Limits...
Crystal structure of the FLT3 kinase domain bound to the inhibitor Quizartinib (AC220).

Zorn JA, Wang Q, Fujimura E, Barros T, Kuriyan J - PLoS ONE (2015)

Bottom Line: This conformation is similar to that observed for the uncomplexed intracellular domain of FLT3 as well as for related receptor tyrosine kinases, except for a localized induced fit in the activation loop.The co-crystal structure reveals the interactions between quizartinib and the active site of FLT3 that are key for achieving its high potency against both wild-type FLT3 as well as a FLT3 variant observed in many AML patients.This co-complex further provides a structural rationale for quizartinib-resistance mutations.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America; California Institute for Quantitative Biosciences, University of California, Berkeley, California, United States of America.

ABSTRACT
More than 30% of acute myeloid leukemia (AML) patients possess activating mutations in the receptor tyrosine kinase FMS-like tyrosine kinase 3 or FLT3. A small-molecule inhibitor of FLT3 (known as quizartinib or AC220) that is currently in clinical trials appears promising for the treatment of AML. Here, we report the co-crystal structure of the kinase domain of FLT3 in complex with quizartinib. FLT3 with quizartinib bound adopts an "Abl-like" inactive conformation with the activation loop stabilized in the "DFG-out" orientation and folded back onto the kinase domain. This conformation is similar to that observed for the uncomplexed intracellular domain of FLT3 as well as for related receptor tyrosine kinases, except for a localized induced fit in the activation loop. The co-crystal structure reveals the interactions between quizartinib and the active site of FLT3 that are key for achieving its high potency against both wild-type FLT3 as well as a FLT3 variant observed in many AML patients. This co-complex further provides a structural rationale for quizartinib-resistance mutations.

No MeSH data available.


Related in: MedlinePlus

The juxtamembrane segment of FLT3 clashes with quizartinib.(A) An overlay of the FLT3:quizartinib crystal structure (color scheme depicted in Fig 1A) with the autoinhibited FLT3 (shown in grey, PDB 1RJB). The zoomed-in view of the juxtamembrane segment highlights clashes between the juxtamembrane segment and quizartinib. (B) An overlay of the crystal structure of the VEGFR2 kinase domain bound to sorafenib (shown in red/ blue, PDB 4ASD) and the VEGFR2 kinase domain bound to axitinib (shown in grey, PDB 4AGC). Only sorafenib is illustrated in the active site for clarity. The juxtamembrane segment from the VEGFR2:sorafenib co-crystal structure is shown in orange and is extended away from the active site. The juxtamembrane segment from the VEGFR:axitinib co-crystal structure remains bound to the kinase domain. The detailed view illustrates similar clashes between sorafenib and the VEGFR2 bound conformation of the juxtamembrane segment.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4383440&req=5

pone.0121177.g005: The juxtamembrane segment of FLT3 clashes with quizartinib.(A) An overlay of the FLT3:quizartinib crystal structure (color scheme depicted in Fig 1A) with the autoinhibited FLT3 (shown in grey, PDB 1RJB). The zoomed-in view of the juxtamembrane segment highlights clashes between the juxtamembrane segment and quizartinib. (B) An overlay of the crystal structure of the VEGFR2 kinase domain bound to sorafenib (shown in red/ blue, PDB 4ASD) and the VEGFR2 kinase domain bound to axitinib (shown in grey, PDB 4AGC). Only sorafenib is illustrated in the active site for clarity. The juxtamembrane segment from the VEGFR2:sorafenib co-crystal structure is shown in orange and is extended away from the active site. The juxtamembrane segment from the VEGFR:axitinib co-crystal structure remains bound to the kinase domain. The detailed view illustrates similar clashes between sorafenib and the VEGFR2 bound conformation of the juxtamembrane segment.

Mentions: While the autoinhibited FLT3 (PDB 1RJB) and the co-crystal structure of FLT3 with quizartinib both adopt an inactive “Abl-like” structure, one distinct feature is the absence of the juxtamembrane segment in the co-crystal structure. This segment was included in the crystallization construct, but no interpretable electron density is visible for it. A superposition of the juxtamembrane segment from the autoinhibited structure onto the quizartinib-FLT3 co-complex illustrates that quizartinib binding is not compatible with the juxtamembrane segment being folded onto the kinase domain (Fig 5A). This superposition indicates that Leu 576 on the juxtamembrane segment would clash with quizartinib. Notably, the conformation of the juxtamembrane segment in the autoinhibited FLT3 (PDB 1RJB) structure would not be compatible with the crystal packing in the FLT3:quizartinib structure, which may also contribute to the lack of electron density for this region.


