Publication date: Available online 29 January 2019
Source: Journal of Allergy and Clinical Immunology
Author(s): Emilie Leroy, Thomas Balligand, Christian Pecquet, Céline Mouton, Didier Colau, Andrew K. Shiau, Alexandra Dusa, Stefan N. Constantinescu
Abstract
Background
Janus Kinase 2 (JAK2) plays pivotal roles in signaling by several cytokine receptors. The mutant JAK2 V617F is the most common molecular event associated with myeloproliferative neoplasms. Selective targeting of the mutant would be ideal for treating these pathologies by sparing essential JAK2 functions.
Objective
We characterize inhibitory strategies for JAK2 V617F and assess their impact on physiological signaling by distinct cytokine receptors.
Methods
Via structure-guided mutagenesis, we assessed the role of key residues around F617 and used a combination of cellular and biochemical assays to measure the activity of JAKs in reconstituted cells. We also assessed the effect of several specific JAK2 V617F inhibitory mutations on receptor dimerization using the NanoBiT protein complementation approach.
Results
We identified a novel JH2 αC mutation, A598F, suggested to inhibit the aromatic stacking between F617 with F594 and F595. Like other JAK2 V617F inhibitory mutations, A598F decreased oncogenic activation and spared cytokine activation, while preventing JAK2 V617F-promoted EpoR dimerization.
Surprisingly, A598F and other V617F inhibiting mutations (F595A, E596R, F537A) significantly impaired IFNγ signaling. This was specific for IFNγ since the inhibitory mutations preserved responses to ligand of a series of receptor complexes. Similarly, homologous mutations in JAK1 prevented signaling by IFNγ.
Conclusions
The region of the JH2 αC, which is required for JAK2 V617F hyperactivation, is crucial for relaying cytokine-induced signaling of the interferon gamma receptor. We discuss how strategies aiming to inhibit JAK2 V617F could be used for identifying inhibitors of IFNγ signaling.
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