Characteristics
- GPCRs are transmembrane proteins that span the cell membrane and are composed of seven transmembrane (TM) domains, which are connected by intracellular and extracellular loops.
- GPCRs are activated by a wide variety of ligands, including hormones, neurotransmitters, and other signaling molecules. Ligand binding to the extracellular domain of the GPCR causes a conformational change in the receptor that activates the intracellular G protein.
- GPCRs are activated by G proteins, which are heterotrimeric complexes made up of alpha, beta, and gamma subunits. Activation of the G protein leads to the release of the alpha subunit, which then activates an effector enzyme or ion channel.
- GPCRs are regulated by several mechanisms, including receptor desensitization, receptor internalization, and receptor recycling.
- Desensitization refers to the process by which the receptor becomes less responsive to ligand binding after prolonged or excessive activation. Internalization is the process by which the receptor is internalized into the cell and recycled back to the cell surface. This process can either enhance or inhibit signaling, depending on the specific receptor and signaling pathway.
GPCR Signaling Pathway
G protein-coupled receptors (GPCRs) are a type of cell surface receptor that is activated by ligands, such as hormones, neurotransmitters, and other signaling molecules. When activated, GPCRs initiate a signaling cascade through a process called G protein-coupled receptor signaling.