RalA and RalB differentially regulate development of epithelial tight junctions.
Tight junctions (TJs) are structures indispensable to epithelial cells and are responsible for regulation of paracellular diffusion and maintenance of cellular polarity. Although many interactions between TJ constituents have been identified, questions remain concerning how specific functions of TJs are established and regulated. Here we investigated the roles of Ral GTPases and their common effector exocyst complex in the formation of nascent TJs. Unexpectedly, RNA interference-mediated suppression of RalA or RalB caused opposing changes in TJ development. RalA reduction increased paracellular permeability and decreased incorporation of components into TJs, whereas RalB reduction decreased paracellular permeability and increased incorporation of components into TJs. Activities of both Ral GTPases were mediated through the exocyst. Finally, we show that TJ-mediated separation of apical-basal membrane domains is established prior to equilibration of barrier function and that it is unaffected by Ral knockdown or specific composition of TJs.
Department of Anatomy and Cell Biology, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA.
C Clayton
CC
Hazelett
David
D
Sheff
Charles
C
Yeaman
D000818:Animals; D002460:Cell Line; D004285:Dogs; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D006801:Humans; D019108:Tight Junctions / Q000235:genetics / Q000378:metabolism*; D020725:ral GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
C483163:Ralb protein, human; C492198:RALA protein, human; D020725:ral GTP-Binding Proteins