Transient receptor potential cation channel subfamily M (melastatin) member 8 (TRPM8), also known as the cold and menthol receptor 1 (CMR1), is a protein that in humans is encoded by the TRPM8 gene. The TRPM8 channel is the primary molecular transducer of cold somatosensation in humans. In addition, mints can desensitize a region through the activation of TRPM8 receptors (the 'cold'/menthol receptor). Structure The TRPM8 channel is a homotetramer, composed of four identical subunits with a transmembrane domain with six helices (S1–6). The first four, S1–4, act as the voltage sensor and allow binding of menthol, icilin and similar channel agonists. S5 and S6 and a connecting loop, also part of the structure, make up the pore, a non-selective cation channel which consists of a highly conserved hydrophobic region. A range of diverse components are required for the high level of specificity in response to cold and menthol stimuli which eventually lead to ion flow through the protein channel. Function TRPM8 is an ion channel: upon activation, it allows the entry of Na+ and Ca2+ ions into the cell, which leads to depolarization and the generation of an action potential. The signal is conducted from primary afferents (type C- and A-delta) eventually leading to the sensation of cold and cold pain. The TRPM8 protein is expressed in sensory neurons, and it is activated by cold temperatures and cooling agents, such as menthol and icilin whereas WS-12 and CPS-369 are the most selective agonists of TRPM8. TRPM8 is also expressed in the prostate, lungs, and bladder where its function is not well understood. Role in the nervous system The transient receptor potential channel (TRP) superfamily, which includes the menthol (TRPM8) and capsaicin receptors (TRPV1), serve a variety of functions in the peripheral and central nervous systems. In the peripheral nervous system, TRPs respond to stimuli from temperature, pressure, inflammatory agents, and receptor activation. Central nervous system roles of the receptors include neurite outgrowth, receptor signaling, and excitotoxic cell death resulting from noxious stimuli. McKemy et al., 2002 provided some of the first evidence for existence of a cold-activated receptor throughout the mammalian somatosensory system. Using calcium imaging and patch clamp based approaches, they showed a response in dorsal root ganglion (DRG) neurons that exposure to cold, 20 °C or cooler, lead to a response in calcium influx. This receptor was shown to respond to both cold temperatures, menthol, and similar now-known