Epidermal Growth Factor Receptor(EGFR) signaling pathway Samantha 03/09/11 Outline • • • • EGFR signaling pathway EGFR endocytosis Crosstalk Clinic therapy The significant of EGFR signaling pathway http://www.informedicalcme.com/egfr/tyrosine-kinase-inhibitors-sensitivity/ EGFR signaling pathway • EGF Receptors • Downstream of EGFR • A new role for Egfr in cancer The discovery of epidermal growth factor http://nobelprize.org/nobel_prizes/medicine/laureates/1986/press.html The discovery of epidermal growth factor http://nobelprize.org/nobel_prizes/medicine/laureates/1986/press.html EGF Receptor Members Table 15-4 Molecular Biology of the Cell (© Garland Science 2008) EGF Receptor Members EGF receptor members: Vertibrates: EGFR; ErbB2; ErbB3; ErbB4 C. elegans: Let-23 Drosophila: DER C. elegans and Drosophila have served as useful model systems for studying the signaling processes triggered by the EGF receptor. Recall: RTKs have 3 functional regions: 1. N-terminal extracellular region w/ 1 or more ligand-binding sites 2. Single transmembrane -helix domain 3. C-terminal cytoplasmic region w/ catalytic domain + phosphorylation sites Lodish (2004) Fig 14-5 EGF receptor structure ErbB3--has impaired kinase activity, and only signals when heterodimerizing with another receptor type. Bogdan et al. 2000 EGF receptor structure Eigenbrot et al; Activation of the EGF receptor Ligands: Spices Ligands ErbB2 doesn’t bind Lin-3, any EGFC. elegans a soluble TGFa-like ligand. like ligands on its own, Drosophila Spitz, Vein, Grken, Keren but can heterodimerize Human More than dozen ligands with other EGF-bound receptors. ErbB3 has impaired kinase activity, and only signals when heterodimerizing with another receptor type. Roepstorff et al.2008 Recall: Receptor tyrosine kinase activation by dimerization only transphosphorylation Lodish (2004) Fig 14-5 cis- &/or transphosphorylation Activation of the EGF receptor In the cytoplasm, the two tyrosine kinase domains form an asymmetric dimer, with the c-terminal lobe. Juxtamembrane region of EGFR stabilizes formation of the asymmetric kinase dimer. EGFR is not activated by autophosphorylation of the activation loop. Hubbard et al. (2009) Downstream of EGFR Bogdan et al. 2000 Downstream of EGFR SIGMA-ALDRICH Negative regulator of EGFR signaling Bogdan et al. 2000 Recall: Models of Signaling in Membrane Rafts Simons & Toomre 2000 Model 1a: - raft-associated receptors activated by dimerization. Model 1b: - dimerization increases affinity for raft. Model 2: - clustering of multiple rafts triggers signaling Lipid rafts and EGFR methyl-B-cyclodextrin cholesterol depletion inhibition of EGF-stimulated PI turnover. BUT, led to an enhancement of EGF-stimulated MAP kinase activity. Lipid rafts disruption appears to have both positive and negative effects on receptor tyrosine kinase-mediated signaling Lipid rafts and EGFR methyl-B-cyclodextrin cholesterol depletion The enhancement of EGF binding and receptor autophosphorylation An increase in intrinsic receptor kinase activity . EGF receptor function is suppressed when the receptor is localized to lipid rafts. A new role of Egfr as a transcription factor Wen, 2010 A new role of Egfr in cancer Engelman etal. 2008 Outline • • • • EGFR signaling pathway EGFR endocytosis Crosstalk Clinic therapy EGFR endocytosis • Ligand-induced endocytosis of EGFR • Novel way of EGFR endocytosis Negative regulator of EGFR signaling Bogdan et al. 2000 Clathrin-mediated EGFR endocytosis Grb-dependent pathway: Grb2-Cb1 complex is recruited to C-terminal of EGFR. Adds mono-or polyubiquitins to EGFR. Activated EGFR is transported to clathrin coated pits. Roepstorff et al. 2008 Clathrin-mediated EGFR endocytosis Grb-independent pathway Cb1 can mediate ubiquination of “X” internalization of EGFR. EGFR can directly interact with AP-2 Sorkin et al.2008 Clathrin-mediated EGFR endocytosis A, EGFR is recycled back to the plasma membrane. B, EGFR will be degraded in lysosomes. Clathrin-mediated EGFR endocytosis & signaling Signal transduction Membrane trafficking Signal transduction molecules affect membrane trafficking. Membrane trafficking can regulate signal transduction events. The initial phase of EGFR signaling is endocyotosis-independent, but Later events require clathrin-mediated EGFR Endocytosis(CME). AKT and ERK require CME, EGFR-activated DNA synthesis depends on functional CME. Clathrin-independent EGFR endocytosis Under conditions of receptor overexpression and/or high ligand concentrations, clathrin-independent internalization determines the overall rate of the EGFR uptake into the cell A-431 cells Formation of micro-and macropinocytic vesiles COS cells Large vesicular structures Several types of cells Vesicular-tubular endocytic compartment originated from the plasma membrane dorsal ruffles The novel function of EGFR dimerization in internalization Inhibition of EGFR kinase activation did not block EGF-induced EGFR internalization. Absence of EGFR dimerization, EGF binding can not stimulate EGFR endocytosis. EGFR dimerization can mediate the EGF-induced cellular process independently of its role in activating EGFR tyrosien kinase. Outline • • • • EGFR signaling pathway EGFR endocytosis Crosstalk Clinic therapy Cross-talk • • • • EGFR signaling and Notch pathway EGFR signaling and GPCR EGFR and Wnt signaling EGF and insulin cell signaling pathway EGFR signaling and Notch pathway Hasson and Paroush, 2006 EGFR signaling and GPCR Prenzel et al .2000 EGFR and Wnt signaling EGF and insulin cell signaling pathway Outline • • • • EGFR signaling pathway EGFR endocytosis Crosstalk Clinic therapy Clinic therapy • EGFR inhibitor • New possible therapies Clinic Therapy • Monoclonal antibodies (mAbs)directed against the EGFR extracellular domain • Small molecule tyrosine kinase inhibitors (TKIs)directed against the tyrosine kinase domain. EGFR inhibitor Natural inhibitors include potato carboxypeptidase inhibitor(PCI), which contains a small cysteinerich module, called a T-knot scaffold, that is shared by several different protein families, including the EGF family. https://www. medscape.com New possible therapies • Nuclear EGFR and EGFR-targeted Therapy • Therapy based on EGFR kinase-indepenent activity References • • • • • • • • 1, Robert N.Jorissen, Francesca Walker, Normand Pouliot , Thomas P.J.Garrett, Colin W. Ward, and Antony W.Burgess. Epidermal growth factor receptor: mechanisms of activation and signaling. Experimental Cell Research 284(2003)31-53. 2, Sven Bogdan and Christian Klambt. Epidermal growth factor receptor signaling. Current Biology (2000) Vol10 No8. 3, Shiaw-Yih Lin, Keishi Makino, Weiya Xia, Angabin Matin, Yong Wen, Ka Yin Kwong, Lilly Bourguignon and Mien-Chie Hung. Nuclear localization of EGF receptor and its potential new role as a transcription factor. 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