Evolutionary dynamics of metazoan TRP channels.

Transient receptor potential (TRP) channels are unusual among cation channels because of their diverse cation selectivities and activation mechanisms. TRP channels thus play major roles in various sensory perceptions by functioning as multimodal signal integrators. Some TRP subfamily members are also implicated in acute and chronic pain and inflammation. So far, most TRP channel studies have been targeted to human and model organisms within a limited evolutionary context. Classification of TRP channels in various animal genomes has revealed extensive gene gain and loss events across animal species. Furthermore, the chemical activation profiles of some orthologous TRP channels were different between species such as human and mouse. Amino acid substitutions must underlie such differences, and the crucial amino acid residues have been identified in some cases. These changes represent the evolution of TRP channels at the amino acid sequence level. There is also evidence that TRP channels have obtained species-diversity through alternative splicing and possibly cis-regulatory element mutations. All of the above demonstrate the dynamic and plastic evolutionary history of metazoan TRP channels at multiple levels, possibly in conjunction with the specific habitats and life histories of individual species.