Dataset Information

Early Signaling Dynamics of EGFR

ABSTRACT: Despite extensive study of the epidermal growth factor receptor (EGFR) signaling network, the immediate post-translational changes that occur in response to growth factor stimulation remain poorly characterized; as a result, the biological mechanisms underlying signaling initiation remain obscured. To address this deficiency, we have used a mass spectrometry-based approach to measure system-wide phosphorylation changes throughout the network with 10 second resolution in the 80 seconds after stimulation in response to a range of 8 growth factor concentrations. Significant changes were observed on proteins far downstream in the network as early as 10 seconds after stimulation, indicating a system capable of transmitting information quickly. Meanwhile, canonical members of the EGFR signaling network fall into clusters with distinct activation patterns. Shc and PI3K phosphorylation levels increase rapidly, but equilibrate within 20 s, while proteins like Gab1 and SHP2 show slower, sustained increases. Proximity ligation assays reveal that Shc and Gab1 phosphorylation patterns are representative of separate timescales for physical association with the receptor. Inhibition of phosphatases with vanadate reveals site-specific regulatory mechanisms, and also uncovers primed activating components in the network, including Src family kinases, whose inhibition impacts only a subset of proteins within the network. The results presented highlight the complexity of signaling initiation, and provide a window into exploring mechanistic hypotheses about RTK biology.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Epithelial Cell, Cell Culture

SUBMITTER: Raven Reddy

LAB HEAD: Forest White

PROVIDER: PXD003660 | Pride | 2016-06-24

REPOSITORIES: Pride

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Publications

Early signaling dynamics of the epidermal growth factor receptor.

Reddy Raven J RJ Gajadhar Aaron S AS Swenson Eric J EJ Rothenberg Daniel A DA Curran Timothy G TG White Forest M FM

Proceedings of the National Academy of Sciences of the United States of America 20160229 11

Despite extensive study of the EGF receptor (EGFR) signaling network, the immediate posttranslational changes that occur in response to growth factor stimulation remain poorly characterized; as a result, the biological mechanisms underlying signaling initiation remain obscured. To address this deficiency, we have used a mass spectrometry-based approach to measure system-wide phosphorylation changes throughout the network with 10-s resolution in the 80 s after stimulation in response to a range o ...[more]

PMID: 26929352

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Project description:Mutations in the epidermal growth factor receptor (EGFR) kinase domain occur in 10-30% of lung adenocarcinoma. Leucine to arginine substitution at amino acid position 858 (L858R) accounts for around 50% of EGFR-tyrosine kinase inhibitor (TKI) sensitizing mutations. A second site mutation in the gatekeeper residue (T790M) accounts for around 60% of acquired resistance to EGFR-TKIs. We sought to identify the immediate direct and indirect targets of these mutant EGFRs in lung adenocarcinoma and their modulation by erlotinib, the first generation, and most widely used EGFR-directed TKI. We undertook stable isotope labeling of amino acids in cell culture (SILAC), phosphopeptide enrichment, and quantitative mass spectrometry to identify dynamic changes of phosphorylation downstream of mutant EGFRs in lung adenocarcinoma cells harboring L858R or L858R/T790M mutations and their modulation by erlotinib inhibition. Phosphorylation at the majority of phosphosites identified exhibited no change upon either EGF stimulation or erlotinib inhibition. Only around 7% of phosphosites identified and quantified showed increased phosphorylation upon EGF stimulation in either cell line. However, while phosphorylation at 61% of these phosphosites decreased upon erlotinib inhibition in the TKI sensitive H3255 cells, only 24% of such sites exhibited decreased phosphorylation upon erlotinib inhibition in the TKI resistant H1975 cells. Top canonical pathways that were inhibited upon erlotinib treatment in sensitive cells, but not the resistant cells include EGFR, Insulin receptor, HGF, MAPK, mTOR, p70S6K and JAK/STAT signaling. We identified phosphosites in proteins of the autophagy network, such as ULK1 (S623) that is constitutive phosphorylated in these lung adenocarcinoma cells, but phosphorylation is inhibited upon erlotinib treatment in sensitive cells, but not resistant cells. Finally, kinase-substrate prediction analysis from our data indicated that substrates of basophilic kinase families, AGC, CAMK and STE were significantly enriched and those of proline directed kinase families, CMGC and CK were significantly depleted among substrates that exhibit increased phosphorylation upon EGF stimulation and reduced phosphorylation upon TKI inhibition. This is the first study to date to examine global phosphorylation changes upon erlotinib treatment of lung adenocarcinoma cells and results from this study provide new insights into signaling downstream of mutant EGFRs in lung adenocarcinoma.

