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bioRxiv · 10.1101/2023.05.04.539492

Molecular basis for Gβγ-mediated activation ofphosphoinositide 3-kinase γ

Chen, C.-l.·Syahirah, R.·Ravala, S.·Yen, Y.-C.·Klose, T.·Deng, Q.·Tesmer, J. J. G.
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Abstract

The conversion of PIP2 to PIP3 by phosphoinositide 3-kinase {gamma} (PI3K{gamma}) is a critical step in neutrophil chemotaxis and is essential for metastasis in many types of cancer. PI3K{gamma} is activated via directed interaction with G{beta}{gamma} heterodimers released from cell-surface G protein-coupled receptors (GPCRs) responding to extracellular signals. To resolve how G{beta}{gamma} activates PI3K{gamma}, we determined cryo-EM reconstructions of PI3K{gamma}-G{beta}{gamma} complexes in the presence of various substrates/analogs, revealing two distinct G{beta}{gamma} binding sites, one on the p110{gamma} helical domain and one on the C-terminal domain of the p101 subunit. Comparison of these complexes with structures of PI3K{gamma} alone demonstrates conformational changes in the kinase domain upon G{beta}{gamma} binding similar to those induced by Ras{middle dot}GTP. Assays of variants perturbing the two G{beta}{gamma} binding sites and interdomain contacts that change upon G{beta}{gamma} binding suggest that G{beta}{gamma} not only recruits the enzyme to membranes but also allosterically controls activity via both sites. Studies in a zebrafish model examining neutrophil migration are consistent with these results. These findings set the stage for future detailed investigation of G{beta}{gamma}-mediated activation mechanisms in this enzyme family and will aid in developing drugs selective for PI3K{gamma}.

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Chen, C.-l., Syahirah, R., Ravala, S., Yen, Y.-C., Klose, T., Deng, Q., Tesmer, J. J. G.. 2023-05-05. Molecular basis for Gβγ-mediated activation ofphosphoinositide 3-kinase γ. https://doi.org/10.1101/2023.05.04.539492

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