The LCLAT1/LYCAT acyltransferase is required for EGF-mediated phosphatidylinositol-3,4,5-trisphosphate and Akt signalling

Receptor tyrosine kinases such as epidermal growth factor receptor (EGFR) stimulate phosphoinositide 3-kinases (PI3Ks) to convert phosphatidylinositol-4,5-bisphosophate [PtdIns(4,5)P2] into phosphatidylinositol-3,4,5-trisphosphate [PtdIns(3,4,5)P3]. PtdIns(3,4,5)P3 then remodels actin and gene expression patterns, and boosts cell survival and proliferation. PtdIns(3,4,5)P3 partly achieves these functions by stimulating the kinase Akt, which phosphorylates targets like Tsc2 and GSK3β. Consequently, unchecked upregulation of PtdIns(3,4,5)P3-Akt signalling promotes tumourgenesis. Interestingly, 50-70% of PtdIns and PtdInsPs have stearate and arachidonate at sn -1 and sn -2 positions of glycerol, respectively, forming a species known as 38:4-PtdIns/PtdInsPs. LCLAT1 and MBOAT7 acyltransferases are respectively responsible for enriching PtdIns in this acyl format. We previously showed that disruption of LCLAT1 lowered PtdIns(4,5)P2 levels and perturbed endocytosis and endocytic trafficking. However, the role of LCLAT1 in receptor tyrosine kinase and PtdIns(3,4,5)P3 signaling was not explored. Here, we show that LCLAT1 silencing in MDA-MB-231 and ARPE-19 cells abated the levels of PtdIns(3,4,5)P3 in response to EGF signalling. Importantly, LCLAT1-silenced cells were also impaired for EGF-driven Akt activation and downstream signalling, and consequently, were depressed for cell proliferation and survival. Thus, our work provides first evidence that the LCLAT1 acyltransferase is required for receptor tyrosine kinase signalling and may represent a novel target for therapeutic development against cancers. ### Competing Interest Statement The authors have declared no competing interest. * BSA : bovine serum albumin EGF : epidermal growth factor EGFR : epidermal growth factor receptor IP3 : inositol-1,4,5-trisphosphate ER : endoplasmic reticulum PtdIns : phosphatidylinositol PtdIns(3)P : phosphatidylinositol-3-phosphate PtdIns(4,5)P2 : phosphatidylinositol-4,5-bisphosphate PtdIns(3,4,5)P3 : phosphatidylinositol-3,4,5-trisphosphate PtdInsP : phosphoinositide TIRF : total internal reflection fluorescence TNBC : triple negative breast cancer