Disease-related mutations in PI3Kγ disrupt regulatory C-terminal dynamics and reveal a path to selective inhibitors

Class I Phosphoinositide 3-kinases (PI3Ks) are master regulators of cellular functions, with the class IB PI3K catalytic subunit (p110 gamma) playing key roles in immune signalling. p110 gamma is a key factor in inflammatory diseases and has been identified as a therapeutic target for cancers due to its immunomodulatory role. Using a combined biochemical/biophysical approach, we have revealed insight into regulation of kinase activity, specifically defining how immunodeficiency and oncogenic mutations of R1021 in the C-terminus can inactivate or activate enzyme activity. Screening of inhibitors using HDX-MS revealed that activation loop-binding inhibitors induce allosteric conformational changes that mimic those in the R1021C mutant. Structural analysis of advanced PI3K inhibitors in clinical development revealed novel binding pockets that can be exploited for further therapeutic development. Overall, this work provides unique insights into regulatory mechanisms that control PI3K gamma kinase activity and shows a framework for the design of PI3K isoform and mutant selective inhibitors.

Automated summary

Class I Phosphoinositide 3-kinases (PI3Ks) play crucial roles in cellular functions, with the catalytic subunit p110 gamma being important in immune signaling and diseases like cancer. This study provides insights into the regulation of p110 gamma kinase activity and potential therapeutic targets for inhibitor development through structural analysis and screening. The findings also reveal the impact of immunodeficiency and oncogenic mutations on enzyme activity, with implications for future drug discovery efforts targeting PI3K isoforms.