JAK1 Pseudokinase V666G Mutant Dominantly Impairs JAK3 Phosphorylation and IL-2 Signaling

Overactive Janus kinases (JAKs) are known to drive leukemia, making them well-suited targets for treatment. We sought to identify new JAK-activating mutations and instead found a JAK1-inactivating pseudokinase mutation, V666G. In contrast to other pseudokinase mutations that canonically lead to an active kinase, the JAK1 V666G mutation led to under-activation seen by reduced phosphorylation. To understand the functional role of JAK1 V666G in modifying kinase activity we investigated its influence on other JAK kinases and within the Interleukin-2 pathway. JAK1 V666G not only inhibited its own activity, but its presence could inhibit other JAK kinases. These findings provide new insights into the potential of JAK1 pseudokinase to modulate its own activity, as well as of other JAK kinases. Thus, the features of the JAK1 V666 region in modifying JAK kinases can be exploited to allosterically inhibit overactive JAKs.

Automated summary

Overactive Janus kinases (JAKs) are potential targets for leukemia treatment. However, a JAK1-inactivating pseudokinase mutation, V666G, was discovered instead of new JAK-activating mutations. Unlike other pseudokinase mutations, the JAK1 V666G mutation led to under-activation. It not only inhibited its own activity but also other JAK kinases. These findings provide insights into the potential modulation of JAK kinases by the JAK1 pseudokinase and the opportunity to allosterically inhibit overactive JAKs.