ATP and large signaling metabolites flux through caspase-activated Pannexin 1 channels

Abstract

Pannexin 1 (Panx1) is a membrane channel implicated in numerous physiological and pathophysiological processes via its ability to support release of ATP and other cellular metabolites for local intercellular signaling. However, to date, there has been no direct demonstration of large molecule permeation via the Panx1 channel itself, and thus the permselectivity of Panx1 for different molecules remains unknown. To address this, we expressed, purified, and reconstituted Panx1 into proteoliposomes and demonstrated that channel activation by caspase cleavage yields a dye-permeable pore that favors flux of anionic, large-molecule permeants (up to ~1 kDa). Large cationic molecules can also permeate the channel, albeit at a much lower rate. We further show that Panx1 channels provide a molecular pathway for flux of ATP and other anionic (glutamate) and cationic signaling metabolites (spermidine). These results verify large molecule permeation directly through caspase-activated Panx1 channels that can support their many physiological roles.

Structure versus function: Are new conformations of pannexin 1 yet to be resolved?

“…Frog Panx1 was subsequently found to exhibit similar voltage-sensitive properties (Michalski et al, 2020). In contrast, complete absence of voltage activation has been reported for human and frog Panx1, while mouse Panx1 was found to be weakly voltage sensitive (Chekeni et al, 2010;Chiu et al, 2018;Narahari et al, 2021).…”

Panx1 channels promote both anti- and pro-seizure-like activities in the zebrafish via p2rx7 receptors and ATP signaling

“…Hypotheses regarding Panx1s’ involvement in epileptic seizures vary, with evidence pointing towards the ability to release the neurotransmitter ATP 8,9 51 . Reports show extracellular ATP is reduced in brain tissue preparations deriving from mice with global loss of Panx1 9,52,53 , or astrocytic deletion of Panx1 14 , and extracellular ATP concentrations increase during high levels of neuronal activity and seizure-like events 54,55 .…”

Pannexin 1 as a driver of inflammation and ischemia–reperfusion injury

“…Pannexins form large conductance, relatively non-selective channels that can mediate permeability of both anionic and cationic molecules up to 1 kDa in size [26]. Molecules passively diffuse through Panx1 channels, following concentration gradients, and as solute size increases, the permselectivity of Panx1 favors anions over cations [27].…”