Regulation and function of ribosomal protein S6 kinase (S6K) within mTOR signalling networks

The ribosomal protein S6K (S6 kinase) represents an extensively studied effector of the TORC1 [TOR (target of rapamycin) complex 1], which possesses important yet incompletely defined roles in cellular and organismal physiology. TORC1 functions as an environmental sensor by integrating signals derived from diverse environmental cues to promote anabolic and inhibit catabolic cellular functions. mTORC1 (mammalian TORC1) phosphorylates and activates S6K1 and S6K2, whose first identified substrate was rpS6 (ribosomal protein S6), a component of the 40S ribosome. Studies over the past decade have uncovered a number of additional S6K1 substrates, revealing multiple levels at which the mTORC1-S6K1 axis regulates cell…