Molecular basis for multimerization in the activation of the epidermal growth factor receptor.

Yongjian Huang,Deepti Karandur,Ehud Y Isacoff,Megan J Kaliszewski,Xiaojun Shi,Morgan Marita,Shashank Bharill,Adam W Smith,Sean M Peterson,John Kuriyan

doi:10.7554/elife.14107

Abstract

The epidermal growth factor receptor (EGFR) is activated by dimerization, but activation also generates higher-order multimers, whose nature and function are poorly understood. We have characterized ligand-induced dimerization and multimerization of EGFR using single-molecule analysis, and show that multimerization can be blocked by mutations in a specific region of Domain IV of the extracellular module. These mutations reduce autophosphorylation of the C-terminal tail of EGFR and attenuate phosphorylation of phosphatidyl inositol 3-kinase, which is recruited by EGFR. The catalytic activity of EGFR is switched on through allosteric activation of one kinase domain by another, and we show that if this is restricted to dimers, then sites in the tail that are proximal to the kinase domain are phosphorylated in only one subunit. We propose a structural model for EGFR multimerization through self-association of ligand-bound dimers, in which the majority of kinase domains are activated cooperatively, thereby boosting tail phosphorylation.

Highlights

The epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase that couples the binding of extracellular ligands, such as EGF and transforming growth factor-a (TGF-a), to the initiation of intracellular signaling pathways that control cell growth and proliferation (Kovacs et al, 2015a; Leahy, 2004; Lemmon et al, 2014)
We present an analysis of the stoichiometry of EGFR complexes before and after activation, using stepwise photobleaching of fluorescently-tagged proteins expressed in Xenopus oocytes (Chen et al, 2015; Ulbrich and Isacoff, 2007)
Our studies on the stoichiometry of EGFR show that the receptor is predominantly monomeric in the absence of EGF, at low expression levels

Summary

Introduction

The epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase that couples the binding of extracellular ligands, such as EGF and transforming growth factor-a (TGF-a), to the initiation of intracellular signaling pathways that control cell growth and proliferation (Kovacs et al, 2015a; Leahy, 2004; Lemmon et al, 2014). EGFR and one other member of the family (human epidermal growth factor receptor 4, HER4, known as ErbB4) bind to specific ligands, and respond by activating their intracellular kinase domains. The two other members of the family, HER2 and HER3, are potent signaling receptors in combination, with HER3 switching on the kinase activity of HER2 in response to ligand binding (Citri et al, 2003; Sliwkowski et al, 1994).

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