Dataset Information

Complement C5a impairs phagosomal maturation in the neutrophil through phosphoproteomic remodelling.

ABSTRACT: Critical illness is characterised by organ failure, dysregulated immune activation and frequent secondary infections. Unbridled complement activation in these patients exposes immune cells to high levels of the anaphylotoxin, C5a. C5a suppresses antimicrobial functions of key immune cells, in particular the neutrophil, and this suppression is associated with poorer outcomes amongst critically ill adults. The intracellular signalling pathways which mediate C5a-induced neutrophil dysfunction are incompletely understood. Healthy donor peripheral blood neutrophils exposed to purified C5a demonstrated a prolonged defect in phagocytosis of the common nosocomial pathogen Staphylococcus aureus which persisted for 7 hours after exposure. Phosphoproteomic profiling of 2712 unique phosphoproteins identified persistent C5a signalling at 1 hour, and selective impairment of phagosomal protein phosphorylation on exposure to S. aureus. Notable proteins included early endosomal marker ZFYVE16 and V-ATPase proton channel component ATPV1G1. A multi-function assay of bacterial ingestion and phagosomal acidification demonstrated C5a-induced impairment of phagosomal acidification in a whole blood model of Staphylococcal bacteraemia which was recapitulated in neutrophils from critically ill patients. Examination of the C5a-impaired protein phosphorylation indicated a role for the phosphatidylinositol 3-kinase VPS34 in phagosomal maturation. Inhibition of VPS34 impaired neutrophil phagosomal acidification, late bacterial ingestion and killing of S. aureus in whole blood. This study provides a deep phosphoproteomic assessment of human neutrophil signalling in response to S. aureus, and demonstrates how some of these pathways are disrupted by exposure to C5a, identifying a defect in phagosomal maturation and providing new information on mechanisms of immune failure in critical illness.

INSTRUMENT(S): Orbitrap Fusion Lumos, Q Exactive HF

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Primary Cell, Neutrophil

SUBMITTER: Carmen Gonzalez Tejedo

LAB HEAD: Andrew Conway Morris

PROVIDER: PXD017092 | Pride | 2020-08-06

REPOSITORIES: Pride

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Publications

C5a impairs phagosomal maturation in the neutrophil through phosphoproteomic remodeling.

Wood Alexander Jt AJ Vassallo Arlette M AM Ruchaud-Sparagano Marie-Hélène MH Scott Jonathan J Zinnato Carmelo C Gonzalez-Tejedo Carmen C Kishore Kamal K D'Santos Clive S CS Simpson A John AJ Menon David K DK Summers Charlotte C Chilvers Edwin R ER Okkenhaug Klaus K Morris Andrew Conway AC

JCI insight 20200806 15

Critical illness is accompanied by the release of large amounts of the anaphylotoxin, C5a. C5a suppresses antimicrobial functions of neutrophils which is associated with adverse outcomes. The signaling pathways that mediate C5a-induced neutrophil dysfunction are incompletely understood. Healthy donor neutrophils exposed to purified C5a demonstrated a prolonged defect (7 hours) in phagocytosis of Staphylococcus aureus. Phosphoproteomic profiling of 2712 phosphoproteins identified persistent C5a s ...[more]

PMID: 32634128

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Project description:Epigenetic priming factors establish a permissive epigenetic landscape which is not required until a later developmental or physiological time point, temporally uncoupling the presence of these factors with their phenotypic effects. One classic example of epigenetic priming is in the context of bivalent chromatin, found in pluripotent stem cells and early embryos at key developmental gene promoters marked by both activating-associated H3K4me3 and repressive-associated H3K27me3 histone modifications. It is currently unknown how these bivalent domains are targeted, or precisely how they impact on lineage commitment. Here we show that the small heterodimerising non-enzymatic DNA binding proteins Developmental Pluripotency Associated 2 (Dppa2) and 4 (Dppa4) act as epigenetic priming factors to establish bivalency at a subset of developmental genes. Dppa2/4 localise to the +1 nucleosome position of bivalent genes and while they are not required for pluripotency in embryonic stem cells (ESCs), double knockout cells fail to exit pluripotency and to differentiate efficiently, with delays in upregulating bivalently marked lineage genes. Proteomics reveal that Dppa2/4 interact on chromatin with members of the COMPASS and Polycomb complexes important for H3K4me3 and H3K27me3 deposition, respectively. Epigenetic profiling reveals a striking loss of H3K4me3, H3K27me3, and their associated enzymatic machinery at a significant subset of bivalent promoters in Dppa2/4 mutants, in addition to loss of H2A.Z and chromatin accessibility. In wild-type ESCs, these “Dppa2/4-dependent” bivalent promoters are characterised by low H3K4me3 enrichment and breadth, near-absent expression levels and initiating but not elongating RNA polymerase. Notably, Dppa2/4-dependent promoters are less evolutionarily conserved suggesting that they lack additional safeguard measures to maintain bivalency at these genes in the absence of Dppa2/4. Concomitantly with the loss of bivalency, Dppa2/4-dependent bivalent promoters gain DNA methylation and consequently are no longer able to be effectively activated upon ESC differentiation, leading to defects in cell fate acquisition. Our findings reveal a targeting principle for bivalency to developmental gene promoters poising them for future lineage specific gene activation.

Dataset Information

Complement C5a impairs phagosomal maturation in the neutrophil through phosphoproteomic remodelling.

Publications

C5a impairs phagosomal maturation in the neutrophil through phosphoproteomic remodeling.

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