UC San Diego

G proteins and G protein-coupled receptors activate a diverse array of signal transduction pathways that promote cell growth and survival. Indeed, hot spot-activating mutations in GNAQ/GNA11, encoding Gαq proteins, are known to be driver oncogenes in uveal melanoma (UM), for which there are limited effective therapies currently available. Focal adhesion kinase (FAK) has been recently shown to be a central mediator of Gαq-driven signaling in UM, and as a result, is being explored clinically as a therapeutic target for UM, both alone and in combination therapies. Despite this, the repertoire of Gαq/FAK-regulated signaling mechanisms have not been fully elucidated. Here, we used a whole-genome CRISPR screen in GNAQ-mutant UM cells to identify mechanisms that, when overactivated, lead to reduced sensitivity to FAK inhibition. In this way, we found that the PI3K/AKT signaling pathway represented a major resistance driver. Our dissection of the underlying mechanisms revealed that Gαq promotes PI3K/AKT activation via a conserved signaling circuitry mediated by FAK. Further analysis demonstrated that FAK activates PI3K through the association and tyrosine phosphorylation of the p85 regulatory subunit of PI3K and that UM cells require PI3K/AKT signaling for survival. These findings establish a novel link between Gαq-driven signaling and the stimulation of PI3K as well as demonstrate aberrant activation of signaling networks underlying the growth and survival of UM and other Gαq-driven malignancies.