The Cbl family of proteins are multidomain proteins that have a dual function, as protein adaptors for tyrosine kinase receptors and as E3-ubiquitin conjugating enzymes. As such, they perform a variety of functions in different tissues and in response to various stimuli. In adipocytes, c-Cbl functions as an insulin receptor adaptor protein together with CAP (Cbl Associated Protein) and APS to regulate the insulin-stimulated translocation of the glucose transporter Glut4 to the plasma membrane. We have shown that in muscle, c-Cbl is also rapidly phosphorylated in tyrosine residues in response to insulin administration, however, this does not lead to the activation of the same signalling cascades that regulate glucose transport in adipocytes. To elucidate the function of Cbl and CAP in muscle cells we have constitutively knocked-down the expression of c-Cbl or CAP in C2C12 cells using lentiviral transduction of specific shRNAs and carried out gene expression profiling experiments to identify genes that are regulated by these proteins. Quantitative PCR and biochemical analyses were carried out to validate the DNA microarray data. We found that Cbl depleted cells display normal insulin-stimulated activation of phosphatidylinositol 3-kinase/Akt, and Mitogen Activated Kinases (p44/p42) in response to insulin. However, Cbl KD cells exhibit basal increased activation of AMPK- regulated kinase compared to non-infected control cells or cells expressing Non-targeting shRNAs. Microarray data analysis revealed that genes coding for proteins involved in lipid metabolism were altered in Cbl and CAP KD cell lines compared to control cells. Validation experiments confirmed reduced transcript levels for long chain fatty acid acylCoA synthases and carnitine palmitoyltransferase genes, suggesting reduced fatty acid activation and transport into the mitochondria. In vitro assays using palmitate as substrate showed that fatty acid acyl CoA synthase activity was reduced in Cbl and CAP KD cells. Cbl-deficient cells also displayed higher triglyceride levels than control cells. These data suggest that Cbl signalling contributes to regulate lipid metabolism and fatty acid utilization in muscle cells.