AUF1 isoform-specific regulation of anti-inflammatory IL10 expression in monocytes.
IL-10 is an immunomodulatory cytokine that regulates inflammatory responses of mononuclear phagocytes (monocytes and macrophages). Mononuclear cells exposed to microbes or microbial products secrete a host of proinflammatory cytokines followed by delayed onset of anti-inflammatory IL-10. IL-10 suppresses immune responses by inhibiting cytokine production by mononuclear phagocytes. Using THP-1, a human promonocytic leukemia cell line, we show that endotoxin/lipopolysaccharide (LPS) exposure induces IL10 expression while IFN-gamma blocks this LPS-mediated effect. IFN-gamma is an important modulator of IL-10 production during infectious diseases. We show that LPS and IFN-gamma regulate IL10 expression in THP-1 cells in part through posttranscriptional mechanisms. Our results demonstrate that 3'-untranslated region (3'-UTR) AU-rich elements (AREs) decrease expression of a chimeric luciferase reporter gene in THP-1 cells. The ARE-binding protein AUF1 binds the IL10 3'-UTR. Depletion of AUF1 by RNAi suppresses LPS-mediated induction of IL10 mRNA and protein without affecting LPS-mediated stabilization of IL10 mRNA. Upon complementation with either RNAi-refractory p37 or p40 AUF1 plasmids, only p40 restores LPS-mediated induction of IL10 mRNA and protein to near normal levels. Thus, the p40 AUF1 isoform selectively plays a critical, positive role in IL10 expression upon LPS exposure.
Sarkar
Srijata
S
Department of Molecular Genetics, Microbiology, and Immunology, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA. pestka@umdnj.edu
Sinsimer
Kristina S
KS
Foster
Randi L
RL
Brewer
Gary
G
Pestka
Sidney
S
D002460:Cell Line; D005786:Gene Expression Regulation; D055785:Gene Knockdown Techniques; D000081035:Heterogeneous Nuclear Ribonucleoprotein D0; D034502:Heterogeneous-Nuclear Ribonucleoprotein D / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism; D016753:Interleukin-10 / Q000235:genetics / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000378:metabolism; D008262:Macrophage Activation; D009000:Monocytes / Q000378:metabolism*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000276:immunology / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics
C000630986:HNRNPD protein, human; D000081035:Heterogeneous Nuclear Ribonucleoprotein D0; D034502:Heterogeneous-Nuclear Ribonucleoprotein D; D008070:Lipopolysaccharides; D020033:Protein Isoforms; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D016753:Interleukin-10; D007371:Interferon-gamma