Sensitivity of Takifugu TRPA1 to thermal stimulations analyzed in oocytes expression system

Transient receptor potential ankyrin 1 (TRPA1s) from insects and several tetrapod vertebrates except rodents have been reported to be activated by high temperature with a relatively clear threshold. Our previous report, however, indicated that oocytes expressing zebrafish TRPA1b showed cold and heat-induced responses. Further, we also observed that zebrafish TRPA1b was gradually heat activated without a clear threshold. To study the possibility that these unique properties of thermal sensing of zebrafish TRPA1b are common to TRPA1s from other fish, we focused on the thermal response of pufferfish transient receptor potential ankyrin 1 (pfTRPA1) in the present study. By the two-electrode voltage clamp method using the Xenopus oocyte expression system, ionic currents were analyzed. Although some batches of pfTRPA1-expressing oocytes responded only to cold or heat stimulation, dual sensitivity to both cold and heat stimuli associated with pfTRPA1 expression was repeatedly observed. We detected a rapid response of oocytes expressing pfTRPA1 below 10°C and also a gradual activation above 25°C without an apparent threshold. The results indicated that these thermal sensitivities of fish TRPA1 are clearly different from those of TRPA1s of tetrapod vertebrates.