Dynamic subcellular proteomics identifies novel regulators of adipocyte insulin action

Insulin acts on adipocytes to control whole-body glucose and lipid metabolism by inhibiting lipolysis and increasing glucose uptake. Regulation of these processes by insulin signalling is dependent on changes in protein localisation, for example GLUT4 delivery to the plasma membrane (PM). However, the extent of spatial proteomic changes in response to insulin signalling, and role these play in the cellular insulin response, is incomplete. Here, we use subcellular proteomics to map insulin-stimulated protein relocalisation in adipocytes on a cell-wide scale. Approximately 10% of proteins identified exhibited altered subcellular localisation in response to insulin. Since the PM was a major site of proteome remodelling in response to insulin, we performed additional PM proteome profiling to quantify insulin-responsive changes at the cell surface. These orthologous proteomics approaches revealed insulin-stimulated redistribution of the uncharacterised protein C3ORF18 to the PM. Studies in adipocytes depleted of C3ORF18 suggest this protein is required for maximal insulin signalling. Overall, our data provide an accessible resource of insulin-regulated changes in adipocyte protein localisation, and impetus for further work on how changes in protein localisation contribute to the cellular insulin response.