P2X7 Receptors and TMEM16 Channels Form a Hub with Implications for Macropore Formation and Current Facilitation

Abstract

P2X7 receptors (P2X7) are cationic channels involved in many diseases. They exhibit unique behaviors, such as “macropore” formation, which corresponds to enhanced large molecule cell membrane permeability, and current facilitation, which is caused by prolonged activation. These two phenomena have often been confounded, but thus far no clear mechanisms have been resolved. Here we provide evidence that current facilitation and macropore formation involve functional complexes comprised of P2X7 and TMEM16, a family of Ca2+-activated ion channel/scramblases. We found that current facilitation results in an increase of complex-embedded P2X7 open channel probability, a result mimicked by plasma membrane cholesterol depletion. We further show that macropore formation entails two distinct large molecule permeation components, one of which requires protein complexes featuring TMEM16F subtype, the other likely being direct permeation through the P2X7 pore itself. Such protein complexes can be considered to represent a regulatory hub intimately involved in distinct P2X7 functionalities.