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Phosphorylation of c-Abl by protein kinase Pak2 regulates differential binding of ABI2 and CRK
Jin-Hun Jung1, Ann Marie Pendergast, Patricia A Zipfel
1Department of Biochemistry, University of California, Riverside, California 92521, USA.
Abstract:
The tyrosine kinase c-Abl is implicated in a variety of cellular processes that are tightly regulated by c-Abl kinase activity and/or by interactions between c-Abl and other signaling molecules. The interaction of c-Abl with the Abl interactor protein Abi2 is shown to be negatively regulated by phosphorylation of serines 637 and 638. These serines are adjacent to the PxxP motif (PTPPKRS637S638SFR) that binds the SH3 domain of Abi. Phosphorylation of the Abl 593-730 fragment by Pak2 dramatically reduces Abi2 binding ( approximately 90%). Mutation of serines 637-639 to alanine (3A) or aspartate (3D) results in an increased tyrosine kinase activity of c-Abl 3D, and a slight reduction of the activity of the 3A mutant, as compared to wild-type (WT) c-Abl. The interaction between Abi2 and c-Abl 3D is inhibited by 80%, as compared to WT c-Abl or c-Abl 3A. This is accompanied by a 2-fold increase in binding of Crk to c-Abl 3D. The data indicate a molecular mechanism whereby phosphorylation of c-Abl by Pak2 inhibits the interaction between the SH3 domain of Abi2 and the PxxP motif of c-Abl. This phosphorylation enhances the association of c-Abl with the substrate Crk and increases c-Abl-mediated phosphorylation of Crk, thus altering the association of Crk with other signaling molecules.
Insights
Phosphorylation of tyrosine kinase c-Abl by Pak2 regulates its interaction with Abi2. This process enhances c-Abl
Area of Science:
- Cellular signaling
- Protein phosphorylation
- Tyrosine kinase regulation
Background:
- c-Abl tyrosine kinase activity is crucial for cellular processes.
- c-Abl interacts with various signaling molecules, including Abl interactor protein Abi2.
- The interaction between c-Abl and Abi2 is regulated by phosphorylation.
Purpose of the Study:
- To elucidate the molecular mechanism of c-Abl and Abi2 interaction regulation.
- To investigate the role of Pak2 phosphorylation in modulating c-Abl activity and substrate binding.
Main Methods:
- Site-directed mutagenesis of c-Abl serine residues (S637-639) to alanine (3A) or aspartate (3D).
- Analysis of Abi2 binding to wild-type (WT) c-Abl, c-Abl 3A, and c-Abl 3D mutants.
- Assessment of c-Abl kinase activity and Crk binding to different c-Abl variants.
Main Results:
- Pak2 phosphorylation of c-Abl dramatically reduces Abi2 binding.
- Mutations mimicking phosphorylation (3D) significantly inhibit Abi2 interaction and enhance Crk binding.
- c-Abl 3D exhibits increased tyrosine kinase activity compared to WT and 3A mutants.
Conclusions:
- Pak2-mediated phosphorylation of c-Abl inhibits Abi2 binding by disrupting SH3 domain interaction.
- This phosphorylation enhances c-Abl association with Crk, increasing Crk phosphorylation.
- The findings reveal a mechanism altering Crk interactions within signaling pathways.
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