Dataset Information

Fractionation of phosphopeptides using reversed phase microcolumn prior to LC-MS analysis

ABSTRACT: A protocol for an improved phosphopeptide identification in tryptically digested complex peptide samples is described. The common TiO2 based phoshopeptide enrichment is coupled to a simple peptide fractionation protocol with following LC-MS analysis of the obtained fractions and proteomic identification of phosphorylated peptides. The fractions are obtained by an optimized protocol for peptide fractionation using a home-made capillary column coupled to a microgradient elution using a gastight microsyringe. The protocol leads to a substantially increased number of phosphopeptides (more than twice).

INSTRUMENT(S): Q Exactive

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Cell Culture

SUBMITTER: Pavel Rehulka

LAB HEAD: Jiri Stulik

PROVIDER: PXD018663 | Pride | 2020-08-31

REPOSITORIES: Pride

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Publications

Fractionation of Enriched Phosphopeptides Using pH/Acetonitrile-Gradient-Reversed-Phase Microcolumn Separation in Combination with LC-MS/MS Analysis.

Ondrej Martin M Rehulka Pavel P Rehulkova Helena H Kupcik Rudolf R Tichy Ales A

International journal of molecular sciences 20200601 11

Mass spectrometry (MS) is a powerful and sensitive method often used for the identification of phosphoproteins. However, in phosphoproteomics, there is an identified need to compensate for the low abundance, insufficient ionization, and suppression effects of non-phosphorylated peptides. These may hamper the subsequent liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) analysis, resulting in incomplete phosphoproteome characterization, even when using high-resolution instrument ...[more]

PMID: 32492839

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Project description:Coordinated migration of B cells within and between secondary lymphoid tissues is required for robust antibody responses to infection or vaccination. Secondary lymphoid tissues normally expose B cells to a low O2 (hypoxic) environment. Recently, we have shown that human B cell migration is modulated by an O2-dependent molecular switch, centrally controlled by the hypoxia-induced (transcription) factor-1a (HIF1A), which can be disrupted by the immunosuppressive calcineurin inhibitor, cyclosporine A (CyA). However, the mechanisms by which low O2 environments attenuate B cell migration remain poorly defined. Proteomics analysis has linked CXCR4 chemokine receptor signaling to cytoskeletal rearrangement. We now hypothesize that the pathways linking the O2 sensing molecular switch to chemokine receptor signaling and cytoskeletal rearrangement would likely contain phosphorylation events, which are typically missed in traditional transcriptomic and/or proteomic analyses. Hence, we have performed a comprehensive phosphoproteomics analysis of human B cells treated with CyA after engagement of the chemokine receptor CXCR4 with CXCL12. Statistical analysis of the separate and synergistic effects of CyA and CXCL12 revealed 116 proteins whose abundance is driven by a synergistic interaction between CyA and CXCL12. Among these 116 proteins, Lymphocyte Specific Protein 1 (LSP1) was most interesting due to its original identification as a protein modulating neutrophil migration. We used our previously described algorithm BONITA to reveal a critical role for LSP1 in cytoskeletal rearrangement. Validating these modeling results, we show experimentally that LSP1 levels in B cells increase with low O2 exposure, and CyA treatment results in decreased LSP1 protein levels. This correlates with the increased chemotactic activity observed after CyA treatment. Lastly, we directly link LSP1 levels to chemotactic capacity, as shRNA knock-down of LSP1 results in significantly increased B cell chemotaxis at low O2 levels. These results directly link the CyA to LSP1-dependent cytoskeletal regulation, demonstrating a previously unrecognized mechanism by which CyA modulates human B cell migration.

Project description:Phosphorylation is a regulatory mechanism by which intracellular apicomplexan parasites control the process of invading and modifying host cells. However, the sporulated oocysts’ phosphoprotein repertoires between virulent and avirulent strains of Toxoplasma gondii and the underlying mechanisms contributing to virulence is still a mystery. A quantitative analysis of the sporulated oocysts’ phosphoproteome profile of T. gondii virulent and avirulent strains belonging to different genotypes was conducted to reveal phosphoprotein expression patterns that contribute to the virulence of a particular phenotype. Phosphopeptides from the sporulated oocysts of the virulent strain PYS (Chinese ToxoDB#9) and the avirulent strain type II (PRU strain) were enriched by titanium dioxide (TiO2) affinity chromatography and quantified using iBT technology. A total of 10,645 unique phosphopeptides, 8,181 nonredundant phosphorylation sites and 2,792 phosphoproteins were identified. The quantitative analysis identified 4,129 differentially expressed phosphopeptides (DEPs) between sporulated oocysts of the PYS strain and PRU strain (|log1.5 fold change| > 1 and P < 0.05), including 2,485 upregulated and 1,644 downregulated phosphopeptides. Motif analysis identified 24 motifs from the upregulated phosphorylated peptides including 22 serine motifs and two threonine motifs (TPE and TP), and 15 motifs from the downregulated phosphorylated peptides including 12 serine motifs and three threonine motifs (TP, RxxT and KxxT) in PYS strain when comparing PYS/PRU. Several kinases were consistent with motifs of overrepresented phosphopeptides, such as PKA, PKG, CKII, IKK, MAPK, EGFR, INSR, Jak, Syk, Src, Ab1. GO analysis, KEGG pathway analysis and STRING analysis revealed differentially expressed phosphoproteins (DEPs) exhibiting significant functional properties. Kinase associated network analysis showed that AGC kinase had the greatest connected peptides. Our findings reveal significant difference in phosphopeptides of sporulated oocysts between virulent and avirulent T. gondii strains, which provides solid foundation for further exploring the mechanisms contributing to the virulence of T. gondii.

Dataset Information

Fractionation of phosphopeptides using reversed phase microcolumn prior to LC-MS analysis

Publications

Fractionation of Enriched Phosphopeptides Using pH/Acetonitrile-Gradient-Reversed-Phase Microcolumn Separation in Combination with LC-MS/MS Analysis.

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