JAK2 V617F Dimerizes Homodimeric Cytokine Receptors Cytosolic Domains By Requiring Pseudokinase Domain Residues That Promote JAK2 Dimerization and Oncogenic Activity

JAK2 plays roles in several signaling pathways by binding to multiple distinct cytokine receptors. Dysfunction of JAK2 signaling is associated with hematopoietic malignancies. The acquired mutation JAK2 V617F, which constitutively activates JAK2 kinase, is the most common molecular event associated with myeloproliferative disorders.Using a combination of bioluminescence energy transfer and protein fragment complementation assays we show that V617F located in the pseudokinase domain of JAK2 plays an important role on JAK2 dimerization via the C-terminal kinase domains. Using NanoBRET we show that JAK2 dimerization via the C-terminal domains is reduced by single mutations (E596R 1, F595A 2, A598F and F537A) that in the context of JAK2 V617F revert the mutant to wild type phenotype with respect to signaling by homodimeric erythropoietin and thrombopoietin receptors (EpoR and TpoR). Thus, residues that are required for V617F activation strengthen JAK2 dimerization via C-terminal kinase domains, implicating the pseudokinase domain in global JAK2 dimerization and suggesting that part of the V617F activation mechanism relies on dimerization of mutated pseudokinase domains.Using NanoBiT protein fragment complementation assay, we explored the effects of JAK2 V617F on dimerization of the cytosolic ends of cytokine receptors. We show that JAK2 V617F promotes strong enhancement of dimerization of EpoR and TpoR cytosolic domains, when compared to wild type JAK2. This result is unexpected ...

Source: Blood - November 21, 2018 Category: Hematology Authors: Leroy, E., Balligand, T., Constantinescu, S. N. Tags: 635. Myeloproliferative Syndromes: Basic Science: Identification of Novel Therapeutic Targets Source Type: research