An Allosteric Mechanism for Activation of the Kinase Domain of Epidermal Growth Factor Receptor

Abstract

The mechanism by which the epidermal growth factor receptor (EGFR) is activated upon dimerization has eluded definition. We find that the EGFR kinase domain can be activated by increasing its local concentration or by mutating a leucine (L834R) in the activation loop, the phosphorylation of which is not required for activation. This suggests that the kinase domain is intrinsically autoinhibited, and an intermolecular interaction promotes its activation. Using further mutational analysis and crystallography we demonstrate that the autoinhibited conformation of the EGFR kinase domain resembles that of Src and cyclin-dependent kinases (CDKs). EGFR activation results from the formation of an asymmetric dimer in which the C-terminal lobe of one kinase domain plays a role analogous to that of cyclin in activated CDK/cyclin complexes. The CDK/cyclin-like complex formed by two kinase domains thus explains the activation of EGFR-family receptors by homo- or heterodimerization.

EGF-independent activation of cell-surface EGF receptors harboring mutations found in gefitinib-sensitive lung cancer

“…We show that the active mutated receptors are present (and active) at the cell surface. In investigations of the mechanistic basis for EGFR activation by NSCLC mutations, we also found that simply disrupting autoinhibitory interactions observed crystallographically in the tyrosine kinase domain (Wood et al, 2004;Zhang et al, 2006) is sufficient to generate similar constitutively active variants of EGFR.…”

“…Recent structural studies provide potential mechanistic explanations for how gefitinib-sensitizing mutations elevate EGF-independent EGFR kinase activity (Wood et al, 2004;Zhang et al, 2006). In the inactive conformation of the EGFR tyrosine kinase domain with bound lapatinib (Wood et al, 2004) or AMP-PNP (Zhang et al, 2006), the aC helix and the activation loop interact directly with one another.…”

Autophosphorylation of the carboxyl‐terminal domain is not required for oncogenic transformation by lung‐cancer derived EGFR mutants

“…Ligand‐induced dimerization of the receptor's extracellular domain leads to approximation of the intracellular domains, followed by asymmetric dimerization of the two kinase domains, where the C‐lobe of one kinase domain (the “activator” monomer) binds to the N‐lobe of the second kinase domain (the “receiver” monomer) and allosterically activates it 11. Following these receptor dimerization events, EGFR becomes fully activated and undergoes phosphorylation at multiple tyrosine residues within its C‐terminal tail.…”

Phosphorylation of RAF Kinase Dimers Drives Conformational Changes that Facilitate Transactivation

“…In PKA, CDK2, and p38 structures, the R‐spine and the corresponding Trp do not interact. Although this Trp is not conserved in EGFR, crystal structures show that its functional equivalent lysine (L680)18 also interacts with the R‐spine. Remarkably, mutation of L680 destabilizes the EGFR dimer in the active complex and impedes kinase activity 18.…”

“…Although this Trp is not conserved in EGFR, crystal structures show that its functional equivalent lysine (L680)18 also interacts with the R‐spine. Remarkably, mutation of L680 destabilizes the EGFR dimer in the active complex and impedes kinase activity 18. We observed that the NtA motif together with W450 extends the dimerization interface, thereby connecting the R‐spines and thus the distant active sites of the two protomers.…”