Abstract
Inflammatory processes disrupt the barrier function in epithelia. Increased permeability often leads to chronic of inflammation. Important among other cytokines, tumor necrosis factor alpha (TNF-α) initiates an NF-κB-mediated response that leads to upregulation of myosin light chain kinase (MLCK), a hallmark of the pathogenesis of inflammatory bowel disease. Here, we found that two components of the evolutionarily conserved organizer of tight junctions and polarity, the polarity complex (atypical protein kinase C [aPKC]-PAR6-PAR3) were downregulated by TNF-α signaling in intestinal epithelial cells and also in vivo during intestinal inflammation. Decreases in aPKC levels were due to decreased chaperoning activity of Hsp70 proteins, with failure of the aPKC rescue machinery, and these effects were rescued by NF-κB inhibition. Comparable downregulation of aPKC shRNA phenocopied effects of TNF-α signaling, including apical nonmuscle myosin II accumulation and myosin light chain phosphorylation. These effects, including ZO-1 downregulation, were rescued by overexpression of constitutively active aPKC. We conclude that this novel mechanism is a complementary effector pathway for TNF-α signaling.
Publication types
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Research Support, N.I.H., Extramural
MeSH terms
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Adaptor Proteins, Signal Transducing / metabolism
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Animals
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Base Sequence
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Caco-2 Cells
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Cell Cycle Proteins / metabolism
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Cell Polarity
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HSC70 Heat-Shock Proteins / metabolism
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HSP70 Heat-Shock Proteins / deficiency
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HSP70 Heat-Shock Proteins / genetics
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HSP70 Heat-Shock Proteins / metabolism
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Humans
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Inflammation / genetics
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Inflammation / metabolism*
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Inflammatory Bowel Diseases / etiology
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Inflammatory Bowel Diseases / genetics
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Inflammatory Bowel Diseases / metabolism
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Intestinal Mucosa / drug effects*
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Intestinal Mucosa / metabolism*
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Membrane Proteins / metabolism
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Mice
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Mice, Knockout
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Molecular Motor Proteins / genetics
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Molecular Motor Proteins / metabolism
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Multiprotein Complexes
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Myosin Heavy Chains / genetics
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Myosin Heavy Chains / metabolism
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Protein Kinase C / antagonists & inhibitors
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Protein Kinase C / genetics
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Protein Kinase C / metabolism
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Protein Processing, Post-Translational
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RNA, Small Interfering / genetics
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Signal Transduction
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Tight Junctions / metabolism
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Tumor Necrosis Factor-alpha / metabolism
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Tumor Necrosis Factor-alpha / pharmacology*
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Up-Regulation
Substances
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Adaptor Proteins, Signal Transducing
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Cell Cycle Proteins
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HSC70 Heat-Shock Proteins
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HSP70 Heat-Shock Proteins
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HSPA8 protein, human
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MYH9 protein, human
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Membrane Proteins
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Molecular Motor Proteins
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Multiprotein Complexes
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PARD3 protein, human
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PARD6A protein, human
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RNA, Small Interfering
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Tumor Necrosis Factor-alpha
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PKC-3 protein
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Protein Kinase C
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Myosin Heavy Chains