HDAC6 mediates an aggresome-like mechanism for NLRP3 and pyrin inflammasome activation.

Inflammasomes are supramolecular complexes that play key roles in immune surveillance. This is accomplished by the activation of inflammatory caspases, which leads to the proteolytic maturation of interleukin 1β (IL-1β) and pyroptosis. Here, we show that nucleotide-binding domain, leucine-rich repeat, and pyrin domain-containing protein 3 (NLRP3)- and pyrin-mediated inflammasome assembly, caspase activation, and IL-1β conversion occur at the microtubule-organizing center (MTOC).

The NLRP3 inflammasome: Mechanism of action, role in disease and therapies.

NLRP3 is the best characterized cytosolic nod-like pattern recognition receptor which can detect microbial motifs, endogenous danger and stress signals. Activation of NLRP3 leads to the formation of a cytosolic multiprotein signaling complex called the inflammasome, which serves as a platform for caspase-1 activation leading to the processing of proinflammatory cytokines IL-1β, IL-18 and GSDMD mediated cell death. This form of pyroptotic cell death represents a major pathway of inflammation.

Structural mechanism for NEK7-licensed activation of NLRP3 inflammasome.

The NLRP3 inflammasome can be activated by stimuli that include nigericin, uric acid crystals, amyloid-β fibrils and extracellular ATP. The mitotic kinase NEK7 licenses the assembly and activation of the NLRP3 inflammasome in interphase. Here we report a cryo-electron microscopy structure of inactive human NLRP3 in complex with NEK7, at a resolution of 3.

K63-linked polyubiquitin chains bind to DNA to facilitate DNA damage repair.

Polyubiquitylation is canonically viewed as a posttranslational modification that governs protein stability or protein-protein interactions, in which distinct polyubiquitin linkages ultimately determine the fate of modified protein(s). We explored whether polyubiquitin chains have any nonprotein-related function. Using in vitro pull-down assays with synthetic materials, we found that polyubiquitin chains with the Lys (K63) linkage bound to DNA through a motif we called the "DNA-interacting patch" (DIP), which is composed of the adjacent residues Thr, Lys, and Glu Upon DNA damage, the binding of K63-linked polyubiquitin chains to DNA enhanced the recruitment of repair factors through their interaction with an Ile patch in ubiquitin to facilitate DNA repair.

Evidence for M1-Linked Polyubiquitin-Mediated Conformational Change in NEMO.

The NF-κB essential modulator (NEMO) is the scaffolding subunit of the inhibitor of κB kinase (IKK) holocomplex and is required for the activation of the catalytic IKK subunits, IKKα and IKKβ, during the canonical inflammatory response. Although structures of shorter constructs of NEMO have been solved, efforts to elucidate the full-length structure of NEMO have proved difficult due to its apparent high conformational plasticity. To better characterize the gross dimensions of full-length NEMO, we employed in-line size exclusion chromatography-small-angle X-ray scattering.

The hierarchical structural architecture of inflammasomes, supramolecular inflammatory machines.

Inflammasomes are caspase-1 activating, molecular inflammatory machines that proteolytically mature pro-inflammatory cytokines and induce pyroptotic cell death during innate immune responses. Recent structural studies of proteins that constitute inflammasomes have yielded fresh insights into their assembly mechanisms. In particular, these include a crystal structure of the CARD-containing NOD-like receptor NLRC4, the crystallographic and electron microscopy (EM) studies of the dsDNA sensors AIM2 and IFI16, and of the regulatory protein p202, and the cryo-EM filament structure of the PYD domain of the inflammasome adapter ASC.

Probing kinase activation and substrate specificity with an engineered monomeric IKK2.

Catalytic subunits of the IκB kinase (IKK), IKK1/IKKα, and IKK2/IKKβ function in vivo as dimers in association with the necessary scaffolding subunit NEMO/IKKγ. Recent X-ray crystal structures of IKK2 suggested that dimerization might be mediated by a smaller protein-protein interaction than previously thought. Here, we report that removal of a portion of the scaffold dimerization domain (SDD) of human IKK2 yields a kinase subunit that remains monomeric in solution.

A structural basis for IκB kinase 2 activation via oligomerization-dependent trans auto-phosphorylation.

Activation of the IκB kinase (IKK) is central to NF-κB signaling. However, the precise activation mechanism by which catalytic IKK subunits gain the ability to induce NF-κB transcriptional activity is not well understood. Here we report a 4 Å x-ray crystal structure of human IKK2 (hIKK2) in its catalytically active conformation.

X-ray crystal structure of the UCS domain-containing UNC-45 myosin chaperone from Drosophila melanogaster.

UCS proteins, such as UNC-45, influence muscle contraction and other myosin-dependent motile processes. We report the first X-ray crystal structure of a UCS domain-containing protein, the UNC-45 myosin chaperone from Drosophila melanogaster (DmUNC-45). The structure reveals that the central and UCS domains form a contiguous arrangement of 17 consecutive helical layers that arrange themselves into five discrete armadillo repeat subdomains.