Ribosomal protein S6 kinase 1 (RPS6K1) is the best characterized effector of the mammalian Target of Rapamycin (TOR), an evolutionarily conserved serine/threonine kinase that regulates cell growth and cell cycle through its ability to integrate signals from nutrient levels and growth factors. Nutrients and growth factors stimulate a complex including TOR, raptor (regulatory associated protein of TOR), and GbetaL to phosphorylate RPS6K1 and the eukaryotic initiation factor 4E binding protein (4EBP1), leading to increased protein synthesis and cell growth. RPS6K1 is thought to desensitize tissues to insulin as mice deficient in RPS6K1 have been shown to be hypersensitive to insulin and impervious to obesity-induced insulin resistance seen in wild type obese mice.