Key Event Title
|Level of Biological Organization|
|epithelial cell of lung|
Key Event Components
|epidermal growth factor-activated receptor activity||epidermal growth factor receptor||occurrence|
Key Event Overview
AOPs Including This Key Event
|AOP Name||Role of event in AOP|
|Decreased lung function||MolecularInitiatingEvent|
Key Event Description
The EGF receptor family comprises 4 members, EGFR (also referred to as ErbB1/HER1), ErbB2/Neu/HER2, ErbB3/HER3 and ErbB4/HER4, all of which are transmembrane glycoproteins with an extracellular ligand binding site and an intracellular tyrosine kinase domain. Receptor-ligand binding induces dimerization and internalization, subsequently leading to activation of the receptor through autophosphorylation (Higashiyama et al., 2008).
EGFR signaling is central to airway epithelial maintenance and mucin production (Burgel and Nadel, 2004), and EGFR expression has been demonstrated in lung epithelial cells under physiological (albeit weakly) as well as pathological conditions in vitro and in vivo (Aida et al., 1994; Burgel and Nadel, 2008; O’Donnell et al., 2004; Polosa et al., 1999). Of note, lung epithelial EGFR phosphorylation was increased under conditions of oxidative stress including exposure to H2O2 (Goldkorn et al., 1998), naphthalene (Van Winkle et al., 1997), cigarette smoke (de Boer et al., 2006; Marinaş et al., 2011) and in the presence of neutrophils or neutrophil elastase (Kohri et al., 2002; Shao et al., 2004; Shao and Nadel, 2005; Shim et al., 2001; Takeyama et al., 2000). EGFR activation by oxidative stress may have a number of root causes: ROS were shown to increase production of EGF, the prime EGFR ligand, by lung epithelial cells (Casalino-Matsuda et al., 2004). Similarly, expression and secretion of TGF-α and AREG, also EGFR ligands, were elevated in human bronchial epithelial cells in response to fine particulate matter (PM2.5), diesel particulate matter and cigarette smoke exposure (Blanchet et al., 2004; Lemjabbar et al., 2003; Rumelhard et al., 2007). Mechanistically, this process is dependent on ROS-mediated activation of metalloproteinases or ADAMs which cleave membrane-bound EGFR ligand precursors, making them locally available to bind to and transactivate EGFR in an autocrine manner (Deshmukh et al., 2009; Kim et al., 2004b; Val et al., 2012; Yoshisue and Hasegawa, 2004). Furthermore, ligand binding to EGFR itself was shown to lead to H2O2 production, thereby facilitating receptor activation and downstream signaling (DeYulia et al., 2005; DeYulia Jr. and Cárcamo, 2005; Truong and Carroll, 2012). While it is tempting to speculate that the increase in H2O2 would perpetuate EGFR activation via the continuous proteolytic shedding of pro-ligands in an autocrine loop, multiple lines of evidence suggest that oxidative modification, specifically EGFR sulfenylation, contributes to enhanced tyrosine phosphorylation of the receptor and downstream signaling (Paulsen et al., 2011; Ravid et al., 2002; Truong and Carroll, 2012; Truong et al., 2016).
Classical EGFR downstream signaling involves activation of Ras which subsequently initiates signal transduction through the Raf-1/MEK/ERK pathway. MAP kinase activation in turn promotes airway epithelial cell proliferation and differentiation (Hackel et al., 1999; Kim et al., 2005; Lemjabbar et al., 2003) and facilitates epithelial wound repair (Allahverdian et al., 2010; Burgel and Nadel, 2004; Van Winkle et al., 1997).
How It Is Measured or Detected
Proof of EGFR activation can be derived from Western blots of e.g. untreated and treated cell or tissue lysates using specific antibodies targeting the phosphorylated EGFR epitopes. Densitometric evaluation of the colorimetrically stained, chemiluminescent or radioactive bands on the blot then permit a (semi-)quantitative measure of activation. Moreover, the addition of EGFR inhibitors such as AG1478 and BIBX 1522 or neutralizing antibodies is well suited to demonstrate causality.
