Mammalian Scribble regulates the assembly of epithelial tight junctions

Abstract

Scribble, Disc‐large (DLG), and Lethal giant larvae (LGL) tumor suppressor proteins have been implicated in the regulation of epithelial cell polarity. However, the mechanisms by which these proteins contribute to epithelial polarity are not well understood. Since tight junctions (TJs) play an important role in regulating intestinal epithelial cell (IEC) polarity and barrier function, we examined if these proteins participate in TJ dynamics and in the establishment of the IEC barrier function. Model IECs, SK‐CO15 and T84 cells were used for these studies, and TJ assembly/disassembly was analyzed using the calcium switch assay. Fluorescence labeling/confocal microscopy demonstrated that Scribble and LGL1 but not DLG1 co‐localized with TJ proteins, occludin and zonula occludens‐1. Additionally, Scribble and LGL1 co‐internalized with the TJ proteins during TJ disassembly induced by calcium depletion. Furthermore, siRNA‐mediated downregulation of Scribble, but not LGL1 or DLG1 significantly attenuated the functional and morphologic assembly of TJs during calcium repletion. Downregulation of Scribble did not influence expression of DLG1 or LGL1 and vise versa, and these proteins did not co‐associate as determined by immunoprecipitation. In conclusion, we demonstrate a unique role of mammalian Scribble in regulation of IEC TJ assembly and in the development of epithelial barrier function.Supported by CCFA Career Development Award (AII), NIH DK‐59888 (AN), and NIH DK‐55567 (AN)