Updated project metadata. Various protein kinases are regulating the intracellular signaling network of skeletal muscle cells. Despite that many of the involved kinases are known, their downstream targets have remained largely unexplored. To deepen our understanding of the PI3K-AKT-mTOR-S6K and the RAF-MEK-ERK-RSK signaling network in myotubes, we globally analyzed changes in protein phosphorylation levels upon kinase inhibition within these pathways. The phosphoproteomics data were used to define potential targets of the kinases AKT, RSK and S6K, which share the substrate recognition motif RxRxxp[ST].