Proteins of the SNX (sorting nexin) superfamily are characterized by the presence of a PX (Phox homology) domain and associate with PtdIns3P (phosphatidylinositol-3-monophosphate)-rich regions of the endosomal system. SNX27 is the only sorting nexin that contains a PDZ domain. In the present study, we used a proteomic approach to identify a novel interaction between SNX27 and ZO-2 [zonula occludens-2; also known as TJP2 (tight junction protein 2)], a component of the epithelial tight junction. The SNX27–ZO-2 interaction requires the PDZ domain of SNX27 and the C-terminal PDZ-binding motif of ZO-2. When tight junctions were perturbed by chelation of extracellular Ca2+, ZO-2 transiently localized to SNX27-positive early endosomes. Depletion of SNX27 in mpkCCD (mouse primary kidney cortical collecting duct) cell monolayers resulted in a decrease in the rate of ZO-2, but not ZO-1, mobility at cell–cell contact regions after photobleaching and an increase in junctional permeability to large solutes. The findings of the present study identify an important new SNX27-binding partner and suggest a role for endocytic pathways in the intracellular trafficking of ZO-2 and possibly other tight junction proteins. Our results also indicate a role for SNX27–ZO-2 interactions in tight junction maintenance and function.
Sorting nexin 27 (SNX27) associates with zonula occludens-2 (ZO-2) and modulates the epithelial tight junction
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Seth P. Zimmerman, Christina L. Hueschen, Daniela Malide, Sharon L. Milgram, Martin P. Playford; Sorting nexin 27 (SNX27) associates with zonula occludens-2 (ZO-2) and modulates the epithelial tight junction. Biochem J 1 October 2013; 455 (1): 95–106. doi: https://doi.org/10.1042/BJ20121755
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