Structural insights into the organization and channel properties of human Pannexin isoforms 1 and 3

Abstract

Pannexins are single-membrane large-pore ion channels that release ATP upon activation. Three isoforms of pannexins, 1, 2, and 3, perform diverse cellular roles, including inflammation, differentiation, neuropathic pain, and ATP release. In this study, we report the cryoEM structure of pannexin 3 at 3.9 Å and characterize the structural differences with pannexin isoforms 1 and 2. We observe the organization of the Pannexin 3 vestibule into two distinct chambers with a wider pore radius in comparison to both PANX1 and 2 isoforms. We further report the structure of pannexin1 congenital mutant R217H in the resolution range of 3.9 Å. The congenital mutant R217H in transmembrane helix3 (TM3), R217H induce structural changes that leads to a partially closed pore and altered ATP interaction propensities. The channel conductance of the congenital mutant displays weakened voltage sensitivity. The results showcase a complete comparison of the three pannexin isoform structures that along with the structure of Pannexin 1 congenital mutant highlight distinct structural features of pannexin isoforms and the allosteric role of distant substitutions in dictating channel behavior in Pannexin 1.