2022 RCMI | C51213 - Elisa Robles

ABSTRACT #C51213 - JAK1 ALL-MUTATION DOMINANTLY IMPAIRS TYR PHOSPHORYLATION

AUTHORS :: E ROBLES-ESCAJEDA; AH Grant; G Rodriguez; AC Rodriguez; A Lazarski; JE Mohl; M-Y Leung; RA Kirken

AFFILIATIONS :: Border Biomedical Research Center, University of Texas at El Paso (ER-E, AHG, GR, ACR, AL, JEM, M-YL, RAK)

PURPOSE: Overactive Janus kinases (JAKs) are known to drive leukemias making them well suited targets for treatment. We sought to identify new JAK activating mutations and instead found a JAK1 inactivating pseudokinase mutation. In contrast to other pseudokinase mutations that canonically lead to an active kinase, the JAK1 V666 mutation led to under activation seen by reduced phosphorylation. To understand the functional role of JAK1 V666 in modifying kinase activity we investigated its influence on other JAK kinases and within the Interleukin-2 (IL-2) pathway. METHODS: Using Whole Exome Sequencing, the unreported mutation V666, was detected within the pseudokinase JH2 domain of JAK1 from a Hispanic Acute Lymphoblastic Leukemia (ALL) patient from the UTEP Biorepository and OncoMiner cancer database. A combination of site-directed mutagenesis, in vitro kinase assays, and structural analysis were used in the study to delineate the impact of JAK1 V666 on IL-2 signal transduction. RESULTS: Here we observed a dominant negative effect of inactive JAK1 on JAK3. Specifically, inactive forms of JAK1 produced an inhibitory effect on autoactivation of the JAK family. Interestingly, in the absence of JAK1, JAK3 was capable of tyrosine autophosphorylation. Yet the presence of JAK1 V666 could attenuate JAK3 autophosphorylation and IL-2 induced transphosphorylation. JAK1 V666 not only inhibited its own activity but its presence could inhibit other JAK kinases. DISCUSSION/CONCLUSION: These findings provide new insights into the JAK1 pseudokinase in its potential to modulate not only its own activity but of other JAK kinases as well. Thus, the features of the JAK1 Val 666 region in modifying JAK kinases can be exploited to inhibit overactive JAKs.

GRANT SUPPORT :: GRANT SUPPORT: This work was supported by grants from the National Institute on Minority Health and Health Disparities, a component of the National Institutes of Health (5U54MD007592) and from the RISE Scholars Program at UTEP funded by the National Institute of General Medical Sciences (R25GM069621-18).