TRPM

TRPM is a family of transient receptor potential ion channels (the "M" stands for "melastatin"). Functional TRPM channels are believed to form tetramers. The TRPM family consists of eight different channels, TRPM1–TRPM8.

Unlike the TRPC and TRPV sub-families, TRPM subunits do not contain N-terminal ankyrin repeat motifs but, rather, contain entire functional proteins in their C-termini. TRPM6 and TRPM7, for example, contain functional α-kinase segments, which are a type of serine/threonine-specific protein kinase.

Permeability and activation

The relative permeability of calcium and magnesium varies widely among TRPM channels.

The mechanism of activation also varies greatly among TRPM channels.

TRPM5

Transient receptor potential cation channel subfamily M member 5 (TRPM5), also known as long transient receptor potential channel 5 is a protein that in humans is encoded by the TRPM5 gene.

Function

TRPM5 is a key component of taste transduction in the gustatory system of bitter, sweet and umami tastes being activated by high levels of intracellular calcium. It has also been targeted as a possible contributor to fat taste signaling. The calcium dependent opening of TRPM5 produces a depolarizing generator potential which leads to an action potential.

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This article incorporates text from the United States National Library of Medicine, which is in the public domain.

TRPM8

Transient receptor potential cation channel subfamily M 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.

Structure

The TRPM8 channel is a homotetramer, composed of four identical subunits with a transmembrane domain with six helices (S1-S6). The first four, S1-S4, 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 responding to result in ion flow to cold and menthol stimuli.

Function

TRPM8 is an ion channel, upon activation it allows the entry of Na⁺ (sodium) and Ca²⁺ (calcium) ions to the cell that 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.