Domain of Applicability
EGFR activation in human, mouse and rat is well documented, and EGF ligands and EGFR are orthologous within these species. EGFR is a driver of human cancer in various tissues and numerous drugs are approved that inhibit EGFR activation (Ciardiello and Tortora, 2008). Although EGFR and its ligands are expressed in human, mouse and rat (Chen et al., 2007), species differences have been noted in binding and structure (Nexø and Hansen, 1985), and even can have opposite downstream effects in mouse and rat (Kiley and Chevalier, 2007).
Evidence for Perturbation by Stressor
Overview for Molecular Initiating Event
Aida, S., et al., Distribution of epidermal growth factor and epidermal growth factor receptor in human lung: immunohistochemical and immunoelectron-microscopic studies. Respiration, 1994. 61(3): p. 161-166.
Allahverdian, S., et al., Sialyl Lewis X modification of the epidermal growth factor receptor regulates receptor function during airway epithelial wound repair. Clinical & Experimental Allergy, 2010. 40(4): p. 607-618.
Blanchet, S., et al., Fine particulate matter induces amphiregulin secretion by bronchial epithelial cells. American Journal of Respiratory Cell and Molecular Biology, 2004. 30(4): p. 421-427.
Burgel, P.-R. and J.A. Nadel, Epidermal growth factor receptor-mediated innate immune responses and their roles in airway diseases. European Respiratory Journal, 2008. 32(4): p. 1068-1081.
Ciardiello, F., and Tortora, G. (2008). EGFR antagonists in cancer treatment. N. Engl. J. Med. 358, 1160–1174.
Casalino-Matsuda, S.M., et al., Role of hyaluronan and reactive oxygen species in tissue kallikrein-mediated epidermal growth factor receptor activation in human airways. Journal of Biological Chemistry, 2004. 279(20): p. 21606-21616.
Chen, H., Liu, B., & Neufeld, A. H. (2007). Epidermal growth factor receptor in adult retinal neurons of rat, mouse, and human. Journal of Comparative Neurology, 500(2), 299-310.
de Boer, W.I., et al., Expression of epidermal growth factors and their receptors in the bronchial epithelium of subjects with chronic obstructive pulmonary disease. American Journal of Clinical Pathology, 2006. 125(2): p. 184-192.
Deshmukh, H.S., et al., Matrix metalloproteinase-14 mediates a phenotypic shift in the airways to increase mucin production. Am J Respir Crit Care Med, 2009. 180(9): p. 834-845.
DeYulia, G.J., et al., Hydrogen peroxide generated extracellularly by receptor–ligand interaction facilitates cell signaling. Proceedings of the National Academy of Sciences of the United States of America, 2005. 102(14): p. 5044-5049.
DeYulia Jr., G.J. and J.M. Cárcamo, EGF receptor-ligand interaction generates extracellular hydrogen peroxide that inhibits EGFR-associated protein tyrosine phosphatases. Biochem Biophys Res Commun, 2005. 334(1): p. 38-42.
Goldkorn, T., et al., EGF-receptor phosphorylation and signaling are targeted by H2O2 redox stress. American Journal of Respiratory Cell and Molecular Biology, 1998. 19(5): p. 786-798.
Hackel, P.O., et al., Epidermal growth factor receptors: critical mediators of multiple receptor pathways. Current Opinion in Cell Biology, 1999. 11(2): p. 184-189.
Higashiyama, S., et al., Membrane-anchored growth factors, the epidermal growth factor family: Beyond receptor ligands. Cancer Science, 2008. 99(2): p. 214-220.
Jorissen, R.N., Walker, F., Pouliot, N., Garrett, T.P.J., Ward, C.W., and Burgess, A.W. (2003). Epidermal growth factor receptor: mechanisms of activation and signalling. Exp. Cell Res. 284, 31–53.
Kiley, S.C., and Chevalier, R.L. (2007). Species differences in renal Src activity direct EGF receptor regulation in life or death response to EGF. Am. J. Physiol. Renal Physiol. 293, F895–F903.
Kim, J.H., et al., Effects of matrix metalloproteinase inhibitor on LPS-induced goblet cell metaplasia. American Journal of Physiology - Lung Cellular and Molecular Physiology, 2004. 287(1): p. L127-L133.
