PO-188 Loss of uPAR function and suppression of malignant cell behaviour by a GPI-specific phospholipase C

Abstract

IntroductionThe urokinase receptor (uPAR) is a glycosylphosphatidylinositol (GPI)-anchored glycoprotein that promotes tissue remodelling and tumour progression. uPAR is highly expressed in many cancers and correlates with poor prognosis. uPAR mediates matrix degradation through protease recruitment and enhances tumour cell migration and signalling through vitronectin binding and interaction with integrins. Full-length uPAR is released from the cell surface, resulting in a soluble form (suPAR), but the mechanism and functional significance of uPAR shedding have been elusive.Material and methodsCell biological and biochemical assays; super-resolution microscopy; homology modelling; knockdown/knockout studies; xenograft model; patient survival analysis.Results and discussionsWe find that uPAR is released from the cell surface through GPI-anchor cleavage by a multi-pass membrane glycerophosphodiesterase, termed GDE3, acting as a GPI-specific phospholipase C (PLC), leading to loss of uPAR function. By contrast, GDE3’s closest relative GDE2 fails to cleave uPAR. By shedding uPAR from the cell surface, GDE3 abrogates uPAR-driven cell adhesion, spreading and lamellipodia formation on vitronectin. In breast cancer cells, high GDE3 expression depletes uPAR form distinct basolateral membrane microdomains resulting in a less transformed phenotype, as revealed by reduced matrix degradation, cell motility and colony formation. Furthermore, elevated GDE3 expression reduces tumour progression in a xenograft model and correlates with higher survival probability in breast cancer patients. Our results establish GDE3 as a cell-intrinsic GPI-specific PLC that sheds uPAR to attenuate malignant cell behaviour.ConclusionGDE3 is the first mammalian GPI-specific PLC that negatively regulates the uPAR signalling network, thereby suppressing the malignant phenotype of uPAR-positive cancer cells. Future studies should address how GDE3 activity and its substrate specificity are regulated.