Changes in signal transduction pathways

Mutations within genes coding for G protein-coupled receptors (GPCRs) can lead to one of two major outcomes—a loss-of-function or a gain-of-function. Loss-of-function mutations prevent signaling in GPCR pathways, even in the presence of signaling molecules. Gain-of-function mutations activate signaling in GPCR pathways, even in the absence of signaling molecules.