TRPM

TRPM is a family of transient receptor potential ion channels (M standing for wikt:melastatin).^[1] Functional TRPM channels are believed to form tetramers.^[2] The TRPM family consists of eight different channels, TRPM1–TRPM8.^[3]

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.

• TRPM4 and TRPM5 are impermeable to calcium.
• TRPM3, TRPM6 and TRPM7 are highly permeable to both calcium and magnesium.

The mechanism of activation also varies greatly among TRPM channels.

• TRPM2 is activated by ADP-ribose adenosine 5'-diphosphoribose and functions as a sensor of redox status in cells.^[4]
• TRPM4 and TRPM5 are activated by intracellular calcium.
• TRPM8 can be activated by low temperatures, menthol, eucalyptol and icilin.^[5][6]

Functions

Among the functional responsibilities of the TRPM channels are:

• regulation of calcium oscillations after T cell activation^[7] and prevention of cardiac conduction disorders (TRPM4).^[8]
• modulation of insulin secretion and sensory transduction in taste cells (TRPM5).^[9]
• cold sensation (TRPM8).
• heat sensation and inflammatory pain (TRPM3).^[10]
• regulation of magnesium reabsorption in the kidneys and absorption in the intestines (TRPM6).^[11]
• regulation of cell adhesion (TRPM7).^[12]

Genes

• TRPM1, TRPM2, TRPM3, TRPM4, TRPM5, TRPM6, TRPM7, TRPM8