NLRP3 is an important pattern recognition receptor involved in mediating inflammasome activation in response to viral and bacterial infections as well as various proinflammatory stimuli associated with tissue damage or malfunction. Upon activation, NLRP3 assembles a multimeric inflammasome complex comprising the adaptor ASC and the effector pro-caspase-1 to mediate the activation of caspase-1. Although NLRP3 expression is induced by the NF-κB pathway, the posttranscriptional molecular mechanism controlling the activation of NLRP3 remains elusive. Using both pharmacological and molecular approaches, we show that the activation of NLRP3 inflammasome is regulated by a deubiquitination mechanism. We further identify the deubiquitinating enzyme, BRCC3, as a critical regulator of NLRP3 activity by promoting its deubiquitination and characterizing NLRP3 as a substrate for the cytosolic BRCC3-containing BRISC complex. Our results elucidate a regulatory mechanism involving BRCC3-dependent NLRP3 regulation and highlight NLRP3 ubiquitination as a potential therapeutic target for inflammatory diseases.

It has recently been hypothesized that hepatocyte CHO metabolites (hexose-or triose-phosphates) might not only stimulate ChREBP and activate DNL, but might also serve as a signal to enhance HGP (17,18). This hypothesis derives in part from the counterintuitive observation that while ChREBP is known to stimulate glycolysis through transactivation of glycolytic genes (22), it may also transactivate expression of G6pc encoding the enzyme er, from skeletal muscle and adipose tissue enhances hepatic DNL (20). Additionally, siRNA-mediated knockdown of ChREBP in ob/ob mice decreases hepatic DNL in the setting of persistent hyperinsulinemia (21). Thus, hepatic DNL may be regulated by increased substrate delivery independently of insulin signaling. However, whether increasing intrahepatic CHO metabolites might also signal to increase glucose production has not been fully explored.

No abstract

Cochlin, an extracellular matrix protein, shares homologies with the Factor C, a serine protease found in horseshoe crabs, which is critical for anti-bacterial responses. Mutations in the COCH gene are responsible for human DFNA9 syndrome, a disorder characterized by neurodegeneration of inner ear that leads to hearing loss and vestibular impairments. The physiological function of cochlin, however, is unknown. Here, we report that cochlin is specifically expressed by follicular dendritic cells, and selectively localized in the fine extracellular network of conduits in the spleen and lymph nodes. During inflammation, cochlin was cleaved by aggrecanases and secreted into blood circulation. In models of lung infection with Pseudomonas aeruginosa and Staphylococcus aureus, Coch−/− mice show reduced survival linked to defects in local cytokine production, recruitment of immune effector cells and bacterial clearance. By producing cochlin, FDCs thus contribute to the innate immune response in defense against bacteria.

No abstract