Peroxiredoxin-6 Negatively Regulates Bactericidal Activity and NF-κB Activity by Interrupting TRAF6-ECSIT Complex

Abstract

A TRAF6-ECSIT complex is crucial for the generation of mitochondrial reactive oxygen species (mROS) and nuclear factor-kappa B (NF-κB) activation induced by Toll-like receptor 4 (TLR4). Peroxiredoxin-6 (Prdx6) as a member of the peroxiredoxin family of antioxidant enzymes is involved in antioxidant protection and cell signaling. Here, we report on a regulatory role of Prdx6 in mROS production and NF-κB activation by TLR4. Prdx6 was translocated into the mitochondria by TLR4 stimulation and Prdx6-knockdown (Prdx6KD) THP-1 cells had increased level of mitochondrial reactive oxygen species levels and were resistant to Salmonella typhimurium infection. Biochemical studies revealed Prdx6 interaction with the C-terminal TRAF-C domain of TRAF6, which drove translocation into the mitochondria. Interestingly, Prdx6 competitively interacted with ECSIT to TRAF6 through its C-terminal TRAF-C domain, leading to the interruption of TRAF6-ECSIT interaction. The inhibitory effect was critically implicated in the activation of NF-κB induced by TLR4. Overexpression of Prdx6 led to the inhibition of NF-κB induced by TLR4, whereas Prdx6KD THP-1 cells displayed enhanced production of pro-inflammatory cytokines including interleukin-6 and -1β, and the up-regulation of NF-κB-dependent genes induced by TLR4 stimulation. Taken together, the data demonstrate that Prdx6 interrupts the formation of TRAF6-ECSIT complex induced by TLR4 stimulation, leading to suppression of bactericidal activity because of inhibited mROS production in mitochondria and the inhibition of NF-κB activation in the cytoplasm.

Inhibition of TRAF6 ubiquitin-ligase activity by PRDX1 leads to inhibition of NFKB activation and autophagy activation

“…As shown in Figure 4 . Taken together, these results demonstrate that, upon TLR stimulation, TRAF6 is auto-ubiquitinated at its K124 residue with simultaneous ubiquitination of ECSIT protein (Figure 4(e), left) [22][23][24][25][26]. The complex is further associated with TAB1 and TAB2 proteins to facilitate the activation of MAP3K7, leading to the activation of NFKB [24,26,27].…”

“…We next explored the molecular mechanism by which PRDX1 negatively regulated TLR4-mediated signaling. Our recent studies have revealed that PRDX6 (peroxiredoxin 6) interrupts the formation of TRAF6-ECSIT complex which plays a key role in the activation of NFKB induced by TLR4 stimulation through molecular interaction between TRAF6 and PRDX6 [22][23][24][25]. Therefore, we hypothesized that PRDX1 also could affect the formation of TRAF6-ECSIT complex.…”

“…Autophagy is critically associated with bacterial elimination in infectious diseases [28] and cancer progression [29][30][31][32][33][34]. TRAF6 is functionally implicated in bactericidal activity through regulation of mitochondrial reactive oxygen species (mROS) [25,35] and autophagy activation through ubiquitination of BECN1 [10]. We therefore investigated whether PRDX1 was functionally associated with bactericidal activity and cancer progression through inhibition of TRAF6 ubiquitin-ligase activity.…”

TNF receptor associated factor 6 interacts with ALS-linked misfolded superoxide dismutase 1 and promotes aggregation

“…TRAF6 is a cytoplasmic-localized RING-type ubiquitin ligase classically known for its role in the canonical nuclear factor kappa-B (NF-κB) signaling pathway, where it participates in the transduction of signals downstream of a multitude of immunoregulatory receptors (23)(24)(25)(26) and functions as a hub protein in the crosstalk of immune-regulatory pathways with the autophagy machinery (27)(28)(29)(30). TRAF6 is not strictly localized to the cytoplasm but translocates to mitochondria in certain contexts (31)(32)(33)(34)(35). Importantly, TRAF6 has been previously implicated in neurodegenerative diseases, including Parkinson's disease (36)(37)(38), Huntington's disease (39), and Alzheimer's disease (40)(41)(42), where it stimulates the ubiquitination of disease-associated proteins and exerts a regulatory role on their turnover and aggregation (43).…”

“…The RING domain and adjacent zinc finger motifs are involved in E2 ubiquitin conjugase binding and are required for TRAF6 function as an E3 ubiquitin ligase (50). The MATH domain is an eight-stranded anti-parallel β -sandwich with which TRAF6 engages in a multitude of protein-protein interactions (32,(51)(52)(53). To determine the domain of TRAF6 that interacts with mutant SOD1, two TRAF6 deletion constructs were generated: TRAF6 ∆ C (aa.…”