Conserved roles for receptor tyrosine kinase extracellular regions in regulating receptor and pathway activity.

Monica Gonzalez-Magaldi,Haley N Cartwright,Daniel J Leahy,Jacqueline M Mccabe,Ningze Sun

doi:10.1042/bcj20200702

Monica Gonzalez-Magaldi, Haley N Cartwright + Show 3 more

Open Access

https://doi.org/10.1042/bcj20200702

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Abstract

Receptor Tyrosine Kinases (RTKs) comprise a diverse group of cell-surface receptors that mediate key signaling events during animal development and are frequently activated in cancer. We show here that deletion of the extracellular regions of 10 RTKs representing 7 RTK classes or their substitution with the dimeric immunoglobulin Fc region results in constitutive receptor phosphorylation but fails to result in phosphorylation of downstream signaling effectors Erk or Akt. Conversely, substitution of RTK extracellular regions with the extracellular region of the Epidermal Growth Factor Receptor (EGFR) results in increases in effector phosphorylation in response to EGF. These results indicate that the activation signal generated by the EGFR extracellular region is capable of activating at least seven different RTK classes. Failure of phosphorylated Fc-RTK chimeras or RTKs with deleted extracellular regions to stimulate phosphorylation of downstream effectors indicates that either dimerization and receptor phosphorylation per se are insufficient to activate signaling or constitutive dimerization leads to pathway inhibition.

Highlights

Receptor Tyrosine Kinases (RTKs) are Type I cell-surface proteins that consist of an extracellular ligand-binding region, a membrane-spanning helix, and a tyrosine kinasecontaining intracellular region (Lemmon & Schlessinger, 2010)
To investigate the role of RTK extracellular regions (ECRs) in regulating RTK activity and the extent to which activation mechanisms are shared between different RTK classes, we examined the behavior of representatives of the Epidermal Growth Factor Receptor (EGFR), InsR, Fibroblast Growth Factors (FGFs) Receptor (FGFR), Vascular Endothelial Growth Factor (VEGF) Receptor (VEGFR), Nerve Growth Factor (NGF) Receptor (Trk), Platelet-derived GrowthFactor (PDGF) Receptor (PDGFR), and Met (Met and Ron) classes of RTK with deleted or substituted ECRs (Table 1)
Deletions or mutations in several RTK extracellular regions have been associated with increased receptor phosphorylation, which has been interpreted as indicating an autoinhibitory role for these ECRs

Summary

Introduction

Receptor Tyrosine Kinases (RTKs) are Type I cell-surface proteins that consist of an extracellular ligand-binding region, a membrane-spanning helix, and a tyrosine kinasecontaining intracellular region (Lemmon & Schlessinger, 2010). 2001; Nagy, Claus, Jovin, & Arndt-Jovin, 2010; Saffarian, Li, Elson, & Pike, 2007; Zhang, Gureasko, Shen, Cole, & Kuriyan, 2006) Most notable in this respect are members of the Insulin Receptor (InsR) family, the subunits of which form disulfide-linked dimers and have long been thought to signal via a ligand-dependent conformational change To investigate the role of RTK extracellular regions (ECRs) in regulating RTK activity and the extent to which activation mechanisms are shared between different RTK classes, we examined the behavior of representatives of the EGFR, InsR, FGF Receptor (FGFR), VEGF Receptor (VEGFR), NGF Receptor (Trk), PDGF Receptor (PDGFR), and Met (Met and Ron) classes of RTK with deleted or substituted ECRs (Table 1). ECRs generate a conserved activation signal and that constitutive phosphorylation of RTKs either leads to feedback inhibition of downstream effectors or an ECR generated signal in addition to dimerization is needed to couple receptor phosphorylation to pathway activation

Results

Discussion

Declaration of Interests

Materials and Methods