Presentation
PTK6 Mediates TNFα Driven Intestinal Epithelial Barrier Dysfunction by Activation of Focal Adhesion Kinase
Digestive Disease Week
(2016)
Abstract
Epithelial barrier dysfunction is a critical pathological event in the development of several inflammatory diseases in the gut. Hyperpermeability of intestinal epithelium can lead to excessive leukocyte activation and directly contribute to intestinal inflammation. Therefore, an attractive treatment strategy for those with chronic inflammatory disorders of the gut is to decrease the potential for epithelial hyperpermeability to stave off flare-ups. Early events in aberrant epithelial permeability involve inflammation mediated signaling events such as post-translational modification of proteins that loosen the cell-cell contacts, as well as intercellular gap formation due to the contraction of cytoskeletal components. Later events that contribute to prolonged permeability are the consequence of gene regulatory events, such as downregulation of tight junction proteins that occur in response to extracellular signals. PTK6 phosphorylates several proteins that are responsible for regulating the integrity of tight junctions in a manner that promotes loosening of cell junctions, and is also involved in the gene regulatory events in that it associates with several transcription factors in the nucleus and modulates their activity (such as beta catenin). Since PTK6 is involved in gene regulatory events as well as the acute phase of epithelial hyperpermeability, it may be an ideal target for treating inflammatory disorders of the gut at any stage of disease (latent or active). Our lab has recently shown the critical role of PTK6 on intestinal epithelial barrier function in that PTK6-/- cells displayed an improvement of epithelial barrier function than that of PTK6 +/+ cells in response to TNFα/IFNγ. In this study we aimed to further elucidate a mechanism for PTK6 mediated epithelial hyperpermeability in response to TNFα/IFNγ. Since FAK has been shown to play a key role in mediating tight junction dissolution in response to inflammatory signals in the gut, and PTK6 phosphorylates FAK, we hypothesized that PTK6 targeting of FAK was a critical factor in inflammation mediated epithelial hyperpermeability. We show that knocking down PTK6 in YAMC impaired TNFα/IFNγmediated FAK activation via diminished detection of FAK phosphorylation at Y397. We also show that cells with PTK6 gene interruption display significantly less pY397 FAK following cytokine treatment. In addition, PTK6 reintroduction to PTK6-/- cells increased FAK activation in response to TNFα. furthermore, in vitro permeability assays support the hypothesis that PTK6-FAK pathway contributes to the barrier dysfunction resulting from TNFα. These results suggest that PTK6 dependent FAK phosphorylation is a critical event in intestinal epithelial hyperpermeability.
Disciplines
Publication Date
May 24, 2016
Location
San Diego, CA
Citation Information
Ricci J. Haines, Richard S. Beard and Mack Wu. "PTK6 Mediates TNFα Driven Intestinal Epithelial Barrier Dysfunction by Activation of Focal Adhesion Kinase" Digestive Disease Week (2016) Available at: http://works.bepress.com/richard-beard/10/