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Engineered kinase activation reveals unique morphodynamic phenotypes and associated trafficking for Src family isoforms.

ABSTRACT: The Src kinase family comprises nine homologous members whose distinct expression patterns and cellular distributions indicate that they have unique roles. These roles have not been determined because genetic manipulation has not produced clearly distinct phenotypes, and the kinases' homology complicates generation of specific inhibitors. Through insertion of a modified FK506 binding protein (insertable FKBP12, iFKBP) into the protein kinase isoforms Fyn, Src, Lyn, and Yes, we engineered kinase analogs that can be activated within minutes in living cells (RapR analogs). Combining our RapR analogs with computational tools for quantifying and characterizing cellular dynamics, we demonstrate that Src family isoforms produce very different phenotypes, encompassing cell spreading, polarized motility, and production of long, thin cell extensions. Activation of Src and Fyn led to patterns of kinase translocation that correlated with morphological changes in temporally distinct stages. Phenotypes were dependent on N-terminal acylation, not on Src homology 3 (SH3) and Src homology 2 (SH2) domains, and correlated with movement between a perinuclear compartment, adhesions, and the plasma membrane.

SUBMITTER: Chu PH

PROVIDER: S-EPMC4151743 | biostudies-literature | 2014 Aug

REPOSITORIES: biostudies-literature

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Engineered kinase activation reveals unique morphodynamic phenotypes and associated trafficking for Src family isoforms.

Chu Pei-Hsuan PH Tsygankov Denis D Berginski Matthew E ME Dagliyan Onur O Gomez Shawn M SM Elston Timothy C TC Karginov Andrei V AV Hahn Klaus M KM

Proceedings of the National Academy of Sciences of the United States of America 20140812 34

The Src kinase family comprises nine homologous members whose distinct expression patterns and cellular distributions indicate that they have unique roles. These roles have not been determined because genetic manipulation has not produced clearly distinct phenotypes, and the kinases' homology complicates generation of specific inhibitors. Through insertion of a modified FK506 binding protein (insertable FKBP12, iFKBP) into the protein kinase isoforms Fyn, Src, Lyn, and Yes, we engineered kinase ...[more]

PMID: 25118278

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Project description:Protein kinases are enzymes that catalyze the covalent transfer of the γ-phosphate of an adenosine triphosphate (ATP) molecule onto a tyrosine, serine, threonine, or histidine residue in the substrate and thus send a chemical signal to networks of downstream proteins. They are important cellular signaling enzymes that regulate cell growth, proliferation, metabolism, differentiation, and migration. Unregulated protein kinase activity is often associated with a wide range of diseases, therefore making protein kinases major therapeutic targets. A prototypical system of central interest to understand the regulation of kinase activity is provided by tyrosine kinase c-Src, which belongs to the family of Src-related non-receptor tyrosine kinases (SFKs). Although the broad picture of autoinhibition via the regulatory domains and via the phosphorylation of the C-terminal tail is well characterized from a structural point of view, a detailed mechanistic understanding at the atomic-level is lacking. Advanced computational methods based on all-atom molecular dynamics (MD) simulations are employed to advance our understanding of tyrosine kinase activation. The computational studies suggest that the isolated kinase domain (KD) is energetically most favorable in the inactive conformation when the activation loop (A-loop) of the KD is not phosphorylated. The KD makes transient visits to a catalytically competent active-like conformation. The process of bimolecular trans-autophosphorylation of the A-loop eventually locks the KD in the active state. Activating point mutations may act by slightly increasing the population of the active-like conformation, enhancing the availability of the A-loop to be phosphorylated. The Src-homology 2 (SH2) and Src-homology 3 (SH3) regulatory domains, depending upon their configuration, either promote the inactive or the active state of the kinase domain. In addition to the roles played by the SH3, SH2, and KD, the Src-homology 4-Unique domain (SH4-U) region also serves as a key moderator of substrate specificity and kinase function. Thus, a fundamental understanding of the conformational propensity of the SH4-U region and how this affects the association to the membrane surface are likely to lead to the discovery of new intermediate states and alternate strategies for inhibition of kinase activity for drug discovery. The existence of a multitude of KD conformations poses a great challenge aimed at the design of specific inhibitors. One promising computational strategy to explore the conformational flexibility of the KD is to construct Markov state models from aggregated MD data.

Project description:Src family kinases are often overexpressed and constitutively active in cancer cells, where they represent promising targets for therapeutic intervention. In myeloid hematopoietic cells, Hck, Lyn, and Fgr are associated with both chronic and acute forms of myeloid leukemia. All three of these kinases are expressed in acute myeloid leukemia (AML), where high-level expression correlates with poor survival. The pyrrolopyrimidine Src-family kinase inhibitor A-419259 (also known as RK-20449) has been shown to significantly inhibit patient-derived AML bone marrow cell growth in immunocompromised mice. Recent work has identified an N-phenylbenzamide kinase inhibitor, known as TL02-59, which potently inhibited Fgr kinase activity in vitro and reversed orthotopic engraftment of AML cells in the bone marrow and spleen of immunocompromised mice following oral administration. The inhibitory mechanism of this compound with Fgr or other Src-family members has not been reported. Both wild-type Fgr and a tail mutant (i.e., replacement of Tyr527 with Phe) were shown to produce equal numbers of transformed colonies when expressed in rodent fibroblasts, whereas wild-type Hck transforming activity was completely repressed. In both Hck and Fgr, however, the tail tyrosine residue was shown to be phosphorylated, and hydrogen deuterium exchange mass spectrometry (HDX MS) of near-full-length Fgr was consistent with the closed conformation in solution, with the SH3 domain bound to the SH2-kinase linker and the tail bound to SH2. Here we present the first X-ray crystal structures of near-full-length Fgr bound to the ATP site inhibitors A-419259 and TL02-59. Structural changes induced by the inhibitors in the crystalline state were validated in solution using HDX MS, with A-419259 stabilizing the closed conformation and TL02-59 enhancing exposure of the SH3 domain to solvent. These new structures help to explain the constitutive activity of wild-type Fgr in cells as well as its unique sensitivity to TL02-59, which is currently in development for AML and other maladies.

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Engineered kinase activation reveals unique morphodynamic phenotypes and associated trafficking for Src family isoforms.

Publications

Engineered kinase activation reveals unique morphodynamic phenotypes and associated trafficking for Src family isoforms.

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