LIGHT signals directly to intestinal epithelia to cause barrier dysfunction via cytoskeletal and endocytic mechanisms.
OBJECTIVE
LIGHT (lymphotoxin-like inducible protein that competes with glycoprotein D for herpes virus entry on T cells) is a tumor necrosis factor core family member that regulates T-cell activation and causes experimental inflammatory bowel disease. Additional data suggest that LIGHT may be involved in the pathogenesis of human inflammatory bowel disease. The aim of this study was to determine if LIGHT is capable of signaling directly to intestinal epithelia and to define the mechanisms and consequences of such signaling.


METHODS
The effects of LIGHT and interferon-gamma on barrier function, cytoskeletal regulation, and tight junction structure were assessed in mice and intestinal epithelial monolayers.


RESULTS
LIGHT induced barrier loss in cultured epithelia via myosin II regulatory light chain (MLC) phosphorylation; both barrier loss and MLC phosphorylation were reversed by MLC kinase (MLCK) inhibition. Pretreatment with interferon-gamma, which induced lymphotoxin beta receptor (LT beta R) expression, was required for these effects, and neither barrier dysfunction nor intestinal epithelial MLC phosphorylation occurred in LT beta R knockout mice. In cultured monolayers, endocytosis of the tight junction protein occludin correlated with barrier loss. Internalized occludin colocalized with caveolin-1. LIGHT-induced occludin endocytosis and barrier loss were both prevented by inhibition of caveolar endocytosis.


CONCLUSIONS
T cell-derived LIGHT activates intestinal epithelial LT beta R to disrupt barrier function. This requires MLCK activation and caveolar endocytosis. These data suggest a novel role for LIGHT in disease pathogenesis and suggest that inhibition of MLCK-dependent caveolar endocytosis may represent an approach to restoring barrier function in inflammatory bowel disease.
Schwarz
Brad T
BT
Department of Pathology, University of Chicago, Chicago, Illinois 60637, USA.
Wang
Fengjun
F
Shen
Le
L
Clayburgh
Daniel R
DR
Su
Liping
L
Wang
Yingmin
Y
Fu
Yang-Xin
YX
Turner
Jerrold R
JR
D000818:Animals; D018938:Caco-2 Cells; D024722:Cardiac Myosins / Q000378:metabolism; D021941:Caveolae / Q000502:physiology; D051242:Caveolin 1 / Q000378:metabolism; D062445:Claudin-1; D003599:Cytoskeleton / Q000502:physiology*; D004705:Endocytosis / Q000502:physiology*; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism*; D053259:Lymphotoxin beta Receptor / Q000096:biosynthesis / Q000172:deficiency; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018994:Myosin Light Chains / Q000378:metabolism; D009219:Myosin-Light-Chain Kinase / Q000037:antagonists & inhibitors; D062793:Occludin; D010539:Permeability / Q000187:drug effects; D010766:Phosphorylation; D015398:Signal Transduction / Q000502:physiology*; D019108:Tight Junctions / Q000187:drug effects / Q000378:metabolism; D014018:Tissue Distribution; D053326:Tumor Necrosis Factor Ligand Superfamily Member 14 / Q000378:metabolism* / Q000494:pharmacology
C568108:CLDN1 protein, human; D051242:Caveolin 1; D062445:Claudin-1; C568113:Cldn1 protein, mouse; D053259:Lymphotoxin beta Receptor; D008565:Membrane Proteins; D018994:Myosin Light Chains; C568985:OCLN protein, human; D062793:Occludin; C568986:Ocln protein, mouse; D053326:Tumor Necrosis Factor Ligand Superfamily Member 14; C107184:myosin light chain 2; D007371:Interferon-gamma; D009219:Myosin-Light-Chain Kinase; D024722:Cardiac Myosins