Pannexin

A pannexin is a member of a vertebrate family of proteins homologous to the invertebrate innexins. Innexins are responsible for forming gap junctions in invertebrates. While pannexins are demonstrated to form channels that allow release of ATP in erythrocytes and taste receptor cells, epoxyeicosatrienoic acids in erythrocytes, and IL1-β in macrophage, their role as gap junctions is not yet confirmed in vivo. In addition to pannexins, vertebrate genomes encodes a much larger family of connexins responsible for gap junction formation. So far three pannexins were described in rodent and human genomes: Panx1, Panx2 and Panx3. Hypothetical roles of pannexins in the nervous system include participating in sensory processing, synchronization between hippocampus and cortex, hippocampal plasticity, and propagation of the calcium waves. Calcium waves are supported by glial cells, which help maintain and modulate neuronal metabolism. According to one of the hypothesis, Pannexins also may participate in pathological reactions, including the neural damage after ischemia and subsequent cell death. Pannexins may also be involved in the process of tumorigenesis. Particularly, PANX2 expression levels predict post diagnosis survival for patients with glial tumors.