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.
- TRPM4/5 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.
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).
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