Enhanced SH3/Linker Interaction Overcomes Abl Kinase Activation by Gatekeeper and Myristic Acid Binding Pocket Mutations and Increases Sensitivity to Small Molecule Inhibitors*

Thomas E Smithgall,Thomas E Wales,Shoghag Panjarian,Shugui Chen,Roxana E Iacob,John R Engen

doi:10.1074/jbc.m112.431312

Thomas E Smithgall, Thomas E Wales + Show 4 more

Open Access

https://doi.org/10.1074/jbc.m112.431312

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Abstract

Multidomain kinases such as c-Src and c-Abl are regulated by complex allosteric interactions involving their noncatalytic SH3 and SH2 domains. Here we show that enhancing natural allosteric control of kinase activity by SH3/linker engagement has long-range suppressive effects on the kinase activity of the c-Abl core. Surprisingly, enhanced SH3/linker interaction also dramatically sensitized the Bcr-Abl tyrosine kinase associated with chronic myelogenous leukemia to small molecule inhibitors that target either the active site or the myristic acid binding pocket in the kinase domain C-lobe. Dynamics analyses using hydrogen exchange mass spectrometry revealed a remarkable allosteric network linking the SH3 domain, the myristic acid binding pocket, and the active site of the c-Abl core, providing a structural basis for the biological observations. These results suggest a rational strategy for enhanced drug targeting of Bcr-Abl and other multidomain kinase systems that use multiple small molecules to exploit natural mechanisms of kinase control.

Highlights

Abl kinases are regulated by noncatalytic domains that allosterically impact kinase domain structure and inhibitor sensitivity
Enhanced SH3/linker interaction dramatically sensitized the Bcr-Abl tyrosine kinase associated with chronic myelogenous leukemia to small molecule inhibitors that target either the active site or the myristic acid binding pocket in the kinase domain C-lobe
HAL9 reversed the Abl core T315I activation loop of tyrosine phosphorylation (Tyr(P)412) by more than 60%, whereas phosphorylation of the SH3 domain (Tyr(P)89) was almost completely suppressed. Consistent with these observations, HAL9 substitution substantially reduced the cellular phosphotyrosine content. These results show that the destabilizing impact of the Abl gatekeeper mutation on the Abl kinase domain remains under the allosteric control of the SH3/linker interaction

Summary

Introduction

Abl kinases are regulated by noncatalytic domains that allosterically impact kinase domain structure and inhibitor sensitivity. Significance: Stabilizers of SH3/linker interaction may sensitize Bcr-Abl to kinase domain inhibitors, providing a new route to allosteric kinase control Multidomain kinases such as c-Src and c-Abl are regulated by complex allosteric interactions involving their noncatalytic SH3 and SH2 domains. Dynamics analyses using hydrogen exchange mass spectrometry revealed a remarkable allosteric network linking the SH3 domain, the myristic acid binding pocket, and the active site of the c-Abl core, providing a structural basis for the biological observations. These results suggest a rational strategy for enhanced drug targeting of Bcr-Abl and other multidomain kinase systems that use multiple small molecules to exploit natural mechanisms of kinase control

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