G-Protein Coupled Receptor (GPCR) signaling involves extracellular signals that trigger a cascade of intracellular responses via a series of membrane-bound receptors. Key to the regulation of the GPCR signaling cascade is the involvement of cyclic AMP (cAMP) and cyclic GMP (cGMP). One of the key functions of both molecules is to activate Guanine Exchange Factors (GEF), which in turn play a role in the activation of G proteins.