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PDBsum entry 2jit
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References listed in PDB file
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Key reference
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Title
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The t790m mutation in egfr kinase causes drug resistance by increasing the affinity for ATP.
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Authors
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C.H.Yun,
K.E.Mengwasser,
A.V.Toms,
M.S.Woo,
H.Greulich,
K.K.Wong,
M.Meyerson,
M.J.Eck.
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Ref.
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Proc Natl Acad Sci U S A, 2008,
105,
2070-2075.
[DOI no: ]
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PubMed id
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Note In the PDB file this reference is
annotated as "TO BE PUBLISHED".
The citation details given above were identified by an automated
search of PubMed on title and author
names, giving a
perfect match.
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Abstract
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Lung cancers caused by activating mutations in the epidermal growth factor
receptor (EGFR) are initially responsive to small molecule tyrosine kinase
inhibitors (TKIs), but the efficacy of these agents is often limited because of
the emergence of drug resistance conferred by a second mutation, T790M.
Threonine 790 is the "gatekeeper" residue, an important determinant of inhibitor
specificity in the ATP binding pocket. The T790M mutation has been thought to
cause resistance by sterically blocking binding of TKIs such as gefitinib and
erlotinib, but this explanation is difficult to reconcile with the fact that it
remains sensitive to structurally similar irreversible inhibitors. Here, we show
by using a direct binding assay that T790M mutants retain low-nanomolar affinity
for gefitinib. Furthermore, we show that the T790M mutation activates WT EGFR
and that introduction of the T790M mutation increases the ATP affinity of the
oncogenic L858R mutant by more than an order of magnitude. The increased ATP
affinity is the primary mechanism by which the T790M mutation confers drug
resistance. Crystallographic analysis of the T790M mutant shows how it can adapt
to accommodate tight binding of diverse inhibitors, including the irreversible
inhibitor HKI-272, and also suggests a structural mechanism for catalytic
activation. We conclude that the T790M mutation is a "generic" resistance
mutation that will reduce the potency of any ATP-competitive kinase inhibitor
and that irreversible inhibitors overcome this resistance simply through
covalent binding, not as a result of an alternative binding mode.
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Figure 1.
Chemical structures of selected EGFR inhibitors. All
compounds are drawn in a consistent orientation and conformation
that reflects their approximate binding mode in the EGFR kinase.
HKI-272 and EKB-569 are examples of irreversible inhibitors.
Lapatinib and HKI-272 are thought to require the inactive
conformation of EGFR for binding because of their additional
aniline substitutions.
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Figure 2.
Crystal structures of the EGFR T790M mutant show that
inhibitors are readily accommodated in the active and inactive
conformations of the kinase. (A) Superposition of EGFR
T790M/AEE788 complex (yellow) and WT/AEE788 complex [light blue;
drawn from PDB ID code 2J6M (8)]. Dashed lines indicate hydrogen
bonds to the kinase hinge region that are preserved in both
complexes. The location of the T790M mutation is indicated. (B)
Superposition of EGFR T790M/AEE788 complex (yellow) and
apo-T790M structure (green). Note the alternate side-chain
conformation of Met-790 in the presence of the inhibitor. (C)
Crystal structure of HKI-272 in complex with the T790M mutant.
The kinase adopts an inactive conformation, with the C-helix
displaced. A covalent bond is formed between Cys-797 and the
crotonamide Michael acceptor of HKI-272. (D) The structure of
the T790M mutant in complex with HKI-272 (yellow) is
superimposed on the structure of the WT EGFR kinase in complex
with Lapatinib [light blue; drawn from PDB ID code 1XKK (32)].
In both structures, the kinase adopts the same inactive
conformation and the inhibitors bind in a similar manner, with a
single hydrogen bond to the hinge (dashed lines) and with their
aniline substituents extending into the enlarged hydrophobic
pocket that is characteristic of the inactive conformation.
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