The programmes of work in the laboratory are currently aimed at understanding the molecular mechanisms and physiological significance of intracellular signalling networks which involve a family of enzymes called phosphoinositide 3OH-kinases (PI3Ks).
PI3Ks are now accepted to be critical regulators of numerous important and complex cell responses, including cell growth, division, survival and movement.
PI3Ks catalyse the formation of one or more critical phospholipid messenger molecules, which signal information by binding to specific domains in target proteins. Currently the best understood pathway involves the activation of Class I PI3Ks by cell surface receptors.
In recent years, the laboratory has increasingly focused on the role of PI3Ks in the signalling mechanisms which allow receptors on neutrophils (white blood cells) to control various aspects of neutrophil function.
Neutrophils are key players in the front line of our immune system, responsible primarily for the recognition and destruction of bacterial and fungal pathogens. However, they are also involved in the amplification cascades that underlie various inflammatory pathologies, e.g. Acute Respiratory Distress Syndrome (ARDS) and rheumatoid arthritis.
Although the regulation of branching morphogenesis by spatially distributed cues is well established, the underlying intracellular signaling mechanisms are not well understood. The development of the lacrimal gland is driven by fibroblast growth factor (FGF) signaling, which activates phospholipase C gamma (PLCγ). Here, we showed that mutating the PLCγ1 binding site on Fgfr2 leads to ectopic branching and hyperplasia in the lacrimal gland, which was phenocopied by either deleting PLCγ1 or disabling any of its SH2 domains. PLCγ1 inactivation did not change the level of Fgfr2 or affect mitogen-activated protein kinase (MAPK) signaling but instead led to sustained AKT phosphorylation due to increased phosphatidylinositol 3,4,5-trisphosphate (PIP3) production. Consistent with this, the PLCγ1 mutant phenotype can be reproduced by the elevation of phosphatidylinositol 3-kinase (PI3K) signaling in Pten knockout and attenuated by blocking AKT signaling. Our findings demonstrate that FGF-activated PLCγ modulates PI3K signaling by shifting phosphoinositide metabolism, revealing the crucial role of PLCγ in branching morphogenesis and organ size control.
Metastatic uveal melanoma is an aggressive disease with limited effective therapeutic options. To comprehensively map monogenic and digenic dependencies, we performed CRISPR-Cas9 screening in ten extensively profiled human uveal melanoma cell line models. Analysis involved genome-wide single-gene and combinatorial paired-gene CRISPR libraries. Among our 76 uveal melanoma-specific essential genes and 105 synthetic lethal gene pairs, we identified and validated the CDP-diacylglycerol synthase 2 gene (CDS2) as a genetic dependency in the context of low CDP-diacylglycerol synthase 1 gene (CDS1) expression. We further demonstrate that CDS1/CDS2 forms a synthetic lethal interaction in vivo and reveal that CDS2 knockout results in the disruption of phosphoinositide synthesis and increased cellular apoptosis and that re-expression of CDS1 rescues this cell fitness defect. We extend our analysis using pan-cancer data, confirming increased CDS2 essentiality in diverse tumor types with low CDS1 expression. Thus, the CDS1/CDS2 axis is a therapeutic target across a range of cancers.
Insulin and other growth factors are key regulators of liver gene expression, including in metabolic diseases. Most of the phosphoinositide 3-kinase (PI3K) activity induced by insulin is considered to be dependent on PI3Kα. We used mice lacking p110α, the catalytic subunit of PI3Kα, to investigate its role in the regulation of liver gene expression in health and in metabolic dysfunction-associated steatotic liver disease (MASLD). The absence of hepatocyte PI3Kα reduced maximal insulin-induced PI3K activity and signaling, promoted glucose intolerance in lean mice and significantly regulated liver gene expression, including insulin-sensitive genes, in ad libitum feeding. Some of the defective regulation of gene expression in response to hepatocyte-restricted insulin receptor deletion was related to PI3Kα signaling. In addition, though PI3Kα deletion in hepatocytes promoted insulin resistance, it was protective against steatotic liver disease in diet-induced obesity. In the absence of hepatocyte PI3Kα, the effect of diet-induced obesity on liver gene expression was significantly altered, with changes in rhythmic gene expression in liver. Altogether, this study highlights the specific role of p110α in the control of liver gene expression in physiology and in the metabolic rewiring that occurs during MASLD.