Structure of the Full-Length TRPV2 Channel by cryoEM

Abstract

Transient receptor potential (TRP) proteins form a superfamily of cation channels that predominantly regulate the flux of Ca2+ ions across membranes in both excitable and non-excitable cells. While many TRP channels respond to a wide variety of chemical and physical stimuli, several TRP channels exhibit constitutive activity. A recent structural analysis of a “minimal subunit” TRPV1 construct, a prototypical ligand-activated TRP channel, elucidated a mechanism of channel activation by agonists through the dynamic nature of the outer pore region of the channel. Though homologous to TRPV1, TRPV2 shows constitutive activity in the absence of ligand; however the mechanism underlying this activity is elusive due to lack of high-resolution structures. To further understand the critical role of the outer pore region in activity of TRP channels, we have determined the structure of full-length TRPV2 at ∼4Å resolution by direct-electron counting cryo electron microscopy (cryoEM). The structure of TRPV2 revealed that this constitutively active TRP channel features a wide flexible outer pore region in the absence of activator. The geometry of this region differs from that observed in “minimal subunit” TRPV1 and is likely favored by the presence of the turret domain in the full-length TRPV2 protein used for structure determination. In contrast, the orientation of the TRPV2 lower gate and ankyrin repeat domains favored that of agonist-activated TRPV1, suggesting some common properties of TRPV channel open conformations. We propose that these newly revealed structural features contribute to non-selective cation conductance, explaining constitutive activity of TRPV2 and other TRP family members involved in sensory perception and human disease.