Oxygen is an essential gasotransmitter directly sensed via protein gasoreceptors

The current restrictive criteria for gasotransmitters exclude oxygen(O_(2))as a gasotransmitter in vertebrates.In this manuscript,I propose a revision of gasotransmitter criteria to include O_(2) per se as a signaling molecule and'essential gasotransmitter'for vertebrates.This revision would enable us to search for protein-based O_(2)-binding sensors(gasoreceptors)in all cells in the brain or other tissues rather than specialized tissues such as the carotid body or gills.If microorganisms have protein-based O_(2)-binding sensors or gasoreceptors such as DosP or FixL or FNR with diverse signaling domains,then eukaryotic cells must also have O_(2)-binding sensors or gasoreceptors.Just as there are proteinbased receptor(s)for nitric oxide(GUCY1A,GUCY1B,CLOCK,NR1D2)in cells of diverse tissues,it is reasonable to consider that there are protein-based receptors for O_(2) in cells of diverse tissues as well.In mammals,O_(2) must be acting as a gasotransmitter or gaseous signaling molecule via protein-based gasoreceptors such as androglobin that very likely mediate acute sensing of O_(2).Accepting O_(2) as an essential gasotransmitter will enable us to search for gasoreceptors not only for O_(2) but also for other nonessential gasotransmitters such as hydrogen sulfide,ammonia,methane,and ethylene.It will also allow us to investigate the role of environment-derived metal ions in acute gas(or solute)sensing within and between organisms.Finally,accepting O_(2) per se as a signaling molecule acting via gasoreceptors will open up the field of gasocrinology.