Abstract
TRPM8 was cloned as the family of thermally activated TRP channels. TRPM8 is cooling activated channel involved in cold sensation. However, it is unclear which amino acid residues are critical for ion permeation as the pore. We hypothesized that the pore is made by three consecutive hydrophobic amino acid residues between TM5 and TM6, highly conserved among different species or related TRP channels. WIF (898-900) were residues consistent with above hypothesis. We examined the involvement of this region on ion permeation by constructing TRPM8 mutant WIF898AAA, in which corresponding amino acid residues were replaced by alanine. Ion permeation was investigated with Fura-2 calcium imaging method. Menthol or cooling (from 30 °C to 15 °C) elevated intracellular calcium ion concentration in wild type TRPM8 -expressing cells but not in WIF898AAA -expressing cells. We conclude that the conserved three consecutive hydrophobic amino acid residues between TM5 and TM6 (WIF) are critical for ion permeation of TRPM8. [J Physiol Sci. 2006;56 Suppl:S153]
