second-messenger-mediated signaling Any intracellular signal transduction in which the signal is passed on within the cell via a second messenger; a small molecule or ion that can be quickly generated or released from intracellular stores, and can diffuse within the cell. Second-messenger signaling includes production or release of the second messenger, and effectors downstream of the second messenger that further transmit the signal within the cell. GO:0019932 biological_process second messenger mediated signaling second messenger mediated signalling second messenger-mediated signaling second messenger-mediated signalling second-messenger-mediated signal transduction second-messenger-mediated signalling