Kim, S., A.J. Schein, and J.A. Nadel, E-cadherin promotes EGFR-mediated cell differentiation and MUC5AC mucin expression in cultured human airway epithelial cells. American Journal of Physiology - Lung Cellular and Molecular Physiology, 2005. 289(6): p. L1049-L1060.
Kohri, K., I.F. Ueki, and J.A. Nadel, Neutrophil elastase induces mucin production by ligand-dependent epidermal growth factor receptor activation. Am J Physiol Lung Cell Mol Physiol, 2002. 283(3): p. L531-40.
Lemjabbar, H., et al., Tobacco smoke-induced lung cell proliferation mediated by tumor necrosis factor alpha-converting enzyme and amphiregulin. J Biol Chem, 2003. 278(28): p. 26202-7.
Marinaş, A., et al., Expression of Epidermal Growth Factor (EGF) and its receptors (EGFR1 and EGFR2) in chronic bronchitis. Romanian journal of morphology and embryology= Revue roumaine de morphologie et embryologie, 2011. 53(4): p. 957-966.
Nexø, E., and Hansen, H.F. (1985). Binding of epidermal growth factor from man, rat and mouse to the human epidermal growth factor receptor. Biochim. Biophys. Acta 843, 101–106.
O’Donnell, R., et al., Expression of ErbB receptors and mucins in the airways of long term current smokers. Thorax, 2004. 59(12): p. 1032-1040.
Paulsen, C.E., et al., Peroxide-dependent sulfenylation of the EGFR catalytic site enhances kinase activity. Nat Chem Biol, 2011. 8(1): p. 57-64.
Polosa, R., et al., Expression of c-erbB receptors and ligands in human bronchial mucosa. American Journal of Respiratory Cell and Molecular Biology, 1999. 20(5): p. 914-923.
Ravid, T., et al., Epidermal growth factor receptor activation under oxidative stress fails to promote c-Cbl mediated down-regulation. Journal of Biological Chemistry, 2002. 277(34): p. 31214-31219.
Rumelhard, M., et al., Expression and role of EGFR ligands induced in airway cells by PM2.5 and its components. European Respiratory Journal, 2007. 30(6): p. 1064-1073.
Shao, M.X.G., Nakanaga, T., and Nadel, J.A. (2004). Cigarette smoke induces MUC5AC mucin overproduction via tumor necrosis factor-alpha-converting enzyme in human airway epithelial (NCI-H292) cells. Am. J. Physiol. Lung Cell. Mol. Physiol. 287, L420–L427.
Shao, M.X.G. and J.A. Nadel, Neutrophil Elastase Induces MUC5AC Mucin Production in Human Airway Epithelial Cells via a Cascade Involving Protein Kinase C, Reactive Oxygen Species, and TNF-α-Converting Enzyme. The Journal of Immunology, 2005. 175(6): p. 4009-4016.
Shim, J.J., et al., IL-13 induces mucin production by stimulating epidermal growth factor receptors and by activating neutrophils. Am J Physiol Lung Cell Mol Physiol, 2001. 280(1): p. L134-40.
Takeyama, K., et al., Oxidative stress causes mucin synthesis via transactivation of epidermal growth factor receptor: role of neutrophils. J Immunol, 2000. 164(3): p. 1546-1552.
Truong, T.H. and K.S. Carroll, Redox regulation of EGFR signaling through cysteine oxidation. Biochemistry, 2012. 51(50): p. 9954-9965.
Truong, T.H., et al., Molecular basis for redox activation of epidermal growth factor receptor kinase. Cell Chemical Biology, 2016. 23(7): p. 837-848.
Val, S., et al., Fine PM induce airway MUC5AC expression through the autocrine effect of amphiregulin. Archives of Toxicology, 2012. 86(12): p. 1851-1859.
Van Winkle, L.S., J.M. Isaac, and C.G. Plopper, Distribution of epidermal growth factor receptor and ligands during bronchiolar epithelial repair from naphthalene-induced Clara cell injury in the mouse. The American journal of pathology, 1997. 151(2): p. 443.
Yoshisue, H. and K. Hasegawa, Effect of MMP/ADAM inhibitors on goblet cell hyperplasia in cultured human bronchial epithelial cells. Biosci Biotechnol Biochem, 2004. 68(10): p. 2024-2031.