Trafficking Dynamics of Glycosylated Pannexin1 Proteins

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Abstract
Pannexins are mammalian orthologs of innexins and have a predicted topological folding pattern similar to that of connexins, except they are glycosylated. Rat pannexin1 is glycosylated at N254 and this residue is important for plasma membrane targeting. Here we demonstrate that cell surface expression levels of the rat pannexin1 N254Q mutant are rescued by coexpression with the wild-type protein. In paired Xenopus oocytes, the functional effect of this rescue is inconsequential; however, cell surface deglycosylation by PNGase F significantly enhanced functional gap junction formation. In mammalian cells, wild-type oligomers traffic at a slower rate than Myc-or tetracysteine domain–tagged versions, a behavior opposite to that of tagged connexins. The temporal differences of Panx1 trafficking correlate with spatial differences of intracellular localizations induced by Golgi blockage by Brefeldin-A or glycosylation prevention by tunicamycin. Therefore, Panx1 has kinetics and dynamics that make it unique to serve distinct functions separate from connexin-based channels.