Activated
macrophages play an important role in many inflammatory diseases
including septic shock and atherosclerosis. However, the molecular
mechanisms limiting macrophage activation are not completely understood.
Members of the tripartite motif (TRIM) family have recently emerged as important players in innate immunity and antivirus. Here, we systematically analyzed mRNA expressions of representative TRIM molecules in human THP1-derived macrophages activated by different Toll-like receptor (TLR) ligands.
Twenty-nine TRIM members were highly induced by one or more TLR ligands, among which 19 of them belong to TRIM C-IV subgroup.
Besides TRIM21, TRIM22 and TRIM38 were shown to be upregulated by TLR3 and TLR4 ligands as previous reported, we identified a novel group of TRIM genes (TRIM14, 15, 31, 34, 43, 48, 49, 51 and 61) that were significantly up-regulated by TLR3 and TLR4 ligands.
In contrast, the expression of TRIM59 was down-regulated by TLR3 and TLR4 ligands in both human and mouse macrophages.
The alternations of the TRIM proteins were confirmed by Western blot. Finally, overexpression of TRIM59 significantly suppressed LPS-induced macrophage activation, whereas siRNA-mediated knockdown of TRIM59 enhanced LPS-induced macrophage activation.
Taken together, the study provided an insight into the TLR ligands-induced expressions of TRIM family in macrophages.
Members of the tripartite motif (TRIM) family have recently emerged as important players in innate immunity and antivirus. Here, we systematically analyzed mRNA expressions of representative TRIM molecules in human THP1-derived macrophages activated by different Toll-like receptor (TLR) ligands.
Twenty-nine TRIM members were highly induced by one or more TLR ligands, among which 19 of them belong to TRIM C-IV subgroup.
Besides TRIM21, TRIM22 and TRIM38 were shown to be upregulated by TLR3 and TLR4 ligands as previous reported, we identified a novel group of TRIM genes (TRIM14, 15, 31, 34, 43, 48, 49, 51 and 61) that were significantly up-regulated by TLR3 and TLR4 ligands.
In contrast, the expression of TRIM59 was down-regulated by TLR3 and TLR4 ligands in both human and mouse macrophages.
The alternations of the TRIM proteins were confirmed by Western blot. Finally, overexpression of TRIM59 significantly suppressed LPS-induced macrophage activation, whereas siRNA-mediated knockdown of TRIM59 enhanced LPS-induced macrophage activation.
Taken together, the study provided an insight into the TLR ligands-induced expressions of TRIM family in macrophages.
Macrophages
are the major components of innate immunity that enable the body to
combat bacteria and other pathogens.
However, over-activation of macrophages plays a central role in a variety of inflammatory diseases, such as septic shock, atherosclerosis, arthritis and inflammatory bowel diseases. In these disease settings, activated macrophages elaborate a large array of cytokines, growth factors and proteolytic enzymes that are critical for tissue damage and repair1,2.
Macrophages are activated in response to the pathogen-associated molecular patterns by various pattern-recognition receptors (PRRs), such as the Toll-like receptors (TLRs) and the RIG-I-like receptors (RLR)3,4.
There are 13 TLRs that sense various pathogen components and trigger intracellular signaling pathways that eventually mediate the induction of inflammatory cytokines, chemokines and type I interferons, which are critical for antimicrobial activity4,5. The molecular mechanisms of regulation of macrophage activation in response to TLR ligands have been largely unknown.
However, over-activation of macrophages plays a central role in a variety of inflammatory diseases, such as septic shock, atherosclerosis, arthritis and inflammatory bowel diseases. In these disease settings, activated macrophages elaborate a large array of cytokines, growth factors and proteolytic enzymes that are critical for tissue damage and repair1,2.
Macrophages are activated in response to the pathogen-associated molecular patterns by various pattern-recognition receptors (PRRs), such as the Toll-like receptors (TLRs) and the RIG-I-like receptors (RLR)3,4.
There are 13 TLRs that sense various pathogen components and trigger intracellular signaling pathways that eventually mediate the induction of inflammatory cytokines, chemokines and type I interferons, which are critical for antimicrobial activity4,5. The molecular mechanisms of regulation of macrophage activation in response to TLR ligands have been largely unknown.
