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Peli1 facilitates TRIF-dependent Toll-like receptor signaling and proinflammatory cytokine production.

Chang M, Jin W, Sun SC - Nat. Immunol. (2009)

Bottom Line: Peli1 was required for TLR3-induced activation of IkappaB kinase (IKK) and its 'downstream' target, transcription factor NF-kappaB, but was dispensable for IKK-NF-kappaB activation induced by several other TLRs and the interleukin 1 (IL-1) receptor.Notably, Peli1 bound to and ubiquitinated RIP1, a signaling molecule that mediates IKK activation induced by the TLR3 and TLR4 adaptor TRIF.Our findings suggest that Peli1 is a ubiquitin ligase needed for the transmission of TRIF-dependent TLR signals.

View Article: PubMed Central - PubMed

Affiliation: Department of Immunology, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA.

ABSTRACT
Toll-like receptors (TLRs) are pivotal in innate immunity and inflammation. Here we show that genetic deficiency in Peli1, an E3 ubiquitin ligase, attenuated the induction of proinflammatory cytokines by ligands of TLR3 and TLR4 and rendered mice resistant to septic shock. Peli1 was required for TLR3-induced activation of IkappaB kinase (IKK) and its 'downstream' target, transcription factor NF-kappaB, but was dispensable for IKK-NF-kappaB activation induced by several other TLRs and the interleukin 1 (IL-1) receptor. Notably, Peli1 bound to and ubiquitinated RIP1, a signaling molecule that mediates IKK activation induced by the TLR3 and TLR4 adaptor TRIF. Our findings suggest that Peli1 is a ubiquitin ligase needed for the transmission of TRIF-dependent TLR signals.

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Dispensable role of Peli1 in IL-1R signaling(a) Peli1+/+ and Peli1−/− MEFs were stimulated with IL-1β (10 ng/ml) and subjected to real-time RT-PCR. Data are presented as fold induction (mean ± sd) over the non-stimulated (0 h) Peli1+/+ samples. (b) Peli1+/+ and Peli1−/− mice were injected (i.p.) with IL-1β (20 μg/kg body weight) and bled at 2 h after the injection. The concentration of IL-6 and TNF was determined by ELISA and presented as mean ± sd (n = 5 mice of each genotype). TNF was undetectable at 30 min and 2 h (data not shown). (c,d) MEFs were not treated (NT) or stimulated with IL-1β Nuclear extracts were subjected to EMSA using NF-κB or NF-Y probes (c), and total cell lysates were subjected to in vitro kinase assays using GST-IκBα(1-54) as substrate (d). Data are representative of 2 (a,b) and 3 (c,d) independent experiments.
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Figure 5: Dispensable role of Peli1 in IL-1R signaling(a) Peli1+/+ and Peli1−/− MEFs were stimulated with IL-1β (10 ng/ml) and subjected to real-time RT-PCR. Data are presented as fold induction (mean ± sd) over the non-stimulated (0 h) Peli1+/+ samples. (b) Peli1+/+ and Peli1−/− mice were injected (i.p.) with IL-1β (20 μg/kg body weight) and bled at 2 h after the injection. The concentration of IL-6 and TNF was determined by ELISA and presented as mean ± sd (n = 5 mice of each genotype). TNF was undetectable at 30 min and 2 h (data not shown). (c,d) MEFs were not treated (NT) or stimulated with IL-1β Nuclear extracts were subjected to EMSA using NF-κB or NF-Y probes (c), and total cell lysates were subjected to in vitro kinase assays using GST-IκBα(1-54) as substrate (d). Data are representative of 2 (a,b) and 3 (c,d) independent experiments.

Mentions: Prior transfection studies performed using a cell line model suggest that Peli1 facilitates IL-1R signaling 34. However, it is unknown whether Peli1 is required for IL-1R signaling under physiological conditions. To address this question, we examined the effect of Peli1 deficiency on IL-1R-mediated pro-inflammatory gene induction in primary MEFs, a cell type that efficiently responds to IL-1β stimulation. In Peli1+/+ MEFs, IL-1β stimulated the expression of Tnf and Il6, although it did not induce appreciable expression of IL-12p40 (Fig. 5a and data not shown). IL-1β also induced expression of Cxcl10, the gene encoding IP-10, in Peli1+/+ MEFs. However, loss of Peli1 did not affect IL-1β-stimulated expression of Tnf, Il6 or Cxcl10 (Fig. 5a). To further examine the role of Peli1 in IL-1R signaling, we employed an in vivo gene induction model. When injected into Peli1+/+ mice, IL-1β stimulated production of high concentrations of IL-6 (Fig. 5b), although it did not induce detectable quantities of TNF (data not shown). Consistent with the in vitro results, Peli1 was completely dispensable for IL-1β-induced IL-6 production in vivo (Fig. 5b).


