BACR 13: The Warburg effect: Regulation of integrin endocytosis and function
1University of Southampton, Southampton, UK
Tumour-cells metabolise via ATP-inefficient aerobic glycolysis, undergoing the Warburg effect. Glycolysis improves nutrient incorporation into the biomass for enhanced cell proliferation and leads to an increase in the ratio of the reduced form of the glycolytic coenzyme nicotinamide adenine dinucleotide (NADH) to its oxidised form (NAD+), resulting in activation of glycolytic sensors; C-terminal binding proteins. According to our results CtBPs regulate integrin-dependent cell motility in various cancer types, thus the Warburg effect produces more invasive tumour-cells. 90% of cancer-related deaths result from tumour metastasis, dependent on altered interactions between cell adhesion receptors integrins and the extracellular matrix (ECM). Integrins play a major role in the regulation of cell motility thus, investigating the mechanism regulating integrin activation and trafficking is important. Our data proposes a link between metabolism and clathrin-dependent integrin endocytosis as the protein Eps15, vital for clathrin-mediated endocytosis, is down-regulated upon CtBP1 knockdown in cancer cells.
We examine the link between tumour-cell metabolism and integrin-dependent functions in a range of tumour cell-lines treated with small interfering siRNAs against CtBPs and Eps15 to downregulate endogenous expression. Integrin-receptor endocytosis is examined using a functional endocytosis assay and integrin-dependent function is measured in vitro using a range of functional assays including adhesion, cell spreading, Transwell® migration, Matrigel® invasion and organotypic models.
Eps15 expression is dependent on CtBP expression, both at the transcriptional and translational level. Loss of Eps15 significantly reduces tumour cell motility, suppressing migration and invasion, and reduces the efficiency of integrin endocytosis and speed of tumour cell adhesion.
The metabolic sensor CtBP1 and the endocytosis regulator Eps15 are involved in cancer cell migration and invasion and future work will aim to determine whether this pathway is a mechanism whereby the Warburg effect may promote tumour cell movement by promoting integrin recycling.