A cellular metabolite directly and reversibly opens the ATP release pannexin channels.

Abstract

Pannexins (Panx1-3) are a broadly expressed family of ion channels which mediate the cellular release of signaling molecules such as ATP. There are many established roles of pannexins in cell signaling and pathophysiology, particularly in the immune, cardiovascular, and nervous systems. Notably, Panx1 opens irreversibly following cleavage of its C-terminus by caspases in apoptotic cells, releasing ATP to recruit nearby phagocytes. However, there are many signaling roles of pannexin in non-apoptotic cells, which dictates that a reversible mode of activation must exist. To date, a number of post-translational modifications have been proposed as such candidates. Nevertheless, these findings typically relied on cell-based experiments and the simultaneous use of large, supraphysiological voltages to assess changes in channel function. Thus, it is unclear whether they act themselves as a channel gating stimulus or act as modulators. Based on our previous work, we postulated that small molecules may act as a natural gating stimulus for pannexins. An unbiased screen of cellular metabolites obtained from mouse tissues revealed a candidate pannexin agonist. Electrophysiological, cell-based, and in vitro assays confirmed that these metabolites act directly on pannexins to reversibly open the channel and trigger ATP release at resting membrane potential. These data establish this molecule class as the first bona fide pannexin agonists, and elucidate a novel biochemical pathway leading to ATP release through pannexins.