A G protein-coupled receptor (GPCR) is a type of protein that sits on the surface of a cell and detects signals from outside the cell. When a signal molecule, called a ligand, binds to a GPCR, it triggers a chain of events inside the cell that leads to a change in cell behavior.
GPCRs are the largest family of membrane proteins in the human body, and they are involved in a wide range of cellular processes, including vision, smell, taste, hearing, hormone signaling, and neurotransmission.
Here is a simple analogy to help you understand how GPCRs work:
Imagine a GPCR as a doorbell. When someone rings the doorbell (ligand binding), it sends a signal inside the house (cell). This signal triggers a bell to ring (G protein activation), which then alerts the people inside the house (effector proteins) to take action (change in cell behavior).
GPCRs are essential for many of the body’s most important functions. For example, GPCRs in the eye allow us to see, and GPCRs in the nose allow us to smell. GPCRs are also involved in regulating blood pressure, heart rate, and hormone levels.