Project description:Epidermal growth factor receptor (EGFR) signaling is frequently dysregulated in a variety of cancers. The ubiquitin ligase Cbl regulates degradation of activated EGFR through ubiquitination and acts as an adaptor to recruit proteins required for trafficking. We used Stable Isotope Labeling with Amino Acids in Cell Culture (SILAC) mass spectrometry (MS) to compare Cbl complexes in the absence and presence of EGF stimulation. We identified over a hundred novel Cbl interactors, and a secondary siRNA screen found that knockdown of Flotillin-2 (FLOT2) led to increased phosphorylation and degradation of EGFR upon EGF stimulation in HeLa cells. In H441 cells, FLOT2 knockdown increased EGF-stimulated EGFR phosphorylation, ubiquitination, and downstream signaling, reversible by the EGFR inhibitor erlotinib. CRISPR knockout of FLOT2 in HeLa cells confirmed EGFR downregulation, increased signaling, and increased dimerization and trafficking to the early endosome. FLOT2 interacts with both Cbl and EGFR. Downregulation of EGFR upon FLOT2 loss is Cbl-dependent, as co-knockdown of Cbl and Cbl-b restored EGFR levels. Stable overexpression of FLOT2 in HeLa cells decreased EGF-stimulated EGFR phosphorylation and ubiquitination. Overexpression of wild type (WT) FLOT2, but not the soluble G2A FLOT2 mutant, inhibited EGFR phosphorylation upon EGF stimulation in HEK293T cells. FLOT2 loss induces EGFR-dependent proliferation and anchorage-independent cell growth. Lastly, FLOT2 knockout increases tumor formation and tumor volume in nude mice and NSG mice, respectively. These data demonstrate that FLOT2 negatively regulates EGFR activation and dimerization, as well as its subsequent ubiquitination, endosomal trafficking, and degradation. FLOT2 negatively regulates proliferation in vitro and in vivo.
Project description:Lung cancer is the leading cause of cancer death. Mutations in the kinase domain of EGFR, a predominant driver oncogene, such as L858R missense mutation and a series of deletions spanning the conserved sequence 747LREA750, are associated with sensitivity to tyrosine kinase inhibitors (TKIs). However, patients receiving EGFR-TKIs (gefitinib and erlotinib) develop drug-resistance due to a secondary mutation at the gatekeeper residue (T790M) in about 50-60% of cases, urging for new drug development. Afatinib, a FDA approved second-generation EGFR-TKI that was developed to circumvent T790M-mediated resistance, has not been very effective in clinical trials. In this study, we performed a global phosphoproteomic screen to identify targets that undergo mutant EGFR-dependent tyrosine phosphorylation and their modulation by erlotinib or afatinib. 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 and afatinib inhibition. We identified and quantified 397, 429, 223, and 594 phosphotyrosine sites in H3255, 11-18,PC9, and H1975 cell lines that were grown in presence of FBS and in presence/absence of TKIs, respectively. These account for a total of 907 unique phospho-tyrosine sites in 496 proteins. Among them, 187 phosphotyrosine sites were found to be in 89 kinases, which may serve as intermediary regulatory kinases in EGFR signalling pathway. Further analysis indicated that in TKI-sensitive H3255 and 11-18 cells, there were 58/111 and 65/101 tyrosine sites that were hypophosphorylated in presence of erlotinib and afatinib, respectively. However, in TKI-resistant H1975 cells, 189 and 264 tyrosine sites were hypophosphorylated in presence of erlotinib and afatinib respectively, indicating that the afatinib-specific additional sites could be validated for identifying potentially new drug targets to counter TKI-resistance. Ingenuity pathway analysis (IPA) of proteins with altered phosphorylation sites demonstrated that several canonical pathways including ephrin receptor signalling and integrin signalling pathways were enriched, which may play important roles in cell growth and proliferation. However, upon EGF stimulation of serum starved H3255 cells in presence or absence of TKIs, 99 tyrosine sites that were hyperphosphorylated upon EGF stimulation were inhibited in presence of erlotinib or afatinib. But in H1975 cells treated with erlotinib, 48 of the above sites were either unchanged or were hyperphosphorylated. These sites include EGFR (Y1197/869/998), JAK1 (Y1034), FRK (Y497), GAB1 (Y657/689), MAPK1 (Y187), MAPK3 (Y204), MET (Y1252/1253). Furthermore, a total of 112 sites that were observed to be hypophosphorylated upon EGF stimulation in H1975 cells, were found to be hyperphosphorylated upon erlotinib inhibition. This could possibly be due to the activation of downstream phosphatases with EGF stimulation. We are now performing in-depth bioinformatic analysis and validation experiments using functional genomics to understand the role of targets of mutant EGFR signalling in lung cancer.
