The proinflammatory cytokine interleukin-1 (IL-1) signals via type I IL-1 receptor (IL-1RI) and IL-1 receptor accessory protein (IL1RAP), which leads to activation of the transcription factor NF-κB and induction of a range of downstream proteins involved in inflammatory and immune responses. Here, we identified the E3 ubiquitin ligase membrane-associated RING-CH (MARCH8) as a suppressor of IL-1β-induced NF-κB-and MAPK-activation pathways. Overexpression of MARCH8 inhibits IL-1β-induced NF-κB and MAPK activation, whereas knockdown of MARCH8 has the opposite effect. Mechanistically, MARCH8 interacts with IL1RAP and targets its Lys512 for K48-linked polyubiquitination and degradation. Our findings suggest that MARCH8-mediated polyubiquitination and degradation of IL1RAP is an important mechanism for negative regulation of IL-1β-induced signaling pathways.T he transcription factor NF-κB plays pivotal roles in many aspects of cellular processes such as inflammation, innate immunity, and cancer. NF-κB is sequestered in the cytoplasm and kept inactive in nonstimulated cells by binding to inhibitory IκB (inhibitor of κB) proteins. Under stimulation with cytokines, infectious pathogens, or genotoxic stresses, the IκB proteins are phosphorylated, ubiquitinated, and ultimately degraded, which frees NF-κB for translocation into the nucleus, where it induces transcription of downstream target genes (1-3).Interleukin 1 (IL-1) is a critical proinflammatory cytokine that can trigger a cascade of signaling leading to activation of NF-κB. It functions through engagement of two membrane-bound receptors: IL-1 receptor type I (IL-1RI) and IL-1 receptor accessory protein (IL1RAP) (4-6). IL-1RI is the ligand-recognition receptor that binds IL-1β directly (7). Although IL1RAP does not bind IL-1β directly, its recruitment to IL-1RI following IL-1β stimulation is essential for the formation of an activated membrane receptor complex (8-10). The activated complex can then recruit intracellular adaptor proteins and kinases, including MyD88, IRAK4,. IRAK4 phosphorylates and activates IRAK1, which in turn recruits TRAF6. IRAK1 and TRAF6 form a complex that is released from the receptor complex (15, 16). TRAF6 possesses an E3 ubiquitin ligase activity that mediates its autoubiquitination. Ubiquitinated TRAF6 further recruits the TGF-b-activated kinase 1 (TAK1)-TAK1-binding protein 2 (TAB2)-TAB3 complex, resulting in the activation of TAK1. Activated TAK1 subsequently activates downstream kinases IKK-α and IKK-β, which phosphorylate IκB proteins, and lead to activation of NF-κB (17).Several studies have suggested that ubiquitination is a central rhythm of regulation of IL-1β-induced NF-κB activation pathways. It has been shown that the E3 ubiquitin ligase TRAF6 mediates K63-linked polyubiquitination of IRAK1 for recruiting IKK and activating NF-κB (18). Tripartite motif 8 (TRIM8) catalyzes K63-linked polyubiquitination of TAK1, and this promotes the activation of TAK1 (19). It has also been demonstrated that the E3 ligase Pellino 3b acts as a n...

The glycophosphatidylinositol (GPI) anchors of proteins expressed on human erythrocytes and nucleated cells differ with respect to acylation of an inositol hydroxyl group, a structural feature that modulates their cleavability by PI-specific phospholipase C (PI-PLC). To determine how this GPI anchor modification is regulated, the precursor and protein-associated GPIs in two K562 cell transfectants (ATCC and .48) exhibiting alternatively PI-PLC-sensitive and resistant surface proteins were analyzed and the temporal relationship between GPI protein transfer and acquisition of PI-PLC sensitivity was determined. Nondenaturing PAGE analyses demonstrated that, whereas in .48 transfectants the GPI anchors in decay accelerating factor (DAF) and placental alkaline phosphatase (PLAP) were >95% acylated, in ATCC transfectants, they were 60 and 33% unsubstituted, respectively. In contrast, TLC analyses revealed that putative GPI donors in the two lines were identical and were >95% acylated. Studies of de novo DAF biosynthesis in HeLa cells bearing proteins with >90% unacylated anchors showed that within 5 min at 37°C (or at 18°C, which does not permit endoplasmic reticilum exit), >50% of the anchor in nascent 44-kDa proDAF protein exhibited PI-PLC sensitivity. In vitro analyses of the microsomal processing of miniPLAP, a truncated PLAP reporter protein, demonstrated that the anchor donor initially transferred to prominiPLAP was acylated and then progressively was deacylated. These findings indicate that (i) the anchor moiety that initially transfers to nascent proteins is acylated, (ii) inositol acylation in mature surface proteins is regulated via posttransfer deacylation, which in general is cell-specific but also can be proteindependent, and (iii) deacylation occurs in the endoplasmic reticulum immediately after GPI transfer.

Unraveling the essence of hydrogen adsorption and desorption behaviors can fundamentally guide catalyst design and promote catalytic performance. Herein, the regulation of hydrogen adsorption is systematically investigated by d–d orbital interaction of metallic tungsten dioxide (WO2). Theoretical simulations show that the incorporation of post‐transition metal atoms including Fe, Co, Ni, and Cu can gradually reduce the bond order of W—M sites, consequently weakening the hydrogen adsorption and accelerating the hydrogen evolution reaction (HER) process. Under that theoretical guidance, various 3d metal doped WO2 electrocatalysts are systematically screened for HER catalysis. Among them, the Ni‐WO2/nickel foam exhibits an overpotential of 41 mV (−10 mA cm−2) and Tafel slope down to 47 mV dec−1 representing the best tungsten‐based HER catalysts so far. This work demonstrates that optimizing hydrogen adsorption via d–d orbital modulation is an effective approach to developing efficient and robust catalysts.