Structures of human pannexin 1 reveal ion pathways and mechanism of gating

Pannexin 1 (PANX1) is an ATP-permeable channel with critical roles in a variety of

physiological functions such as blood pressure regulation 1 , apoptotic cell clearance 2

and human oocyte development 3 . Here we present several structures of human PANX1

in a heptameric assembly at resolutions of up to 2.8 angström, including an apo state,

a caspase-7-cleaved state and a carbenoxolone-bound state. We reveal a gating

mechanism that involves two ion-conducting pathways. Under normal cellular

conditions, the intracellular entry of the wide main pore is physically plugged by the

C-terminal tail. Small anions are conducted through narrow tunnels in the

intracellular domain. These tunnels connect to the main pore and are gated by a long

linker between the N-terminal helix and the first transmembrane helix. During

apoptosis, the C-terminal tail is cleaved by caspase, allowing the release of ATP

through the main pore. We identified a carbenoxolone-binding site embraced by W74

in the extracellular entrance and a role for carbenoxolone as a channel blocker. We

identified a gap-junction-like structure using a glycosylation-deficient mutant, N255A.

Our studies provide a solid foundation for understanding the molecular mechanisms

underlying the channel gating and inhibition of PANX1 and related large-pore

channels.