title: The proteomic profile of circulating pentraxin 3 (PTX3) complex in sepsis demonstrates the interaction with azurocidin 1 and other components of neutrophil extracellular traps.
abstract: Pentraxin 3 (PTX3), a long pentraxin subfamily member in the pentraxin family, plays an important role in innate immunity as a soluble pattern recognition receptor. Plasma PTX3 is elevated in sepsis (~200 ng/ml) and correlates with mortality. The roles of PTX3 in sepsis, however, are not well understood. To investigate the ligands of PTX3 in sepsis, we performed a targeted proteomic study of circulating PTX3 complexes using magnetic bead-based immunopurification and shotgun proteomics for label-free relative quantitation via spectral counting. From septic patient fluids, we successfully identified 104 candidate proteins, including the known PTX3-interacting proteins involved in complement activation, pathogen opsonization, inflammation regulation, and extracellular matrix deposition. Notably, the proteomic profile additionally showed that PTX3 formed a complex with some of the components of neutrophil extracellular traps. Subsequent biochemical analyses revealed a direct interaction of bactericidal proteins azurocidin 1 (AZU1) and myeloperoxidase with PTX3. AZU1 exhibited high affinity binding (K(D) = 22 ± 7.6 nm) to full-length PTX3 in a calcium ion-dependent manner and bound specifically to an oligomer of the PTX3 N-terminal domain. Immunohistochemistry with a specific monoclonal antibody generated against AZU1 revealed a partial co-localization of AZU1 with PTX3 in neutrophil extracellular traps. The association of circulating PTX3 with components of the neutrophil extracellular traps in sepsis suggests a role for PTX3 in host defense and as a potential diagnostic target.
authors.affiliation: Department of Molecular Biology and Medicine, Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo 153-8904, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Daigo
authors.forename: Naotaka
authors.initials: N
authors.lastname: Yamaguchi
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kawamura
authors.forename: Koichi
authors.initials: K
authors.lastname: Matsubara
authors.forename: Shuying
authors.initials: S
authors.lastname: Jiang
authors.forename: Riuko
authors.initials: R
authors.lastname: Ohashi
authors.forename: Yukio
authors.initials: Y
authors.lastname: Sudou
authors.forename: Tatsuhiko
authors.initials: T
authors.lastname: Kodama
authors.forename: Makoto
authors.initials: M
authors.lastname: Naito
authors.forename: Kenji
authors.initials: K
authors.lastname: Inoue
authors.forename: Takao
authors.initials: T
authors.lastname: Hamakubo
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000097:blood* / Q000737:chemistry; D015415:Biomarkers / Q000097:blood; D001798:Blood Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D002097:C-Reactive Protein / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D019556:COS Cells; D002118:Calcium / Q000737:chemistry; D002352:Carrier Proteins / Q000097:blood* / Q000737:chemistry; D002522:Chlorocebus aethiops; D005260:Female; D006801:Humans; D047468:Immunoprecipitation; D046911:Macromolecular Substances / Q000097:blood; D008297:Male; D008875:Middle Aged; D009504:Neutrophils / Q000378:metabolism*; D009195:Peroxidase / Q000097:blood / Q000302:isolation & purification; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D040901:Proteomics; D022142:Secretory Vesicles / Q000378:metabolism; D018805:Sepsis / Q000097:blood*; D000683:Serum Amyloid P-Component / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D000099153:Pentraxins
chemical_list: D023181:Antimicrobial Cationic Peptides; D015415:Biomarkers; D001798:Blood Proteins; D002097:C-Reactive Protein; D002118:Calcium; D002352:Carrier Proteins; D046911:Macromolecular Substances; D009195:Peroxidase; D000683:Serum Amyloid P-Component; D000099153:Pentraxins; C062991:AZU1 protein, human