The mammalian melastatin-related transient receptor potential (TRPM) is a subfamily of the TRP family. The family was named after the first discovered member, melastatin (TRPM1) whose gene was identified in metastatic and benign melanomas^1-3. 

The TRPM family consists of eight members designated as TRPM1-8 that can be further divided into four pairs: TRPM1 and TRPM3; TRPM2 and TRPM8; TRPM4 and TRPM5; and TRPM6 and TRPM7^1,2.

The TRPM proteins share structural homology with other members of the TRP superfamily channels; six putative transmembrane domains, and cytoplasmic N- and C-termini. However, due to their long N- and C-termini they are also named the long TRP channel family^1-3. 

TRPM4 and TRPM5 are the only TRP channels that are permeable to monovalent cations but not to Ca²⁺. TRPM4 is expressed as at least two alternative spliced isoforms, TRPM4a and TRPM4b which consist of shorter and longer N-terminal regions, respectively. TRPM4a displays little activity, TRPM4b and TRPM5 appear to be directly activated by an increase in intracellular Ca²⁺ concentration^4,5.

TRPM5 is primarily expressed in taste buds and also in stomach, small intestine, uterus and testes². Regulation of TRPM5 by G-protein-coupled receptors and PLC-mediated IP3 production has been substantiated by the colocalization of TRPM5, of a taste-cell-specific PLC isoform and of receptors for sweet, bitter and amino acid (umami) tastes in taste tissue. It has furthermore been shown that desensitization of TRPM5 following receptor stimulation can be reversed by phosphatidylinositol (4,5)-bisphosphate (PIP2), the substrate of PLC².