The pannexin gene family encodes a second class of putative gap junction proteins and is highly conserved in invertebrates and mammals. Pannexins (Panx) are four-pass transmembrane proteins that oligomerize to form large pore ion and metabolite-permeable channels. Pannexin-1 (PANX1) and Pannexin-3 are closely related, while Pannexin-2 is a more distant relation. PANX1 is a transmembrane protein that forms a mechanosensitive ATP-permeable channel between adjacent cells and in the endoplasmic reticulum. PANX1 may play a role as a Ca2+ -leak channel to regulate ER Ca2+ homeostasis and regulates neural stem and progenitor cell proliferation.
