Project description:Previously, we published a dataset of human blood plasma and serum samples of 10 healthy males and 10 healthy females, fractionated on a set of sorbents (cation exchange Toyopearl CM-650M, CM Bio-Gel A, SP Sephadex C-25 and anion exchange QAE Sephadex A-25) and analyzed by LC-MS/MS individually and pooled in equal amounts (Supplementary Table S1, Sheet 1) [33]. Blood is a complex tissue and can theoretically contain products of all processes occurring in different parts of the body. To identify potential sources of “alien” (non-human) plasma peptides, we performed a de novo analysis of mass spectrometry data. De novo analysis is a less efficient method of identification than search against databases, since the accuracy and resolution of modern mass spectrometers such as QTOF or Orbitrap remains not high enough. However, we use de novo analysis to identify organisms that include the most abundant components of the complex peptide mixture. This procedure allows us to develop a hypothesis and then perform a standard search against a database of proteins of identified organisms. The de novo identification was carried out using PEAKS Studio 8.0 (Bioinformatics Solutions Inc., Canada) and mass spectrometry driven BLAST analysis against the RefSeq non-redundant database NCBInr (https://www.ncbi.nlm.nih.gov/protein/). Mass spectra identified as fragments of proteins from different organisms were assigned to a taxonomic level at which these different organisms converged (Supplementary Table S2). 33. Arapidi, G. et al. Peptidomics dataset: Blood plasma and serum samples of healthy donors fractionated on a set of chromatography sorbents. Data Brief 18, 1204–1211 (2018).
Project description:Introduction: Autoreactivity to histones is a pervasive feature of several human autoimmune disorders including systemic lupus erythematosus (SLE). Specific post-translational modifications (PTMs) of histones within neutrophil extracellular traps (NETs) may potentially drive the process by which tolerance to these chromatin-associated proteins is broken. We hypothesized that NETs and their unique histone PTMs might be capable of inducing autoantibodies that target histones. Methods: We developed a novel and efficient method for the in vitro production, visualization, and broad profiling of histone-PTMs of human and murine NETs. We also immunized Balb/c mice with murine NETs and profiled their sera on autoantigen and histone peptide microarrays for evidence of autoantibody production to their immunogen. Results: We confirmed specificity toward acetyl-modified histone H2B as well as to other histone PTMs in sera from patients with SLE known to have autoreactivity against histones. We observed enrichment for distinctive histone marks of transcriptionally silent DNA during NETosis triggered by diverse stimuli. However, NETs derived from human and murine sources did not harbor many of the PTMs toward which autoreactivity was observed in patients with SLE or in MRL/lpr mice. Further, while murine NETs were weak autoantigens in vivo, there was only partial overlap in the IgG and IgM autoantibody profiles induced by vaccination of mice with NETs and those seen in patients with SLE. Conclusions: Isolated in vivo exposure to NETs is insufficient to break tolerance and may involve additional factors that have yet to be identified. Serum samples from 20 systemic lupus erythematosis patients were run on the Human Epigenome Microarray Platform V1.0 (HEMP; a single-color platform), in order to profile their autoantibodies against a library of post-translationally modified histone peptides. These 20 samples were randomly selected from a larger cohort previously profiled (data not shown) on the Utz Lab Whole Protein Autoantigen Array V2.0 (a single-color platform), where 14 were histone-reactive and 6 were histone-nonreactive. Control sera from 9 healthy adults and a positive control comprising a mixture of autoimmune sera with defined reactivities, were also run on HEMP V1.0. Together, these samples comprise the data appearing in Figures 1 and S1 (IgG and IgM isotype reactivity profiles, respectively), identifying IgG reactivity to 9 peptides that significantly distinguish histone-reactive from -nonreactive sera among 96 peptides profiled. For data appearing in Figure 5, serum samples from a total of 6 Balb/c mice, consisting of two treatment groups, NETs (Neutrophil Extracellular Traps) and NETs + CRAMP (cathelicidin-related antimicrobial peptide) were collected monthly over a 3-month period, along with a zero time point. These samples were compared with a positive control consisting of serum collected from a MLR/lpr mice exhibiting lupus-like symptoms, and a negative control with no serum. The 0, 1 and 2 month time points were profiled on the Utz Lab Whole Protein Autoantigen Array V2.0 and are shown in Figure 5A-B, while the 1 and 3 month time points were profiled on HEMP V1.0 arrays and shown in Figure 5E. All samples were run once with no replicates.
Project description:We performed nanoLC-MS/MS analysis of an in vitro generated, trypsin-digested brominated human serum albumin standard, spiked into a complex trypsin-digested proteomic background, in an LTQ-Orbitrap instrument. We found that brominated peptides spiked in at a 1-10% ratio (mass:mass) were easily identified by manual inspection when higher-energy collisional dissociation (HCD) and collision induced dissociation (CID) were employed as the dissociation mode; however, confident assignment of brominated peptides from protein database searches required a novel approach. By addition of a custom modification, corresponding to the substitution of a single bromine with 81Br rather than 79Br for dibromotyrosine (79Br81BrY), the number of validated assignments for peptides containing dibromotyrosine increased significantly when analyzing both high resolution and low resolution MS/MS data.