Crystal structure of the FLT3 kinase domain bound to the inhibitor Quizartinib (AC220).

Zorn JA, Wang Q, Fujimura E, Barros T, Kuriyan J - PLoS ONE (2015)

The juxtamembrane segment of FLT3 clashes with quizartinib.(A) An overlay of the FLT3:quizartinib crystal structure (color scheme depicted in Fig 1A) with the autoinhibited FLT3 (shown in grey, PDB 1RJB). The zoomed-in view of the juxtamembrane segment highlights clashes between the juxtamembrane segment and quizartinib. (B) An overlay of the crystal structure of the VEGFR2 kinase domain bound to sorafenib (shown in red/ blue, PDB 4ASD) and the VEGFR2 kinase domain bound to axitinib (shown in grey, PDB 4AGC). Only sorafenib is illustrated in the active site for clarity. The juxtamembrane segment from the VEGFR2:sorafenib co-crystal structure is shown in orange and is extended away from the active site. The juxtamembrane segment from the VEGFR:axitinib co-crystal structure remains bound to the kinase domain. The detailed view illustrates similar clashes between sorafenib and the VEGFR2 bound conformation of the juxtamembrane segment.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4383440&req=5

pone.0121177.g005: The juxtamembrane segment of FLT3 clashes with quizartinib.(A) An overlay of the FLT3:quizartinib crystal structure (color scheme depicted in Fig 1A) with the autoinhibited FLT3 (shown in grey, PDB 1RJB). The zoomed-in view of the juxtamembrane segment highlights clashes between the juxtamembrane segment and quizartinib. (B) An overlay of the crystal structure of the VEGFR2 kinase domain bound to sorafenib (shown in red/ blue, PDB 4ASD) and the VEGFR2 kinase domain bound to axitinib (shown in grey, PDB 4AGC). Only sorafenib is illustrated in the active site for clarity. The juxtamembrane segment from the VEGFR2:sorafenib co-crystal structure is shown in orange and is extended away from the active site. The juxtamembrane segment from the VEGFR:axitinib co-crystal structure remains bound to the kinase domain. The detailed view illustrates similar clashes between sorafenib and the VEGFR2 bound conformation of the juxtamembrane segment.
Mentions: While the autoinhibited FLT3 (PDB 1RJB) and the co-crystal structure of FLT3 with quizartinib both adopt an inactive “Abl-like” structure, one distinct feature is the absence of the juxtamembrane segment in the co-crystal structure. This segment was included in the crystallization construct, but no interpretable electron density is visible for it. A superposition of the juxtamembrane segment from the autoinhibited structure onto the quizartinib-FLT3 co-complex illustrates that quizartinib binding is not compatible with the juxtamembrane segment being folded onto the kinase domain (Fig 5A). This superposition indicates that Leu 576 on the juxtamembrane segment would clash with quizartinib. Notably, the conformation of the juxtamembrane segment in the autoinhibited FLT3 (PDB 1RJB) structure would not be compatible with the crystal packing in the FLT3:quizartinib structure, which may also contribute to the lack of electron density for this region.

Bottom Line: This conformation is similar to that observed for the uncomplexed intracellular domain of FLT3 as well as for related receptor tyrosine kinases, except for a localized induced fit in the activation loop.The co-crystal structure reveals the interactions between quizartinib and the active site of FLT3 that are key for achieving its high potency against both wild-type FLT3 as well as a FLT3 variant observed in many AML patients.This co-complex further provides a structural rationale for quizartinib-resistance mutations.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America; California Institute for Quantitative Biosciences, University of California, Berkeley, California, United States of America.

ABSTRACT
More than 30% of acute myeloid leukemia (AML) patients possess activating mutations in the receptor tyrosine kinase FMS-like tyrosine kinase 3 or FLT3. A small-molecule inhibitor of FLT3 (known as quizartinib or AC220) that is currently in clinical trials appears promising for the treatment of AML. Here, we report the co-crystal structure of the kinase domain of FLT3 in complex with quizartinib. FLT3 with quizartinib bound adopts an "Abl-like" inactive conformation with the activation loop stabilized in the "DFG-out" orientation and folded back onto the kinase domain. This conformation is similar to that observed for the uncomplexed intracellular domain of FLT3 as well as for related receptor tyrosine kinases, except for a localized induced fit in the activation loop. The co-crystal structure reveals the interactions between quizartinib and the active site of FLT3 that are key for achieving its high potency against both wild-type FLT3 as well as a FLT3 variant observed in many AML patients. This co-complex further provides a structural rationale for quizartinib-resistance mutations.

No MeSH data available.


Related in: MedlinePlus