Project description:For LUM2_529995_Vehicle_24 and LUM2_529996_EGF_24, GBM12 cells were treated with vehicle or EGF for 24 hours, cells lysates were immunoprecipitated by BIN3 antibody and subjected to Mass spectrometry (MS) analysis.
For LUM2_626031_Vehicle_0pt5 and LUM2_626032_EGF_0pt5, GBM12 cells were treated with vehicle or EGF for 30 minutes, cells lysates were immunoprecipitated by EGFR antibody and subjected to Mass spectrometry (MS) analysis.
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.
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:Kholodenko1999 - EGFR signaling
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This model is described in the article:
Quantification of short term signaling by the epidermal growth factor receptor.
Kholodenko BN, Demin OV, Moehren G, Hoek JB
J. Biol. Chem. 1999 Oct; 274(42): 30169-30181
Abstract:
During the past decade, our knowledge of molecular mechanisms involved in growth factor signaling has proliferated almost explosively. However, the kinetics and control of information transfer through signaling networks remain poorly understood. This paper combines experimental kinetic analysis and computational modeling of the short term pattern of cellular responses to epidermal growth factor (EGF) in isolated hepatocytes. The experimental data show transient tyrosine phosphorylation of the EGF receptor (EGFR) and transient or sustained response patterns in multiple signaling proteins targeted by EGFR. Transient responses exhibit pronounced maxima, reached within 15-30 s of EGF stimulation and followed by a decline to relatively low (quasi-steady-state) levels. In contrast to earlier suggestions, we demonstrate that the experimentally observed transients can be accounted for without requiring receptor-mediated activation of specific tyrosine phosphatases, following EGF stimulation. The kinetic model predicts how the cellular response is controlled by the relative levels and activity states of signaling proteins and under what conditions activation patterns are transient or sustained. EGFR signaling patterns appear to be robust with respect to variations in many elemental rate constants within the range of experimentally measured values. On the other hand, we specify which changes in the kinetic scheme, rate constants, and total amounts of molecular factors involved are incompatible with the experimentally observed kinetics of signal transfer. Quantitation of signaling network responses to growth factors allows us to assess how cells process information controlling their growth and differentiation.
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Project description:Molecular switches are essential modules in signaling networks by enabling a quick response to environmental changes. Here, we describe a role for small ubiquitin-like-modifier SUMO as a molecular switch in epidermal growth factor receptor (EGFR) signaling. Using quantitative mass spectrometry, we compared the endogenous SUMO-proteomes of Hela cells before and after EGF-stimulation. Thereby, we identified a small group of transcriptional repressors, including IRF2BP1, IRF2BP2 and IRF2BPL as novel players in EGFR signaling, which lost SUMO transiently within 15 min of EGF treatment. We found 38 genes whose expression within the first hour of EGF treatment was altered in cells expressing SUMOylation deficient IRF2BP1, including Dual specific phosphatase 1 (DUSP1), an important feedback regulator of EGFR signalling. We show that IRF2BP1 binds to the proximal promoter of DUSP1, whose activation requires IRF2BP1 deSUMOylation. Thus, the SUMO-dependent molecular switch of IRF2BP1 activity is important to finely tune EGFR signaling
Project description:In the associated paper FXR1 is shown to package exceptionally long mRNAs in the cytoplasm and organizes them into an mRNP network. We performed iCLIP of FXR-WT and its mutant FXR1-V361P in HeLa cells where we knocked down endogenous FXR1 and replaced it with either GFP-tagged WT or V361P-mutant FXR1. The GFP-tagged proteins were immunoprecipitated using an anti-GFP antibody.
Project description:Lupus nephritis (LN) often results in progressive renal dysfunction. The inactive Rhomboid 2 (iRhom2) is a newly identified key regulator of A disintegrin and metalloprotease 17 (ADAM17), whose substrates, such as TNF-α and heparin-binding EGF (HB-EGF), have been implicated in the pathogenesis of chronic kidney disease. Here we demonstrate that deficiency of iRhom2 protects the lupus-prone Fcgr2b-/- mice from developing severe kidney damage without altering anti-double stranded (ds) DNA Ab production, by simultaneously blocking the HB-EGF/EGFR and the TNF-α signaling in the kidney tissues. Unbiased transcriptome profiling of kidneys and kidney macrophages revealed that TNF-α and HB-EGF/EGFR signaling pathways are highly upregulated in Fcgr2b-/- mice; alterations that were diminished in the absence of iRhom2. Pharmacological blockade of either TNF-α or EGFR signaling protected Fcgr2b-/- mice from severe renal damage. Finally, kidneys from LN patients showed increased iRhom2 and HB-EGF expression, with interstitial HB-EGF expression significantly associated with chronicity indices. Our data suggest that activation of iRhom2/ADAM17-dependent TNF-α and EGFR signaling plays a crucial role in mediating irreversible kidney damage in LN, thereby uncovering a novel target for selective and simultaneous dual inhibition of two major pathological pathways in the effector arm of the disease.