TRPMLs, also termed mucolipins, are members of the TRP channels. In mammals, three TRPMLs are known to date (TRPML1-3 or MCOLN1-3). They are all localized to endolysosomes, although when over expressed in heterologous systems, TRPML3 is found on the plasma membrane. These channels are Ca2+ permeable and display inward rectifying current properties. Like all members of this family, TRPMLs have six transmembrane domains and intracellular N- and C-termini (relatively short tails compared to other members). They are characterized by an exceptionally large extracellular (luminal) loop between transmembrane domains 1 and 2, and N-glycosylation sites are present in the first extracellular (luminal) loop.n In mammals, TRPML1 is expressed in a ubiquitous manner and shows highest expression in the brain, kidney, spleen, liver and heart. TRPML2 and TRPML3 are less widely expressed. Interestingly, in mouse, two splice variants exist for TRPML2. The shorter variant is more broadly expressed and is dominant over the longer variant in the thymus, spleen and kidney. TRPML3 is highly detected in the thymus, lung, kidney, spleen and eye, some epithelial cellsand brain.