The mouse interferon-inducible gene Ifi204 product interacts with the Tpr protein, a component of the nuclear pore complex

Sex Differences in Correlation with Gene Expression Levels between Ifi200 Family Genes and Four Sets of Immune Disease-Relevant Genes

Background

The HIN-200 family genes in humans have been linked to several autoimmune diseases—particularly to systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). Recently, its human counterpart gene cluster, the Ifi200 family in mice, has been linked to spontaneous arthritis disease (SAD). However, many immune-mediated diseases (including RA and SLE) show gender difference. Understanding whether or not and how these genes play a role in sex difference in immune-mediated diseases is essential for diagnosis/treatment.

Methods

This study takes advantage of the whole genome gene expression profiles of recombinant inbred (RI) strain populations from female and male mice to analyze potential sex differences in a variety of genes in disease pathways. Expression levels and regulatory QTL of Ifi200 family genes between female and male mice were first examined in a large mouse population, including RI strains derived from C57BL/6J, DBA/2J (BXD), and classic inbred strains. Sex similarities and differences were then analyzed for correlations with gene expression levels between genes in the Ifi200 family and four selected gene sets: known immune Ifi200 pathway-related genes, lupus-relevant genes, osteoarthritis- (OA-) and RA-relevant genes, and sex hormone-related genes.

Results

The expression level of Ifi202b showed the most sex difference in correlation with known immune-related genes (the P value for Ifi202b is 0.0004). Ifi202b also showed gender difference in correlation with selected sex hormone genes, with a P value of 0.0243. When comparing coexpression levels between Ifi200 genes and lupus-relevant genes, Ifi203 and Ifi205 showed significant sex difference (P values: 0.0303 and 0.002, resp.). Furthermore, several key genes (e.g., Csf1r, Ifnb1, IL-20, IL-22, IL-24, Jhdm1d, Csf1r, Ifnb1, IL-20, IL-22, IL-24, and Tgfb2 that regulate sex differences in immune diseases) were discovered.

Conclusions

Different genes in the Ifi200 family play different roles in sex difference among dissimilar pathways of these four gene groups.

p204 Is Required for Canonical Lipopolysaccharide-induced TLR4 Signaling in Mice

p204, a murine member of an interferon-inducible p200 family, was reported to recognize intracellular viral and bacterial DNAs, however, its role in the innate immunity in vivo remains unknown due to the lack of p204-deficient animal models. In this study we first generated the p204^−/− mice. Unexpectedly, p204 deficiency led to significant defect in extracellular LPS signaling in macrophages, as demonstrated by dramatic reductions of LPS-mediated IFN-β and pro-inflammatory cytokines. The serum levels of IFN-β and pro-inflammatory cytokines were also significantly reduced in p204^−/− mice following LPS challenge. In addition, p204^−/− mice were resistant to LPS-induced shock. LPS-activated NF-ĸB and IRF-3 pathways were all defective in p204-deficient macrophages. p204 binds to TLR4 through its Pyrin domain, and it is required for the dimerization of TLR4 following LPS-challenge. Collectively, p204 is a critical component of canonical LPS-TLR4 signaling pathway, and these studies also suggest that p204 could be a potential target to prevent and treat inflammatory and infectious diseases.

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p204 deficiency leads to significant defect in extracellular LPS signaling in macrophages.

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Serum levels of IFN-β and pro-inflammatory cytokines were also significantly reduced in p204^-/- mice following LPS challenge.

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p204^-/- mice were resistant to LPS-induced shock.

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p204 binds to TLR4 through its Pyrin domain, and it is required for the dimerization of TLR4 following LPS-challenge.

Effective anti-pathogenic responses, including production of type I IFNs and inflammatory response, are critical for host defense. p200 family members, including IFI16 and AIM2, have been reported to function as the sensors of pathogen components. However, investigation of their roles has largely focused on intracellular pathogen components, independent of extracellular pathogen receptors, such as TLRs. Here, we provide unexpected evidences demonstrating that p204, a murine counterpart of human IFI16, is required for extracellular but not intracellular LPS signaling. These results provide not only evidence of functional crosstalk and cooperation between intracellular p204 and extracellular LPS through TLR4 pathways in macrophage-mediated innate immunity, but also new insights into the mechanisms underlying p200 family proteins mediated antiviral and antibacterial infections.

Transient expression of interferon-inducible p204 in the early stage is required for adipogenesis in 3T3-L1 cells

A member of the interferon-inducible p200 family of proteins, p204, has recently been reported to function in the development of many mesoderm-derived tissues, such as bone, muscle, and cartilage. However, no published study has yet investigated the role of p204 in adipogenesis. Our preliminary experiments showed that p204 can be found in 3T3-L1 preadipocytes, and its expression was up-regulated in a differentiation-dependent manner. As such, we hypothesized that p204 is associated with adipogenesis and focused on the influence of p204 on adipogenesis. In the present study, we investigated the transient elevated expression and cytoplasm-to-nucleus translocation of p204 in the early stage of adipogenesis. To determine the effect of p204 on adipogenesis, p204-siRNA and expression vector were produced for p204 suppression and overexpression, respectively. The knockdown of p204 resulted in a significantly depressed adipocyte differentiation, whereas p204 overexpression promoted adipocyte differentiation. The mRNA expression of adipogenic markers, such as peroxisome-proliferator-activated receptor (PPAR)gamma, CCAAT/enhancer-binding-protein (C/EBP)alpha, lipoprotein lipase, and adipsin, was decreased by p204 suppression and increased by p204 overexpression. A coimmunoprecipitation assay coupled with an indirect immunofluorescence assay also indicated that p204 interacted and colocalized with C/EBPdelta in the nucleus. Furthermore, the knockdown of p204 disrupted the interaction between p204 and C/EBPdelta and partially suppressed the PPARgamma transcriptional activity by dissociating C/EBPdelta with the PPARgamma promoter element. Collectively, our data indicate that the transient expression of p204 in the early stage is indispensable for adipocyte differentiation. Disruption of p204 expression patterns at this stage leads to irreversible damage in fat formation.

