The TRAF6, but not the TRAF2/3, binding domain of CD40 is required for cytokine production in human lung fibroblasts.
Fibroblasts are key effector cells in inciting inflammation, wound healing, and scarring. CD40, a member of the TNF receptor superfamily, mediates intercellular communication between fibroblasts and cells that express CD154 (CD40L), including T lymphocytes and platelets. To better understand the mechanisms by which CD40 regulates fibroblast function in inflammation and scarring, we examined the ability of CD40 cytoplasmic tail regions (CD40ct) containing the TRAF6 or the TRAF2/3 binding domains to regulate cytokine and chemokine expression by primary human lung fibroblasts. The full-length human CD40ct, the first 35 amino acids of the CD40ct encompassing the TRAF6 binding site (1-35), and amino acids 35-53 containing the TRAF2/TRAF3 binding domain were expressed in human lung fibroblasts as fusion proteins with the extracellular domain of human CD8alpha by retroviral transduction. The TRAF6, but not the TRAF2/3, binding domain was found to regulate IL-8 and IL-6 production, and induce activation of NF-kappaB and Jun kinase in lung fibroblasts, demonstrating for the first time that CD40ct domains can function independently to regulate pro-inflammatory responses of primary human fibroblasts. Thus, targeting TRAF6 function through pharmacological intervention may represent a viable strategy for modulating localized inflammation.
Purkerson
Jeffrey M
JM
Department of Pediatrics, University of Rochester Medical Center, Rochester, NY 14642, USA. jeffrey_purkerson@urmc.rochester.edu
Smith
Roger S
RS
Pollock
Stephen J
SJ
Phipps
Richard P
RP
D048868:Adaptor Proteins, Signal Transducing / Q000276:immunology / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D019013:CD40 Antigens / Q000276:immunology* / Q000378:metabolism; D002478:Cells, Cultured; D016207:Cytokines / Q000276:immunology*; D024202:Electrophoretic Mobility Shift Assay; D004789:Enzyme Activation / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D005347:Fibroblasts / Q000276:immunology*; D006801:Humans; D007150:Immunohistochemistry; D008168:Lung / Q000276:immunology*; D008969:Molecular Sequence Data; D017385:Sequence Homology; D048008:TNF Receptor-Associated Factor 3; D048029:TNF Receptor-Associated Factor 6 / Q000276:immunology* / Q000378:metabolism; D047988:Tumor Necrosis Factor Receptor-Associated Peptides and Proteins / Q000276:immunology / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D019013:CD40 Antigens; D016207:Cytokines; C446759:TIFA protein, human; D048008:TNF Receptor-Associated Factor 3; D048029:TNF Receptor-Associated Factor 6; C090656:TRAF3 protein, human; D047988:Tumor Necrosis Factor Receptor-Associated Peptides and Proteins