The process of second messenger signaling typically begins when an extracellular signaling molecule, such as a hormone or neurotransmitter, binds to a specific receptor on the cell surface. This interaction activates an associated G protein or receptor tyrosine kinase, leading to the production or release of second messengers within the cell. The second messengers then propagate the signal by activating downstream effector proteins, such as kinases or phosphatases, which ultimately bring about the desired cellular response.
