Elucidation of a four-site allosteric network in fibroblast growth factor receptor tyrosine kinases.

Huaibin Chen,Weiming Gai,Moosa Mohammadi,Jingjing Deng,William M Marsiglia,Thomas A Neubert,Shibani Bhattacharya,Zhifeng Huang,Nathaniel J Traaseth,Min-Kyu Cho,Steven P Blais

doi:10.7554/elife.21137

Huaibin Chen, Weiming Gai + Show 9 more

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https://doi.org/10.7554/elife.21137

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Abstract

Receptor tyrosine kinase (RTK) signaling is tightly regulated by protein allostery within the intracellular tyrosine kinase domains. Yet the molecular determinants of allosteric connectivity in tyrosine kinase domain are incompletely understood. By means of structural (X-ray and NMR) and functional characterization of pathogenic gain-of-function mutations affecting the FGF receptor (FGFR) tyrosine kinase domain, we elucidated a long-distance allosteric network composed of four interconnected sites termed the 'molecular brake', 'DFG latch', 'A-loop plug', and 'αC tether'. The first three sites repress the kinase from adopting an active conformation, whereas the αC tether promotes the active conformation. The skewed design of this four-site allosteric network imposes tight autoinhibition and accounts for the incomplete mimicry of the activated conformation by pathogenic mutations targeting a single site. Based on the structural similarity shared among RTKs, we propose that this allosteric model for FGFR kinases is applicable to other RTKs.

Highlights

Receptor tyrosine kinase (RTK) signaling fulfills fundamental functions in development, tissue homeostasis, and metabolism of metazoan organisms (Manning et al, 2002)
Other RTK subfamilies require trans-phosphorylation on regulatory tyrosines located in the activation loop (Aloop) in order to trigger activation
Through crystallographic and solution NMR analyses of five pathogenic FGFR2 kinases at a conserved lysine in the A-loop, we showed that these mutations introduce additional hydrogen bonding or hydrophobic contacts to differentially stabilize the active conformation of the A-loop (Chen et al, 2013) in a dynamic two-state equilibrium regimen

Summary

Introduction

Receptor tyrosine kinase (RTK) signaling fulfills fundamental functions in development, tissue homeostasis, and metabolism of metazoan organisms (Manning et al, 2002). The 58 human RTKs are divided into ~17 subfamilies, each featuring unique architectures in their extracellular domain that are specialized to bind and mediate the biological actions of distinct growth factors, cytokines and hormones such as EGF, FGF, PDGF, VEGF, IGF, insulin and NGF (Lemmon and Schlessinger, 2010). The divergent extracellular domains of RTK subfamilies are linked via a single transmembrane helix to the intracellular domain that harbors the conserved tyrosine kinase domain. Despite exhibiting major structural diversity in their ectodomains, all RTKs must rely on the universal process of ligandinduced dimerization or rearrangement of preformed dimers to elevate the intrinsic activity of the intracellular kinase domain (Lemmon and Schlessinger, 2010). Analysis of crystal structures of unphosphorylated receptor tyrosine kinase domains representing every RTK subfamily show that in the resting state (i.e. in the absence of extracellular ligand engagement) kinase domains are autoinhibited through a variety of

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