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Rab 14 regulates tight junction integrity and epithelial
polarity
Debra Johnson 1 , Kelsey Waite 1 , Natasha Sinha 1 , Dogukan Dalgalan 1 , Jean Wilson 1 .
Department of Cell Biology, University of Arizona, Tucson, AZ 1
Abstract:
The establishment and maintenance of the epithelial tight junction is critical to the normal
function of epithelial organs, both to serve as a selectively permeable barrier and for the
maintenance of epithelial polarity. Membrane traffic plays an essential role in the establishment
and maintenance of both tight junctions and polarity, but the molecular players in this process
remain unclear. We have found that the small GTPase Rab14 regulates the establishment and
maintenance of tight junctions and polarity in MDCK cells. We show that expression of an
inactive mutant of Rab14 results in more rapid formation of tight junctions after calcium switch;
this is likely due to decreased endocytosis of tight junction components, as endocytosis of
occludin is inhibited in cell expressing inactive Rab14. Furthermore, confocal imaging indicates
that Rab14 colocalizes with a subset of occludin- and claudin-1-positive vesicles. Furthermore,
knockdown of Rab14 results in redistribution of claudin-1 to a perinuclear compartment.
Finally, expression of inactive Rab14 prevents the cells from forming single lumen cysts in threedimensional
culture. These effects may be mediated by a previously unrecognized apical
endosomal multi-protein complex, as Rab14 interacts with the apical endosomal protein
endotubin and the polarity regulator aPKC. This complex may serve to organize and target tight
junction proteins after endocytosis to maintain the epithelial barrier.