Proteomic characterization of GSK3 beta knockout shows altered cell adhesion and metabolic pathway utilisation in colorectal cancer cells

Glycogen-specific kinase (GSK3 beta) is an integral regulator of the Wnt signalling pathway as well as many other diverse signalling pathways and processes. Dys-regulation of GSK3 beta is implicated in many different pathologies, including neurodegenerative disorders as well as many different tumour types. In the context of tumour development, GSK3 beta has been shown to play both oncogenic and tumour suppressor roles, depending upon tissue, signalling environment or disease progression. Although multiple substrates of the GSK3 beta kinase have been identified, the wider protein networks within which GSK3 beta participates are not well known, and the consequences of these interactions not well understood. In this study, LC-MS/MS expression analysis was performed using knockout GSK3 beta colorectal cancer cells and isogenic controls in colorectal cancer cell lines carrying dominant stabilizing mutations of beta-catenin. Consistent with the role of GSK3 beta, we found that beta-catenin levels and canonical Wnt activity are unaffected by knockout of GSK3 beta and therefore used this knockout cell model to identify other processes in which GSK3 beta is implicated. Quantitative proteomic analysis revealed perturbation of proteins involved in cell-cell adhesion, and we characterized the phenotype and altered proteomic profiles associated with this. We also characterized the perturbation of metabolic pathways resulting from GSK3 beta knockout and identified defects in glycogen metabolism. In summary, using a precision colorectal cancer cell-line knockout model with constitutively activated beta-catenin we identified several of the diverse pathways and processes associated with GSK3 beta function.