Peli1 facilitates TRIF-dependent Toll-like receptor signaling and proinflammatory cytokine production.

Chang M, Jin W, Sun SC - Nat. Immunol. (2009)

Dispensable role of Peli1 in IL-1R signaling(a) Peli1+/+ and Peli1−/− MEFs were stimulated with IL-1β (10 ng/ml) and subjected to real-time RT-PCR. Data are presented as fold induction (mean ± sd) over the non-stimulated (0 h) Peli1+/+ samples. (b) Peli1+/+ and Peli1−/− mice were injected (i.p.) with IL-1β (20 μg/kg body weight) and bled at 2 h after the injection. The concentration of IL-6 and TNF was determined by ELISA and presented as mean ± sd (n = 5 mice of each genotype). TNF was undetectable at 30 min and 2 h (data not shown). (c,d) MEFs were not treated (NT) or stimulated with IL-1β Nuclear extracts were subjected to EMSA using NF-κB or NF-Y probes (c), and total cell lysates were subjected to in vitro kinase assays using GST-IκBα(1-54) as substrate (d). Data are representative of 2 (a,b) and 3 (c,d) independent experiments.
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Figure 5: Dispensable role of Peli1 in IL-1R signaling(a) Peli1+/+ and Peli1−/− MEFs were stimulated with IL-1β (10 ng/ml) and subjected to real-time RT-PCR. Data are presented as fold induction (mean ± sd) over the non-stimulated (0 h) Peli1+/+ samples. (b) Peli1+/+ and Peli1−/− mice were injected (i.p.) with IL-1β (20 μg/kg body weight) and bled at 2 h after the injection. The concentration of IL-6 and TNF was determined by ELISA and presented as mean ± sd (n = 5 mice of each genotype). TNF was undetectable at 30 min and 2 h (data not shown). (c,d) MEFs were not treated (NT) or stimulated with IL-1β Nuclear extracts were subjected to EMSA using NF-κB or NF-Y probes (c), and total cell lysates were subjected to in vitro kinase assays using GST-IκBα(1-54) as substrate (d). Data are representative of 2 (a,b) and 3 (c,d) independent experiments.
Mentions: Prior transfection studies performed using a cell line model suggest that Peli1 facilitates IL-1R signaling 34. However, it is unknown whether Peli1 is required for IL-1R signaling under physiological conditions. To address this question, we examined the effect of Peli1 deficiency on IL-1R-mediated pro-inflammatory gene induction in primary MEFs, a cell type that efficiently responds to IL-1β stimulation. In Peli1+/+ MEFs, IL-1β stimulated the expression of Tnf and Il6, although it did not induce appreciable expression of IL-12p40 (Fig. 5a and data not shown). IL-1β also induced expression of Cxcl10, the gene encoding IP-10, in Peli1+/+ MEFs. However, loss of Peli1 did not affect IL-1β-stimulated expression of Tnf, Il6 or Cxcl10 (Fig. 5a). To further examine the role of Peli1 in IL-1R signaling, we employed an in vivo gene induction model. When injected into Peli1+/+ mice, IL-1β stimulated production of high concentrations of IL-6 (Fig. 5b), although it did not induce detectable quantities of TNF (data not shown). Consistent with the in vitro results, Peli1 was completely dispensable for IL-1β-induced IL-6 production in vivo (Fig. 5b).

Bottom Line: Peli1 was required for TLR3-induced activation of IkappaB kinase (IKK) and its 'downstream' target, transcription factor NF-kappaB, but was dispensable for IKK-NF-kappaB activation induced by several other TLRs and the interleukin 1 (IL-1) receptor.Notably, Peli1 bound to and ubiquitinated RIP1, a signaling molecule that mediates IKK activation induced by the TLR3 and TLR4 adaptor TRIF.Our findings suggest that Peli1 is a ubiquitin ligase needed for the transmission of TRIF-dependent TLR signals.

View Article: PubMed Central - PubMed

Affiliation: Department of Immunology, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA.

ABSTRACT
Toll-like receptors (TLRs) are pivotal in innate immunity and inflammation. Here we show that genetic deficiency in Peli1, an E3 ubiquitin ligase, attenuated the induction of proinflammatory cytokines by ligands of TLR3 and TLR4 and rendered mice resistant to septic shock. Peli1 was required for TLR3-induced activation of IkappaB kinase (IKK) and its 'downstream' target, transcription factor NF-kappaB, but was dispensable for IKK-NF-kappaB activation induced by several other TLRs and the interleukin 1 (IL-1) receptor. Notably, Peli1 bound to and ubiquitinated RIP1, a signaling molecule that mediates IKK activation induced by the TLR3 and TLR4 adaptor TRIF. Our findings suggest that Peli1 is a ubiquitin ligase needed for the transmission of TRIF-dependent TLR signals.

Show MeSH
Related in: MedlinePlus