Tripartite
motif (TRIM) proteins contain a RING finger, one or two B-box motifs
and a coiled-coil motif, and are involved in many biological processes
including innate immunity, viral infection, carcinogenesis and
development6.
There are over 70 members of TRIM protein family described in humans7. Recently, several systematic analyses suggest that many TRIM proteins are implicated in the regulation of innate immune pathways and anti-viral activities8,9,10,11. For example, Carthagena et al. identified 27 of the 72 human TRIM genes are sensitive to interferon (IFN) by performing a systematic analysis of TRIM gene expressions in human primary lymphocytes and monocyte-derived macrophages in response to IFNs10.
In addition, Rajsbaum et al. found that the genes encoding a subset of TRIM proteins located on chromosome 7 were up-regulated by type I IFN in macrophages/DC, suggesting that they may have anti-viral functions11.
TRIM8 negatively regulates PIAS3-mediated repression of NF-κB by inducing translocation of PIAS3 from nucleus to cytoplasm as well as its turnover12,13,14, whereas TRIM16 (also known as EBBP) was reported to promote IL-1β secretion. TRIM22 is involved in anti-viral pathways by activating NF-κB signaling15,16,17,18. TRIM30 induces the lysosomal degradation of TAB2 and TAB3, thereby negatively regulating NF-κB induction in the LPS-triggered TLR4 signaling pathway19. TRIM21 negatively regulates TLR3, −4, −7, and −9 and RLR signaling pathways by modulating the activities of IKKs and interferon regulatory factors (IRFs)20,21. TRIM27 targets all IKKs and negatively regulates the PRR pathways21,22. CARD domain ubiquitination by TRIM25 is essential for RIG-I-mediated type I interferon induction21,23. TRIM56 facilitates double-strand DNA-stimulated interferon induction by ubiquitination of STING (stimulator of interferon genes)21,24. However, the functions of most of TRIM family members remain to be characterized.
There are over 70 members of TRIM protein family described in humans7. Recently, several systematic analyses suggest that many TRIM proteins are implicated in the regulation of innate immune pathways and anti-viral activities8,9,10,11. For example, Carthagena et al. identified 27 of the 72 human TRIM genes are sensitive to interferon (IFN) by performing a systematic analysis of TRIM gene expressions in human primary lymphocytes and monocyte-derived macrophages in response to IFNs10.
In addition, Rajsbaum et al. found that the genes encoding a subset of TRIM proteins located on chromosome 7 were up-regulated by type I IFN in macrophages/DC, suggesting that they may have anti-viral functions11.
TRIM8 negatively regulates PIAS3-mediated repression of NF-κB by inducing translocation of PIAS3 from nucleus to cytoplasm as well as its turnover12,13,14, whereas TRIM16 (also known as EBBP) was reported to promote IL-1β secretion. TRIM22 is involved in anti-viral pathways by activating NF-κB signaling15,16,17,18. TRIM30 induces the lysosomal degradation of TAB2 and TAB3, thereby negatively regulating NF-κB induction in the LPS-triggered TLR4 signaling pathway19. TRIM21 negatively regulates TLR3, −4, −7, and −9 and RLR signaling pathways by modulating the activities of IKKs and interferon regulatory factors (IRFs)20,21. TRIM27 targets all IKKs and negatively regulates the PRR pathways21,22. CARD domain ubiquitination by TRIM25 is essential for RIG-I-mediated type I interferon induction21,23. TRIM56 facilitates double-strand DNA-stimulated interferon induction by ubiquitination of STING (stimulator of interferon genes)21,24. However, the functions of most of TRIM family members remain to be characterized.
In
the present study, we systematically profiled the expressions of TRIM
gene family in human THP1-derived macrophages activated by different TLR
ligands. The up-regulated or down-regulated TRIM genes were further
confirmed by quantitative real-time polymerase chain reaction (qRT-PCR)
and Western blot analysis. The function of TRIM59 in macrophage
activation was further studied.
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