title: Myeloid-Specific Gene Deletion of Protein Phosphatase 2A Magnifies MyD88- and TRIF-Dependent Inflammation following Endotoxin Challenge.
abstract: Protein phosphatase 2A (PP2A) is a member of the intracellular serine/threonine phosphatases. Innate immune cell activation triggered by pathogen-associated molecular patterns is mediated by various protein kinases, and PP2A plays a counter-regulatory role by deactivating these kinases. In this study, we generated a conditional knockout of the α isoform of the catalytic subunit of PP2A (PP2ACα). After crossing with myeloid-specific cre-expressing mice, effective gene knockout was achieved in various myeloid cells. The myeloid-specific knockout mice (lyM-PP2Afl/fl) showed higher mortality in response to endotoxin challenge and bacterial infection. Upon LPS challenge, serum levels of TNF-α, KC, IL-6, and IL-10 were significantly increased in lyM-PP2Afl/flmice, and increased phosphorylation was observed in MAPK pathways (p38, ERK, JNK) and the NF-κB pathway (IKKα/β, NF-κB p65) in bone marrow-derived macrophages (BMDMs) from knockout mice. Heightened NF-κB activation was not associated with degradation of IκBα; instead, enhanced phosphorylation of the NF-κB p65 subunit and p38 phosphorylation-mediated TNF-α mRNA stabilization appear to contribute to the increased TNF-α expression. In addition, increased IL-10 expression appears to be due to PP2ACα-knockout-induced IKKα/β hyperactivation. Microarray experiments indicated that the Toll/IL-1R domain-containing adaptor inducing IFN-β/ TNFR-associated factor 3 pathway was highly upregulated in LPS-treated PP2ACα-knockout BMDMs, and knockout BMDMs had elevated IFN-α/β production compared with control BMDMs. Serum IFN-β levels from PP2ACα-knockout mice treated with LPS were also greater than those in controls. Thus, we demonstrate that PP2A plays an important role in regulating inflammation and survival in the setting of septic insult by targeting MyD88- and Toll/IL-1R domain-containing adaptor inducing IFN-β-dependent pathways.
authors.affiliation: Division of Critical Care Medicine, Department of Pediatrics and Communicable Diseases, University of Michigan Medical School, Ann Arbor, MI 48109; leisun@med.umich.edu.
authors.forename: Lei
authors.identifier: 0000-0002-7804-0876
authors.initials: L
authors.lastname: Sun
authors.affiliation: Division of Critical Care Medicine, Department of Pediatrics and Communicable Diseases, University of Michigan Medical School, Ann Arbor, MI 48109.
authors.forename: Tiffany T
authors.identifier: 0000-0003-2057-3204
authors.initials: TT
authors.lastname: Pham
authors.affiliation: Division of Critical Care Medicine, Department of Pediatrics and Communicable Diseases, University of Michigan Medical School, Ann Arbor, MI 48109.
authors.forename: Timothy T
authors.identifier: 0000-0001-5806-7062
authors.initials: TT
authors.lastname: Cornell
authors.affiliation: Division of Critical Care Medicine, Department of Pediatrics and Communicable Diseases, University of Michigan Medical School, Ann Arbor, MI 48109.
authors.forename: Kelli L
authors.initials: KL
authors.lastname: McDonough
authors.affiliation: Division of Critical Care Medicine, Department of Pediatrics and Communicable Diseases, University of Michigan Medical School, Ann Arbor, MI 48109.
authors.forename: Walker M
authors.identifier: 0000-0003-3194-8833
authors.initials: WM
authors.lastname: McHugh
authors.affiliation: Division of Pediatric Nephrology, Department of Pediatrics and Communicable Diseases, C.S. Mott Children's Hospital, University of Michigan Medical School, Ann Arbor, MI 48109; and.
authors.forename: Neal B
authors.initials: NB
authors.lastname: Blatt
authors.affiliation: Division of Critical Care Medicine, Department of Pediatrics and Communicable Diseases, University of Michigan Medical School, Ann Arbor, MI 48109.
authors.forename: Mary K
authors.identifier: 0000-0001-7329-1943
authors.initials: MK
authors.lastname: Dahmer
authors.affiliation: Department of Pediatrics, Lurie Children's Hospital of Chicago, Feinberg School of Medicine, Northwestern University, Evanston, IL 60611.
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Shanley
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000276:immunology*; D000818:Animals; D015153:Blotting, Western; D004195:Disease Models, Animal; D004731:Endotoxins / Q000276:immunology; D004927:Escherichia coli Infections / Q000276:immunology; D007113:Immunity, Innate; D047468:Immunoprecipitation; D007249:Inflammation / Q000276:immunology; D008264:Macrophages / Q000276:immunology*; D051379:Mice; D018345:Mice, Knockout; D022423:Myeloid Cells / Q000276:immunology; D053594:Myeloid Differentiation Factor 88 / Q000276:immunology*; D020411:Oligonucleotide Array Sequence Analysis; D016133:Polymerase Chain Reaction; D000071636:Protein Phosphatase 2C / Q000172:deficiency / Q000378:metabolism*; D018805:Sepsis / Q000276:immunology; D015398:Signal Transduction / Q000276:immunology*; D059467:Transcriptome
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D004731:Endotoxins; D053594:Myeloid Differentiation Factor 88; D000071636:Protein Phosphatase 2C; C507780:Myd88 protein, mouse; C476286:Ticam1 protein, mouse; C000607466:Ppm1a protein, mouse