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Effects of JAK2 V556F mutation on the JAK2's activity, structural stability and the transformation of Ba/F3 cells
Qing-Yun Wu1, Meng-Meng Ma2, Yu-Xue Tong2
1Blood Diseases Institute, Xuzhou Medical University, Xuzhou, Jiangsu, China; Department of Hematology, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, China.
Abstract:
Although roles of somatic JAK2 mutations in clonally myeloproliferative neoplasms (MPNs) are well established, roles of germline JAK2 mutations in the pathogenesis of MPNs remain unclear. Recently, a novel activating, germline JAK2 F556V mutation was identified and involved in the pathogenesis of MPNs, but, its pathogenesis mechanism was still unknown. In this study, homology models of JAK2 demonstrated that F556 located between two threonine residues which interacted with ATP phosphate groups by hydrogen bonds, Thr555 with the γ-phosphate and Thr557 with the β-phosphate in the active site of JAK2's JH2 domain. Moreover, the hydrogen bond between Thr557 and Arg715 played vital roles in sustaining the structural conformation of JH2's active site and JH1-JH2 domains' interactions. When F556 was replaced by other amino acids except Trp, the hydrogen bond, JH2 domain's structural conformation and JH1-JH2 domains' interactions disrupted for changing the helix between β2 and β3 strands which finally caused JAK2 activation. Mechanistic and functional studies showed that JAK2 F556V mutation disrupted JAK2 JH2 domain's activity, caused JAK2-STAT5 pathway activation and promoted the proliferation of BaF3 cells. Thus, our results herein may provide clues to understand the pathogenesis mechanism of JAK2 F556V mutation in the MPNs.
Insights
Germline JAK2 F556V mutations disrupt the JAK2 JH2 domain, activating the JAK2-STAT5 pathway and promoting cell proliferation, offering insights into myeloproliferative neoplasms (MPNs) pathogenesis.
Area of Science:
- Molecular Biology
- Genetics
- Hematology
Background:
- Somatic JAK2 mutations are linked to myeloproliferative neoplasms (MPNs).
- The role of germline JAK2 mutations in MPN pathogenesis is not well understood.
- A novel germline JAK2 F556V mutation has been implicated in MPNs, but its mechanism remains unclear.
Purpose of the Study:
- To elucidate the pathogenic mechanism of the germline JAK2 F556V mutation in MPNs.
- To investigate how this mutation affects JAK2 structure and function.
- To understand the downstream signaling consequences of the JAK2 F556V mutation.
Main Methods:
- Homology modeling of the JAK2 protein structure.
- Analysis of hydrogen bonding interactions in the JAK2 JH2 domain.
- Site-directed mutagenesis to replace F556 with other amino acids.
- Mechanistic and functional studies using cell-based assays (e.g., BaF3 cells).
Main Results:
- The F556 residue is critical for maintaining the structural integrity of the JAK2 JH2 active site and JH1-JH2 domain interactions via hydrogen bonds.
- Mutation of F556 disrupts these hydrogen bonds, alters the protein's helical structure, and leads to JAK2 activation.
- The JAK2 F556V mutation impairs JH2 domain activity, activates the JAK2-STAT5 signaling pathway, and enhances BaF3 cell proliferation.
Conclusions:
- The JAK2 F556V mutation disrupts normal JAK2 structure and function, leading to aberrant signaling.
- This provides a mechanistic explanation for the involvement of germline JAK2 F556V mutations in MPN pathogenesis.
- Understanding this mechanism may offer therapeutic targets for MPNs.