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Daple-FLT3 (CCDC88C-FLT3) gene fusion requires the coiled-coil domain for maximal activation and pericentrosomal
Abstract:
Gene fusions are stable protein products often occurring from chromosomal rearrangements. These chimeric proteins typically contain distinct molecular entities from each parent gene, and thus, create a product with altered or aberrant function. Gene fusions are frequently found in cancers, including Leukemia. Here, we characterize the kinase activity and subcellular distribution of the Daple-FLT3 (CCDC88C-FLT3) fusion oncoprotein-a rare, but recurrent gene fusion found in patients with hematological malignancies. The protein contains the FLT3 kinase domain and is activated without ligand stimulation. This leads to activation in STAT5a, AKT, and MAPK signaling, which can be modulated by the tyrosine kinase inhibitor (TKIs) sorafenib, and to a lesser degree, imatinib. Moreover, fusion of this kinase domain to Daple facilitates its localization to the pericentrosomal space and enhances kinase activation. These findings provide evidence that targeting Daple-FLT3 outside of its kinase domain may be a complementary approach with TKI therapy.
Key Points:
Daple-FLT3 fusion proteins contain a constitutively active kinase domain, activating distinct signaling molecules in cellsCoiled-coil domain on Daple is dispensable for kinase activation, but necessary for maximal activation.
Insights
We characterized the Daple-FLT3 fusion oncoprotein, a driver of hematological malignancies. Targeting this fusion protein, particularly outside its kinase domain, may complement tyrosine kinase inhibitor therapy.
Area of Science:
- Oncology
- Molecular Biology
- Biochemistry
Background:
- Gene fusions, resulting from chromosomal rearrangements, create chimeric proteins with altered functions.
- These fusion proteins are frequently implicated in cancer development, including leukemia.
- The Daple-FLT3 (CCDC88C-FLT3) fusion oncoprotein is a rare but recurrent finding in hematological malignancies.
Purpose of the Study:
- To characterize the kinase activity and subcellular localization of the Daple-FLT3 fusion oncoprotein.
- To investigate the signaling pathways activated by Daple-FLT3.
- To evaluate the efficacy of tyrosine kinase inhibitors (TKIs) against Daple-FLT3.
Main Methods:
- Biochemical assays to determine kinase activity.
- Cellular localization studies using microscopy.
- Pharmacological inhibition using TKIs like sorafenib and imatinib.
Main Results:
- The Daple-FLT3 fusion protein possesses a constitutively active FLT3 kinase domain, independent of ligand stimulation.
- It activates downstream signaling pathways including STAT5a, AKT, and MAPK.
- Fusion to Daple enhances kinase activation and directs the oncoprotein to the pericentrosomal space.
- Sorafenib effectively modulated Daple-FLT3 activity, while imatinib showed a lesser effect.
Conclusions:
- Daple-FLT3 is a constitutively active oncoprotein driving key signaling pathways in hematological malignancies.
- Targeting Daple-FLT3, potentially through its Daple moiety, could be a novel therapeutic strategy.
- Combined therapeutic approaches, including TKIs and novel agents targeting the fusion protein, may offer improved treatment outcomes.
