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Ultra-deep tyrosine phosphoproteome analysis enabled by an SH2 domain-derived phosphotyrosine superbinder

ABSTRACT: We present a new strategy for systematic identification of phosphotyrosine (pTyr) by AP-MS using an SH2 domain-derived pTyr-superbinder as the affinity reagent. The superbinder allows for markedly deeper and broader coverage of the Tyr phosphoproteome than conventional anti-phosphotyrosine antibodies when an optimal amount is used. Indeed, we identified approximately 20,000 distinct phosphotyrosyl peptides and more than 10,000 pTyr sites, of which 36% are novel, from 9 cell lines using the superbinder approach. Intriguingly, tyrosine kinases, SH2 domains and phosphotyrosine phosphatases were found preferably phosphorylated, suggesting that the toolkit of kinase signaling is subjected to intensive regulation by phosphorylation. Cell type-specific global kinase activation patterns inferred from label-free quantitation of Tyr phosphorylation guided the design of experiments to inhibit cancer cell proliferation by blocking the highly activated tyrosine kinases. Therefore, the superbinder is a highly efficient and cost-effective alternative to conventional antibodies for systematic and quantitative analysis of the tyrosine phosphoproteome under normal or pathological conditions.

INSTRUMENT(S): LTQ Orbitrap Velos

ORGANISM(S): Homo Sapiens (ncbitaxon:9606)

SUBMITTER: hanfa Zou; Shawn Li

PROVIDER: MSV000079489 | MassIVE | Wed Feb 03 02:09:00 GMT 2016

SECONDARY ACCESSION(S): PXD003563

REPOSITORIES: MassIVE

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Project description:Albeit much less abundant than Ser/Thr phosphorylation (pSer/pThr), Tyr phosphorylation (pTyr) is considered a hallmark in cellular signal transduction. However, its analysis remains a challenge. The conventional immunopurification (IP) approach using antibodies pan-specific to pTyr sites is known to have low sensitivity, poor reproducibility and high cost. SH2 domain-derived pTyr-superbinder is a good replacement of pTyr antibody for the specific enrichment of pTyr peptides for phosphoproteomics analysis. In this study, we aim to optimize the approach using SH2 superbinder for tyrosine phosphoproteome analysis. The present work covalently immobilized SH2 superbinders to agrose beads, designed and evaluated four different SH2 superbinder based experimental workflows for phosphotyrosine analysis. After made a head to head comparison of them, we observed that the combined strategy employing Ti4+-IMAC and covalently immobilized SH2 superbinder enrichment in sequence generated the largest pTyr peptide dataset (3519) with the best selectivity (90%). Next the optimal method was applied for pTyr profiling from normal mouse tissues, and resulted in the identification of 197 pTyr sites (of which 73 were novel) from 5 mg protein digests, which validated its high sensitivity. An comparison with antibody 4G10 by isolating pTyr peptides from 5 mg unstimulated Jurkat cell digests were made, our optimal strategy identified 343 while the antibody 4G10 based method identified 242 pTyr sites, respectively, further confirmed the robustness of the method. Finally, the optimal strategy was applied for quantitative pTyr phosphorylation analysis of EGF stimulated/unstimulated HeLa cells, 261 pTyr sites were successfully quantified from 5 mg stable-isotope dimethyl labling protein digests. In general, the combination of Ti4+-IMAC and SH2 superbinder enrichment in sequence generated a facial and robust strategy for qualitative and quantitative analysis of pTyr proteome.

Project description:Dynamic tyrosine phosphorylation is fundamental to a myriad of cellular processes. However, the inherently low abundance of tyrosine phosphorylation in the proteome and the inefficient enrichment of phosphotyrosine(pTyr)-containing peptides has led to poor pTyr peptide identification and quantitation, critically hindering researchers’ ability to elucidate signaling pathways regulated by tyrosine phosphorylation in systems where cellular material is limited. The most popular approaches to wide-scale characterization of the tyrosine phosphoproteome use pTyr enrichment with pan-specific, anti-pTyr antibodies from a large amount of starting material. Methods that decrease the amount of starting material and increase the characterization depth of the tyrosine phosphoproteome while maintaining quantitative accuracy and precision would enable the discovery of tyrosine phosphorylation networks in rarer cell populations. To achieve these goals, a novel method leveraging the multiplexing capability of tandem mass tags (TMT) and the use of trigger channels – cells treated with the promiscuous tyrosine phosphatase inhibitor pervanadate (PV) – selectively increased the relative abundance of pTyr-containing peptides. After PV facilitated selective fragmentation of pTyr-containing peptides, TMT reporter ions delivered sensitive quantitation of each peptide for the experimental samples while the quantitation from PV trigger channels was ignored. This method yielded up to 6.3-fold boost in quantification depth of statistically significant data derived from contrived ratios, compared to TMT without trigger channels or intensity-based label-free (LF) quantitation while maintaining quantitative accuracy and precision, allowing quantitation of over 2300 unique pTyr peptides from only 1 mg of T cell receptor-stimulated Jurkat T cells. The trigger channel strategy can potentially be applied in analyses of other post-translational modifications where treatments that broadly boost the levels of those modifications across the proteome are available.

Project description:Tumor-associated macrophages (TAMs), often adopting an immunosuppressive M2-like phenotype, correlate with unfavorable cancer outcomes. Our investigation unveiled elevated expression of the butyrophilin (BTN)2A1 in M2-like TAMs across diverse cancer types. We developed anti-BTN2A1 monoclonal antibodies (mAb) and notably, one clone demonstrated a robust inhibitory effect on M2-like macrophage differentiation, inducing a shift towards an M1-like phenotype both in vitro and ex vivo in TAMs from patients with cancer. Macrophages treated with this anti-BTN2A1 mAb exhibited enhanced support for T-cell proliferation and IFNγ secretion. Indeed, M1-like and M2-like macrophage differentiation involves complex signaling pathways leading to specific gene expression profiles. Typically, stimuli from the TME induce pathways including JAK/STATs, MAPK, PI3K/AKT, NOTCH and NF-κB influencing TAMs polarization. We investigated the signaling pathways activated in monocytes and M-CSF-induced M2-like macrophages upon BTN2A1 engagement using anti-BTN2A mAb5. After 30 min of treatment, we observed phosphorylation of MAPKs (i.e. ERK1/2, P38 and JNK) in CD14+ monocytes and in M2-like macrophages, unlike isotype control-treated cells. In contrast, the PI3K/AKT, JAK/STAT, and NF-kB pathways were not consistently activated after 30 min of anti-BTN2A mAb5 treatment. Since BTN2A1 lacks intrinsic kinase activity, we explored whether BTN2A1 could form complexes with molecular partners in M2-like macrophages that provide kinase activity. We prepared lysates from M2-like macrophages treated with mAb5 or with its isotype control for 30 min and performed immunoprecipitation (IP) using another anti-BTN2A mAb followed by western blotting with anti-phosphoTyrosine (pTyr). A 70 kDa was co-immunoprecipitated with BTN2A1 and revealed by the anti-pTyr in lysates from anti-BTN2A mAb5-treated M2-like macrophages. To identify which Tyrosine kinase is enriched in anti-BTN2A mAb5-treated M2-like macrophages, we performed LC-MS/MS on anti-pTyr immunoprecipitates from treated cells. Several tyrosine kinases, including P38α/δ and JNK, were enriched. Notably, SYK was also identified and matched the 72kDa molecular weight of the pTyr band co-immunoprecipitated with BTN2A1.

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Ultra-deep tyrosine phosphoproteome analysis enabled by an SH2 domain-derived phosphotyrosine superbinder

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