Dataset Information

Flotillin-2 regulates EGFR activation, degradation, and cancer growth

ABSTRACT: 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.

INSTRUMENT(S): LTQ Orbitrap

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Epithelial Cell

DISEASE(S): Disease Free

SUBMITTER: Xu Zhang

LAB HEAD: Stanley Lipkowitz

PROVIDER: PXD031988 | Pride | 2023-03-11

REPOSITORIES: Pride

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Publications

Flotillin-2 regulates epidermal growth factor receptor activation, degradation by Cbl-mediated ubiquitination, and cancer growth.

Wisniewski David J DJ Liyasova Mariya S MS Korrapati Soumya S Zhang Xu X Ratnayake Shashikala S Chen Qingrong Q Gilbert Samuel F SF Catalano Alexis A Voeller Donna D Meerzaman Daoud D Guha Udayan U Porat-Shliom Natalie N Annunziata Christina M CM Lipkowitz Stanley S

The Journal of biological chemistry 20221205 1

Epidermal growth factor receptor (EGFR) signaling is frequently dysregulated in various cancers. The ubiquitin ligase Casitas B-lineage lymphoma proto-oncogene (Cbl) regulates degradation of activated EGFR through ubiquitination and acts as an adaptor to recruit proteins required for trafficking. Here, we used stable isotope labeling with amino acids in cell culture mass spectrometry to compare Cbl complexes with or without epidermal growth factor (EGF) stimulation. We identified over a hundred ...[more]

PMID: 36470425

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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: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.

Dataset Information

Flotillin-2 regulates EGFR activation, degradation, and cancer growth

Publications

Flotillin-2 regulates epidermal growth factor receptor activation, degradation by Cbl-mediated ubiquitination, and cancer growth.

Similar Datasets

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