Project description:Albuminome from human serum was isolated using ProteaPrep HSA affinity spin columns and Vivapure anti-HSA spin columns. Albuminome from CSF was isolated using ProteaPrep HSA affinity spin columns. Isolated albuminome was trypsin digested and analyzed by LC-MS/MS to determine serum and CSF albuminome proteins. All raw MS/MS data originating from the Orbitrap Elite were batch searched based on albuminome isolation method (ProteaPrep vs. Vivapure). A total of 9 files were acquired for each albuminome analyzed (3 technical reps x 3 MS technical reps). All data were searched using the Sorcerer 2TM-SEQUEST algorithm (Sage-N Research, Milpitas, CA, USA) using default peak extraction parameters. Data were searched against the Human Uniprot database (July 2012) with an Xcorr cutoff of 1.7 using the following criteria: Fixed modification: +57 on C (carbamidomethyl); Variable modification: +16 on M (oxidation); Enzyme: Trypsin with 2 max missed cleavages; Parent Tolerance: 50 ppm; Fragment tolerance: 1.00 Da. Post-search analysis was performed using Scaffold 3 version 3.6.2 (Proteome Software, Inc., Portland, OR, USA) with protein and peptide probability thresholds set to 95% and 90%, respectively, and one peptide required for identification. Protein and peptide false discovery rates were calculated automatically using Scaffold’s probabilistic method and were equal to or less than 0.5 % for all samples using the above thresholds. Data were imported in Protein Center (Proxeon/ThermoFisher) and all data were clustered by indistinguishable proteins to remove protein redundancy within data sets. Only proteins that were observed in all three technical replicates were included in the final protein list, although proteins observed it at least two technical replicates were included in the on-line supplement for reference.
Project description:We have develop a proteogenomics-based approach for identification of human MHC class I-associated peptides, including those deriving from polymorphisms, mutations and non-canonical reading frames
Project description:Seeking to identify HLA class I peptides that originate from vaccinia virus proteins to understand the mechanism of immune protection. Note that vaccinia-infected B cells will still continue to present (primarily) a wide variety of peptides originating from endogenous proteins; this data set contains evidence for more than 5000 such peptides. The objective and challenge is to detect and identify the peptides that originate from the pathogen (vaccinia virus) in the presence (background) of this large number of endogensous 'self' peptides. Keywords: Peptide search results from multiple injections of multiple strong cation exchange fractions combined into one set of results.
Project description:Biologically uncommon d-aspartate (d-Asp) residues have been shown to accumulate in proteins associated with age-related human disorders, such as cataract and Alzheimer disease. Such d-Asp-containing proteins are unlikely to be broken down completely because metabolic enzymes recognize only proteins or peptides composed exclusively of l-amino acids. Therefore, undigested d-Asp-containing peptides may exist in blood and, if detectable, may be a useful biomarker for associated diseases. In this study, we investigated d-amino acid-containing peptides in adult human serum by a qualitative d-amino acid analysis based on a diastereomer method and LC-MS/MS method. As a result, two d-Asp-containing peptides were detected in serum, both derived from the fibrinogen ?-chain, a glycoprotein that helps in the formation of blood clots. One of the peptides was fibrinopeptide B, which prevents fibrinogen from forming polymers of fibrin, and the other was same peptide with C-terminal Arginine missing. To our knowledge, this is the first report of the presence of d-amino acid-containing peptides in serum and the approach described will provide a new direction on the serum proteome and fragmentome.
Project description:Introduction: Autoreactivity to histones is a pervasive feature of several human autoimmune disorders including systemic lupus erythematosus (SLE). Specific post-translational modifications (PTMs) of histones within neutrophil extracellular traps (NETs) may potentially drive the process by which tolerance to these chromatin-associated proteins is broken. We hypothesized that NETs and their unique histone PTMs might be capable of inducing autoantibodies that target histones. Methods: We developed a novel and efficient method for the in vitro production, visualization, and broad profiling of histone-PTMs of human and murine NETs. We also immunized Balb/c mice with murine NETs and profiled their sera on autoantigen and histone peptide microarrays for evidence of autoantibody production to their immunogen. Results: We confirmed specificity toward acetyl-modified histone H2B as well as to other histone PTMs in sera from patients with SLE known to have autoreactivity against histones. We observed enrichment for distinctive histone marks of transcriptionally silent DNA during NETosis triggered by diverse stimuli. However, NETs derived from human and murine sources did not harbor many of the PTMs toward which autoreactivity was observed in patients with SLE or in MRL/lpr mice. Further, while murine NETs were weak autoantigens in vivo, there was only partial overlap in the IgG and IgM autoantibody profiles induced by vaccination of mice with NETs and those seen in patients with SLE. Conclusions: Isolated in vivo exposure to NETs is insufficient to break tolerance and may involve additional factors that have yet to be identified. Serum samples from 20 systemic lupus erythematosis patients were run on the Human Epigenome Microarray Platform V1.0 (HEMP; a single-color platform), in order to profile their autoantibodies against a library of post-translationally modified histone peptides. These 20 samples were randomly selected from a larger cohort previously profiled (data not shown) on the Utz Lab Whole Protein Autoantigen Array V2.0 (a single-color platform), where 14 were histone-reactive and 6 were histone-nonreactive. Control sera from 9 healthy adults and a positive control comprising a mixture of autoimmune sera with defined reactivities, were also run on HEMP V1.0. Together, these samples comprise the data appearing in Figures 1 and S1 (IgG and IgM isotype reactivity profiles, respectively), identifying IgG reactivity to 9 peptides that significantly distinguish histone-reactive from -nonreactive sera among 96 peptides profiled. For data appearing in Figure 5, serum samples from a total of 6 Balb/c mice, consisting of two treatment groups, NETs (Neutrophil Extracellular Traps) and NETs + CRAMP (cathelicidin-related antimicrobial peptide) were collected monthly over a 3-month period, along with a zero time point. These samples were compared with a positive control consisting of serum collected from a MLR/lpr mice exhibiting lupus-like symptoms, and a negative control with no serum. The 0, 1 and 2 month time points were profiled on the Utz Lab Whole Protein Autoantigen Array V2.0 and are shown in Figure 5A-B, while the 1 and 3 month time points were profiled on HEMP V1.0 arrays and shown in Figure 5E. All samples were run once with no replicates.