model cell lines. Molecular genetics has thus uncovered the existence of a surprisingly large number of homologous receptor subtypes each capable of binding the same natural ligand, but which may be distinguished on the basis of variable recognition patterns of synthetic ligand panels, variable expression during development and differentiation or different G-protein coupling and effector modulation. We have summarized in Table 1 some of the recently cloned receptors and have attempted to group them according to the type of ligand recognized: non peptidic, peptidic or other, including light and olfactory substances. Further information and references can be found in recent reviews.