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  • 1
    Publication Date: 2016-01-28
    Description: Inflammasomes are intracellular protein complexes that drive the activation of inflammatory caspases. So far, four inflammasomes involving NLRP1, NLRP3, NLRC4 and AIM2 have been described that recruit the common adaptor protein ASC to activate caspase-1, leading to the secretion of mature IL-1beta and IL-18 proteins. The NLRP3 inflammasome has been implicated in the pathogenesis of several acquired inflammatory diseases as well as cryopyrin-associated periodic fever syndromes (CAPS) caused by inherited NLRP3 mutations. Potassium efflux is a common step that is essential for NLRP3 inflammasome activation induced by many stimuli. Despite extensive investigation, the molecular mechanism leading to NLRP3 activation in response to potassium efflux remains unknown. Here we report the identification of NEK7, a member of the family of mammalian NIMA-related kinases (NEK proteins), as an NLRP3-binding protein that acts downstream of potassium efflux to regulate NLRP3 oligomerization and activation. In the absence of NEK7, caspase-1 activation and IL-1beta release were abrogated in response to signals that activate NLRP3, but not NLRC4 or AIM2 inflammasomes. NLRP3-activating stimuli promoted the NLRP3-NEK7 interaction in a process that was dependent on potassium efflux. NLRP3 associated with the catalytic domain of NEK7, but the catalytic activity of NEK7 was shown to be dispensable for activation of the NLRP3 inflammasome. Activated macrophages formed a high-molecular-mass NLRP3-NEK7 complex, which, along with ASC oligomerization and ASC speck formation, was abrogated in the absence of NEK7. NEK7 was required for macrophages containing the CAPS-associated NLRP3(R258W) activating mutation to activate caspase-1. Mouse chimaeras reconstituted with wild-type, Nek7(-/-) or Nlrp3(-/-) haematopoietic cells showed that NEK7 was required for NLRP3 inflammasome activation in vivo. These studies demonstrate that NEK7 is an essential protein that acts downstream of potassium efflux to mediate NLRP3 inflammasome assembly and activation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉He, Yuan -- Zeng, Melody Y -- Yang, Dahai -- Motro, Benny -- Nunez, Gabriel -- R01AI063331/AI/NIAID NIH HHS/ -- R01DK091191/DK/NIDDK NIH HHS/ -- T32 HL007517/HL/NHLBI NIH HHS/ -- T32DK094775/DK/NIDDK NIH HHS/ -- T32HL007517/HL/NHLBI NIH HHS/ -- England -- Nature. 2016 Feb 18;530(7590):354-7. doi: 10.1038/nature16959. Epub 2016 Jan 27.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Pathology and Comprehensive Cancer Center, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA. ; The State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China. ; The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900, Israel.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26814970" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Apoptosis Regulatory Proteins/deficiency/genetics/metabolism ; Biocatalysis ; Carrier Proteins/chemistry/genetics/*metabolism ; Caspase 1/metabolism ; Catalytic Domain ; Cells, Cultured ; Cryopyrin-Associated Periodic Syndromes/genetics ; Enzyme Activation ; HEK293 Cells ; Humans ; Inflammasomes/*chemistry/*metabolism ; Interleukin-1beta/secretion ; Macrophages/metabolism ; Mice ; Mice, Inbred C57BL ; Potassium/*metabolism ; Protein Binding ; Protein Multimerization ; Protein-Serine-Threonine Kinases/chemistry/deficiency/genetics/*metabolism
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
    ISSN: 0040-4020
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2018-05-25
    Description: The phagocyte reduced NAD phosphate (NADPH) oxidase generates superoxide, the precursor to reactive oxygen species (ROS) that has both antimicrobial and immunoregulatory functions. Inactivating mutations in NADPH oxidase alleles cause chronic granulomatous disease (CGD), characterized by enhanced susceptibility to life-threatening microbial infections and inflammatory disorders; hypomorphic NADPH oxidase alleles are associated with autoimmunity. Impaired apoptotic cell (AC) clearance is implicated as an important contributing factor in chronic inflammation and autoimmunity, but the role of NADPH oxidase–derived ROS in this process is incompletely understood. Here, we demonstrate that phagocytosis of AC (efferocytosis) potently activated NADPH oxidase in mouse peritoneal exudate macrophages (PEMs). ROS generation was dependent on macrophage CD11b, Toll-like receptor 2 (TLR2), TLR4, and myeloid differentiation primary response 88 (MyD88), and was also regulated by phosphatidylinositol 3-phosphate binding to the p40 phox oxidase subunit. Maturation of efferosomes containing apoptotic neutrophils was significantly delayed in CGD PEMs, including acidification and acquisition of proteolytic activity, and was associated with slower digestion of apoptotic neutrophil proteins. Treatment of wild-type macrophages with the vacuolar-type H+ ATPase inhibitor bafilomycin also delayed proteolysis within efferosomes, showing that luminal acidification was essential for efficient digestion of efferosome proteins. Finally, cross-presentation of AC-associated antigens by CGD PEMs to CD8 T cells was increased. These studies unravel a key role for the NADPH oxidase in the disposal of ACs by inflammatory macrophages. The oxidants generated promote efferosome maturation and acidification that facilitate the degradation of ingested ACs.
    Keywords: Phagocytes, Granulocytes, and Myelopoiesis
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
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