Arthritis & Rheumatism, Volume 60,
October 2009 Abstract Supplement
The 2009 ACR/ARHP Annual Scientific Meeting
Philadelphia October 16-21, 2009.
Autoantigen TRIM21/Ro52 Contributes to Suppression of NF-B-Dependent Cytokine Expression in Fibroblasts
Yoshimi1, Ryusuke, Chang1, Tsung-Hsien, Wang2, Hongsheng, Atsumi1, Toru, Morse III2, Herbert C., Ozato1, Keiko
National Institute of Child Health and Human Development. National Institutes of Health, Bethesda, MD
National Institute of Allergy and Infectious Diseases. National Institutes of Health, Rockville, MD
The tripartite motif (TRIM) family member, TRIM21, is an autoantigen known as Ro52/SS-A, which is recognized by antibodies in sera of patients with systemic lupus erythematosus (SLE) and Sjögren's syndrome (SS). Although it has been shown that TRIM21 is an E3 ubiquitin ligase for IRF3 and IRF8 that functions in both innate and acquired immunity, its physiological role in vivo has remained unclear. Here we investigated the in vivo function of TRIM21 using a gene disruption strategy.
We generated Trim21-/- mice with the Trim21 gene replaced by an EGFP reporter. The populations of leukocyte subsets and detailed expression pattern of TRIM21 were investigated using Trim21-/- mice. We stimulated immune cells from Trim21+/+ and Trim21-/- mice and tested cytokine induction, cell proliferation and antibody production. Mice were immunized by specific antigen for in vivo Ig production. We also performed promoter analyses using a NF-kB-driven luciferase reporter, ubiquitylation assays for IRF3 and IRF8 and quantitative RT-PCR for gene expression.
Trim21-/- mice were born with the expected Mendelian ratio and young adult mice showed no gross abnormality. The populations of leukocyte subsets in thymus, spleen and lymph nodes were also normal in Trim21-/- mice. EGFP expression analyses revealed that Trim21 was widely expressed in many tissues, with the highest levels in immune cells. Studies of Trim21-/- embryonic fibroblasts demonstrated that TLR-mediated induction of proinflammatory cytokines, including IL-1b, IL-6, TNFa and CXCL10, was consistently upregulated relative to wild-type cells. Reporter analyses revealed that TLR-mediated NF-kB activation was higher in Trim21-/- cells than in wild-type cells, accounting for their enhanced cytokine expression. However, functional analyses of immune cells from Trim21-/- mice demonstrated no abnormalities in their composition or function, even though ubiquitylation of IRF3 and IRF8 was impaired. Consistent with possible redundancies in TRIM21-mediated activities, we found that a number of TRIM family members were upregulated in Trim21-/- cells.
TRIM21 functions as a negative regulator in NF-kB-dependent proinflammatory cytokine responses in fibroblasts. It may contribute to regulation of inflammation in the pathogenesis of SLE and SS.
To cite this abstract, please use the following information:
Yoshimi, Ryusuke, Chang, Tsung-Hsien, Wang, Hongsheng, Atsumi, Toru, Morse III, Herbert C., Ozato, Keiko; Autoantigen TRIM21/Ro52 Contributes to Suppression of NF-B-Dependent Cytokine Expression in Fibroblasts [abstract]. Arthritis Rheum 2009;60 Suppl 10 :1330