Human TRPA1 is an inherently mechanosensitive bilayer-gated ion channel
The Transient Receptor Potential Ankyrin 1 (TRPA1) channel is an intrinsic chemo- and thermo-sensitive ion channel with distinct sensory signaling properties. Although a role of TRPA1 in mammalian mechanosensory transduction in vivo seems likely, it remains to be shown that TRPA1 has the inherent capability to respond to mechanical stimuli. Here we have used the patch-clamp technique to study the response of human purified TRPA1 (hTRPA1), reconstituted into artificial lipid bilayers, to changes in bilayer pressure. We report that hTRPA1 responded with increased single-channel open probability (Po) within the applied pressure interval of 7.5 to 60 mmHg with a half maximum Po (P50) value of 38.0 {+/-} 2.3 mmHg. The Po value reached a maximum close to 1 (0.87 {+/-} 0.02) at 60 mmHg. Within the same pressure interval, hTRPA1 without its N-terminal ankyrin repeat domain ({Delta}1-688 hTRPA1) responded fully opened (0.99 {+/-} 0.01) at 60 mmHg and with a P50 value of 39.0 {+/-} 1.1 mmHg. The pressure-evoked responses of hTRPA1 and {Delta}1-688 hTRPA1 at 45 mmHg were inhibited by the TRPA1 antagonist HC030031, and the activity of purified hTRPA1 at 45 mmHg was abolished by the thiol reducing agent tris(2-carboxyethyl)phosphine (TCEP). In conclusion, hTRPA1 is an inherent mechanosensitive ion channel gated by force-from-lipids. The hTRPA1 mechanosensitivity is dependent on the redox environment, and it is suggested that oxidative stress shifts hTRPA1 into a protein conformation sensitive to mechanical stimuli.