Specificity of receptor-G protein coupling: Protein structure and cellular determinants

G protein-coupled receptors are involved In a tremendous range of signaling processes in the nervous system. The outlines of a molecular basis for specificity of receptor-G protein coupling has been established, but important details remain unclear. The second and third intracellular loops of most G protein-coupled receptors and the carboxyl terminus of the G protein alpha subunit have the most clearly established roles in specificity of coupling. The role of other regions of receptor and G protein, especially the G beta gamma subunit, is an area needing more investigation. A discrepancy between specificity observed in vitro and in intact cells suggests a role for targeting and compartmentation of signaling components to account for the striking specificity observed in intact cells. The role of caveolin and PDZ domain-containing proteins will be of significant interest. (C) 1998 Academic Press.