TRPM

TRPM is a family of transient receptor potential ion channels where the "M" stands for "melastatin". Functional TRPM channels are believed to be tetramers.

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 &alpha;-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.
 * TRPM4/5 are impermeable to calcium.
 * TRPM3/6/7 are highly permeable to both calcium and magnesium.

The mechanism of activation also varies greatly among TRPM channels.
 * TRP2 is activated by Adenosine diphosphate ribose and heat.
 * TRPM2 is a sensor of redox status in cells.
 * TRPM4/5 are activated by intracellular calcium and heat.
 * TRPM8, conversely, can be activated by low temperatures, menthol, eucalyptol and icilin.

Functions
Among the functional responsibilities of the TRPM channels are:
 * sensory transduction in taste cells (TRPM5).
 * regulation of magnesium reabsorption in the kidneys and absorption in the intestines (TRPM6).