Growth factor signalling via TSC2 phosphorylation reduces the inhibitory function of TSC1/TSC2 towards Rheb, which results in activation of Rheb and finally of mTORC1 [53???57]. mTORC1 has to be regarded as a key node in cell signalling, because it integrates many intra- and extracellular signals such as growth factors (insulin, IGF-1), energy-sensing signals (glucose, AMP/ATP ratio regulating AMP