Characterization of nuclear factors modulating the apolipoprotein D promoter during growth arrest: implication of PARP-1, APEX-1 and ERK1/2 catalytic activities

Human Apolipoprotein D (apoD) is upregulated under several stress conditions and pathological situations such as neurodegenerative diseases and cancers. We previously showed that apoD mRNA expression is induced in growth-arrested cells and demonstrated the specific binding of nuclear proteins to the region −514 to −475 of the promoter. Such region contains a pair of Serum Responsive Elements (SRE), an Ets-Binding Site (EBS) and a Glucocorticoid Responsive Element (GRE). In this study, we show that Parp-1, HnRNP-U, CBF-A, BUB-3, Kif4, APEX-1 and Ifi204 bind these regulatory elements of the apoD promoter. Specific binding of HnRNP-U and Parp-1 was confirmed by Electrophoretic Mobility Shift Assay (EMSA). In a biotin pull-down assay, Kif4 and BUB-3 bind preferentially the SRE1 and the EBS-GRE sites, respectively, while APEX-1 seems recruited indirectly to these elements. We found that the mRNA expression of some of these binding factors is upregulated in growth-arrested cells and that these proteins also transactivate the apoD promoter. In agreement with these results, mutants of APEX-1 and of Parp-1 defective for their DNA-binding and catalytic activities could not transactivate the promoter. The knockdown of Parp-1 and HnRNP-U and the use of specific inhibitors of MEK1/2 and of Parp-1 also inhibited the induction of apoD gene expression. Moreover, ERK1/2 was found activated in a biphasic manner post serum-starvation and the inhibition of Parp-1 causes a sustained activation of ERK2 but not ERK1 for up to 2 h. Altogether, these findings demonstrate the importance of Parp-1, APEX-1 and ERK1/2 catalytic activities in the growth arrest-induced apoD gene expression.

p204, a p200 family protein, as a multifunctional regulator of cell proliferation and differentiation

The interferon-inducible p200 family comprises a group of homologous mouse and human proteins. Most of these have an N-terminal DAPIN domain and one or two partially conserved, 200 amino acid long C-terminal domains (designated as 200X domain). These proteins play important roles in the regulation of cell proliferation, tissue differentiation, apoptosis and senescence. p200 family proteins are involved also in autoimmunity and the control of tumor growth. These proteins function by binding to various target proteins (e.g. transcription factors, signaling proteins, oncoproteins and tumor suppressor proteins) and modulating target activity. This review concentrates on p204, a murine member of the family and its roles in regulating cell proliferation, cell and tissue differentiation (e.g. of skeletal muscle myotubes, beating cardiac myocytes, osteoblasts, chondrocytes and macrophages) and signaling by Ras proteins. The expression of p204 in various tissues as promoted by tissue-specific transcription factors, its distribution among subcellular compartments, and the controls of these features are also discussed.

p204 protein overcomes the inhibition of the differentiation of P19 murine embryonal carcinoma cells to beating cardiac myocytes by Id proteins

We reported in the accompanying article (Ding, B., Liu, C., Huang, Y., Hickey, R. P., Yu, J., Kong, W., and Lengyel, P. (2006) J. Biol. Chem. 281, 14882-14892) that (i) the p204 protein is required for the differentiation of murine P19 embryonal carcinoma stem cells to beating cardiac myocytes, and (ii) the expression of p204 in the differentiating P19 cells is synergistically transactivated by the cardiac transcription factors Gata4, Nkx2.5, and Tbx5. Here we report that endogenous or ectopic inhibitor of differentiation (Id) proteins inhibited the differentiation of P19 cells to myocytes. This was in consequence of the binding of Id1, Id2, or Id3 protein to the Gata4 and Nkx2.5 proteins and the resulting inhibitions (i) of the binding of these transcription factors to each other and to DNA and (ii) of their synergistic transactivation of the expression of various genes, including atrial natriuretic factor and Ifi204 (encoding p204). p204 overcame this inhibition by Id proteins in consequence of (i) binding and sequestering Id proteins, (ii) accelerating their ubiquitination and degradation by proteasomes, and (iii) decreasing the level of Id proteins in the nucleus by increasing their translocation from the nucleus to the cytoplasm. Points (ii) and (iii) depended on the presence of the nuclear export signal in p204. In the course of the differentiation, Gata4, Nkx2.5, and p204 were components of a positive feedback loop. This loop arose in consequence of it that p204 overcame the inhibition of the synergistic activity of Gata4 and Nkx2.5 by the Id proteins.