RelB suppresses type I Interferon signaling in dendritic cells.

Type I Interferon (IFN) signaling plays a critical role in dendritic cell (DC) development and functions. Inhibition of hyper type I IFN signaling promotes cDC2 subtype development. Relb is essential to development of cDC2 subtype and here we analyzed its effect on type I IFN signaling in DCs. We show that Relb suppresses the homeostatic type I IFN signaling in cDC2 cultures. TLR stimulation of FL-DCs led to RelB induction coinciding with fall in IFN signatures; conforming with the observation Relb expression reduced TLR stimulated IFN induction along with decrease in ISGs. Towards understanding mechanism, we show that effects of RelB are mediated by increased levels of IκBα. We demonstrate that RelB dampened antiviral responses by lowering ISG levels and the defect in cDC2 development in RelB null mice can be rescued in Ifnar1-/- background. Overall, we propose a novel role of RelB as a negative regulator of the type I IFN signaling pathway; fine tuning development of cDC2 subtype.

MST4 modulates the neuro-inflammatory response by regulating IκBα signaling pathway and affects the early outcome of experimental ischemic stroke in mice.

MST4 limits peripheral, macrophage-dependent inflammatory responses through direct phosphorylation of the adaptor TRAF6; though its role in neuro-inflammation is unclear. We investigated microglia expression of MST4 and whether is attenuates neuro-inflammatory response after cerebral ischemia-reperfusion injury in mice. Adult male C57BL6 mice were subjected to a 90-minute middle cerebral artery occlusion (MCAO) followed by a 72 -h reperfusing. The results showed that MST4 was involved in the pathological process after cerebral ischemia-reperfusion and was expressed in microglia. MST4-Adeno Associated Virus attenuated brain damage after MCAO and reduced expression of p-IκBα, p-ERK and p-JNK, while MST4 shRNA aggravated brain damage after MCAO and increased expression of p-IκBα, p-ERK and p-JNK. Our results show that MST4 inhibits neuro-inflammatory response in cerebral ischemia-reperfusion injury, improves neurological deficits, and reduces cerebral infarction volume in mice. Strategies to enhance MST4 in response to ischemic stroke may be a potential therapeutic strategy.

The neuroprotective effect of schisandrol A on 6-OHDA-induced PD mice may be related to PI3K/AKT and IKK/IκBα/NF-κB pathway.

Parkinson's disease is the second most common neurodegenerative disease. Its main pathological feature is the substantial nigra-striatum dopaminergic neuronal dysfunction, which causes insufficient release of DA, induces motor symptoms, and is accompanied by nonmotor symptoms. Schisandrol A belongs to lignan components and has anti-inflammatory, antioxidant and neuroprotective effects. In this experiment, we injected 6-OHDA into medial forebrain bundle of C57BL/6J male mice to establish the model. The motor function of mice was examined by open field test and pole test, the depression-like behavior of mice was examined by sucrose preference test and the memory function was examined by Y maze. We found that schisandrol A (20 mg/kg/d) could significantly improve the motor symptoms, and alleviate the depression-like symptoms and memory dysfunction of PD mice induced by 6-OHDA. Then we studied the neuroprotective mechanism of schisandrol A by H.E., ELISA assay kits and Western blot. Results showed that schisandrol A may enhance the PI3K/AKT pathway, inhibit the IKK/IκBα/NF-κB pathway, reduce neuronal inflammation and oxidative stress, and enhance the survival of DA neurons in the brain of mice. These results indicate that schisandrol A is expected to be a potential drug for improving Parkinson's disease.

Development of mKO2 fusion proteins for real-time imaging and mechanistic investigation of the degradation kinetics of human IκBα in living cells.

In resting cells, the nuclear factor kappa B (NF-κB) family of transcription factors is stabilized by complexation with the cytoplasmic inhibitor of kappa B alpha (IκBα). Extracellular stimuli, such as tumor necrosis factor alpha (TNFα) or bacterial lipopolysaccharide activate NF-κB through IκBα phosphorylation and ubiquitin-proteasomal degradation. Herein, we developed a novel biosensor, by fusing the monomeric fluorescent protein Kusabira-Orange 2 to IκBα (mKO2-IκBα), to study the dynamics and structure-activity relationship of IκBα degradation. Site-specific deletion studies on the IκBα sequence revealed that the C-terminal PEST domain is required in signal-induced proteasomal degradation of IκBα and functions independently from ankyrin repeats. Using deletion mutants, we show that IκBα ankyrin repeats do not affect IκBα degradability but affect its degradation rate. We demonstrate, by both real-time confocal microscopy and western blot analysis, that the half-life of mKO2-IκBα in response to TNFα is approximately 35 min, which is similar to the half-life of endogenous IκBα. Using this biosensor we also show that selective proteasome inhibitors, such as lactacystin and MG132, inhibit degradation and affect the kinetics of IκBα in a dose-dependent manner. The techniques described here can have a range of possible applications, such as facilitating studies associated with IκBα dynamics and biochemical characteristics, as well as the screening of potential proteasome inhibitors.

Blockade of deubiquitinase USP7 overcomes bortezomib resistance by suppressing NF-κB signaling pathway in multiple myeloma.

The treatment of multiple myeloma (MM) with bortezomib (BTZ) is promising; however, the emergence of resistance is challenging in the clinical treatment. Thus, a novel targeted treatment or exploring the mechanism underlying BTZ resistance is an urgent requisite. The current data showed that high expression of USP7 in myeloma was a predictor of short overall survival and poor outcome. USP7 knockout significantly suppressed the colony formation, inhibited the proliferation of BTZ-resistant MM cells even in the presence of growth factors, and overcame BTZ resistance. The knockout markedly inhibited the tumor growth and prolonged the survival of mice bearing BTZ-resistant MM cells. Mechanistically, USP7 knockout remarkably increased the sensitivity to BTZ by stabilizing ΙκΒα and blocking the NF-κB pathway. Not surprisingly, when IκBα was knocked down by siRNA transfection, the MM cells restored the BTZ resistance. Importantly, usage of USP7 inhibitors also suppressed the activation of NF-κB and combination with BTZ triggered the synergistic antitumor activity in BTZ-resistant MM cells. Taken together, this study provides the rationale for clinical protocols evaluating USP7 inhibition, alone and in combination with BTZ, to overcome BTZ resistance and improve the patient outcome in MM.