Electronic Thesis and Dissertation Repository


Master of Science


Anatomy and Cell Biology


Laird, Dale W.


The channel-forming membrane protein pannexin 1 (Panx1) is best characterized as an ATP release channel and has been linked to over a dozen human pathologies. Along with protein- protein interactions and post-translational modifications, the physiological function of Panx1 channels is highly dictated by its subcellular localization. In polarized epithelial cells in vivo, Panx1 is reported to selectively localize to distinct plasma membrane domains. Here, we investigated whether this polarized distribution is guided by internal motifs contained within the Panx1 polypeptide. In polarized MDCK cells, Panx1 was localized predominantly at the apical membrane domain, although a subset remained detectable in the basolateral cell surface. In non-polarized cells, Panx1 localized throughout the entire plasma membrane, including the lamellipodia of migratory tumor cells. The membrane distribution of Panx1 remained unchanged upon mutation of a dileucine motif in the C-terminal domain, indicating that this motif is not responsible for basolateral Panx1 protein sorting in polarized cells. Interestingly, stable expression of a Panx1 mutant where a putative tyrosine-based sorting motif was eliminated caused MDCK cells to lose the ability to polarize and undergo a phenotypic switch consistent with an epithelial-to-mesenchymal transition (EMT). MDCK cells expressing a truncated mutant of Panx1 exhibited a similar EMT-like phenotypic change and additionally failed to polarize. Taken together, our data indicate that polarized trafficking of Panx1 does not depend upon the dileucine motif, and that the expression of Panx1 mutants may play a role in regulating the epithelial cell phenotype.