What is the process of GPCR ligand binding?

When a ligand attaches to a GPCR, it causes a structural change within the receptor’s seven transmembrane regions. This change induces the activation of the receptors C-terminus, which then brings in another substance to activate the associated G protein. This interaction initiates the swapping of GTP for GDP, resulting in a split G-protein into two parts: an alpha subunit and beta-gamma subunits. These subunits then carry and transmit signals downstream to initiate various cellular responses. When separated, both the alpha (α) and beta-gamma (βγ) subunits of the G protein influence the functions of effector molecules that directly generate cellular responses. GPCRs also have the ability to trigger different signaling pathways by interacting with arrestins. These interactions can lead to the activation of alternative signaling pathways that are independent of G proteins. Arrestins can act as scaffolds to recruit various signaling proteins, leading to diverse cellular responses such as receptor desensitization and internalization.