Project description:Cysteine is a rare and conserved amino acid involved in most cellular functions. The thiol group of cysteine can be subjected to diverse oxidative modifications that regulate most physio-pathological states. Here, a Cysteine-specific Phosphonate Adaptable Tag (CysPAT) was synthesized to selectively label cysteine-containing peptides (Cys peptides) followed by enrichment with titanium dioxide (TiO2) and mass spectrometric analysis. The CysPAT strategy was developed using a synthetic peptide, a standard protein and subsequently the strategy was applied to Hela cells lysate, achieving high specificity and enrichment efficiency. In particular,From 500µg of Hela cell lysate, the method led to the identification of 9229 unique Cys peptides starting from 500µg of Hela cell lysate . the CysPAT labelled Cys peptides showed increased hydrophobicity. Finally, the method was further developed to simultaneously enrich Cys peptides and phosphorylated peptidesThe method was further developed to simultaneously enrich Cys peptides and phosphorylated peptides from SILAC labelled Hela cells subjected to 5 min epidermal growth factor (EGF) stimulation. In total, of 22972 unique reversibly modified Cys peptides (3886 proteins) and 18549 unique phosphopeptides (2257 proteins) were simultaneously identified by Orbitrap Fusion. Significant regulation was observed in both phosphorylation and reversible Cys modification of proteins interacted with EGF receptor (EGFR)-binding proteins and proteins involved in EGFR signaling pathway. EGF stimulation can activate the phosphorylation of EGFR and downstream signaling molecules, such as mitogen-activated protein kinases (MAPK1 and MAPK3), meanwhile, it also leads to the activation of multiple protein tyrosine phosphatases (PTPs) by reduction of the catalytic Cys site in the conserved putative phosphatase HC(X)5R motif, Llater the activated PTPs would dephosphorylate and inactivate the molecules activated by EGF stimulation. Overall, the CysPAT strategy is a promising tool for studying redox proteomics and the simultaneous enrichment strategy offers an excellent solution for characterization of cross-talk between phosphorylation and redox induced cysteine modifications.

Project description:Aberrant activation of Hedgehog (HH) signaling has been identified as a key etiologic factor of many human malignancies. Signal strength, target gene specificity, and oncogenic activity of HH signaling profoundly depend on interactions with other pathways such as epidermal growth factor receptor-mediated signaling which has been shown to cooperate with HH/GLI in basal cell carcinoma and pancreatic cancer. We demonstrate that the human medulloblastoma cell line Daoy possesses a fully inducible endogenous HH pathway. Treatment of Daoy cells with Sonic Hedgehog or Smoothened agonist induced expression of GLI1 protein and prevented processing of GLI3 to its repressor form. To study interactions between HH- and EGF-induced signaling in greater detail, time-resolved measurements were carried out and analyzed on the transcriptomic as well as proteomic level. Daoy cells responded to the co-treatment by downregulating GLI1, PTCH, and HHIP on the transcript level which was also seen when Amphiregulin (AREG) was used instead of EGF. The finding that EGFR signaling silences proteins acting as negative regulators of HH signaling is firstly described here as a novel crosstalk mechanism. Furthermore, combined EGFR/HH signaling maintains high GLI1 protein levels contrasting its downregulation on the transcript level. On the other hand, high level synergism was observed with respect to a strong and significant upregulation of numerous canonical EGF-targets with putative tumor-promoting properties such as MMP7, VEGFA, and IL-8. In conclusion, synergistic effects between EGFR and HH signaling can selectively induce a switch from a canonical HH/GLI profile to a modulated specific target gene profile pointing to more wide-spread, yet context-dependent, interactions between HH/GLI and growth factor receptor signaling in human malignancies. To study interactions between HH- and EGF-induced signaling, time-resolved measurements were carried out over a period of 24 h at 14 different time points after stimulation by EGF with and without additional stimulation by SHH. Furthermore, as a control, cells without any stimulation by EGF and SHH (control) and cells in the presents of SHH were analyzed. Overall, three biological replicates of 60 different treatment/timepoints were analyzed yielding 180 different samples.

Dataset Information

Early Signaling Dynamics of EGFR

Publications

Early signaling dynamics of the epidermal growth factor receptor.

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