ABSTRACT

Mechanically activating (MA) channels transduce numerous physiological functions. Tentonin 3/TMEM150C (TTN3) confers MA currents with slow-inactivation kinetics in somato- and baro-sensory neurons. Despite the distinct currents when heterologously expressed, whether TTN3 forms a channel pore is unknown. Here we demonstrate that purified TTN3 proteins incorporated into the lipid bilayer exhibited spontaneous and pressure-sensitive channel currents. MA currents of TTN3 with unique slow-inactivation kinetics were conserved throughout the vertebrate phyla. The activation threshold of TTN3 and its pharmacological perturbations separated TTN3 from Piezo1. Deep neural network structure prediction programmes coupled with mutagenetic analysis predicted a rectangular shaped tetrameric structure with six transmembrane helices and a pore at the inter-subunit centre. The putative pore aligned with two helices of each subunit and had constriction sites whose mutations changed the MA currents. These results suggest that TTN3 is a pore-forming subunit of a slow-inactivation MA channel, possibly with a unique structure.