TRP channels in oxygen physiology: distinctive functional properties and roles of TRPA1 in O(2) sensing

Transient Receptor Potential (TRP) proteins form cation channels characterized by a wide variety of activation triggers. Here, we overview a group of TRP channels that respond to reactive redox species to transduce physiological signals, with a focus on TRPA1 and its role in oxygen physiology. Our systematic evaluation of oxidation sensitivity using cysteine-selective reactive disulphides with different redox potentials reveals that TRPA1 has the highest sensitivity to oxidants/electrophiles among the TRP channels, which enables it to sense O(2). Proline hydroxylation by O(2)-dependent hydroxylases also regulates the O(2)-sensing function by inhibiting TRPA1 in normoxia; TRPA1 is activated by hypoxia through relief from the inhibition and by hyperoxia through cysteine oxidation that overrides the inhibition. TRPA1 enhances neuronal discharges induced by hyperoxia and hypoxia in the vagus to underlie respiratory adaptation to changes in O(2) availability. This importance of TRPA1 in non-carotid body O(2) sensors can be extended to the universal significance of redox-sensitive TRP channels in O(2) adaptation.