Multiple mechanisms of receptor-G protein signaling specificity.

The hormone-receptor-G protein complex transduces extracellular information into intracellular signals that ultimately regulate cellular functions in a highly specific manner. There are hundreds of receptor types that transduce signals through a relatively limited repertoire of heterotrimeric G proteins. Linear models of signaling specificity that require specific and highly selective coupling of hormone to receptor to G protein have proven inadequate to explain how highly particular signals are funneled through the G protein "bottleneck." Recent studies have uncovered a plethora of mechanisms that contribute to signaling specificity. This review focuses on the mechanisms that contribute to specificity in the interactions of receptors with G proteins.