p70S6

p70S6, also known as ribosomal protein S6 kinase beta-1 or RPS6KB1, is a serine/threonine kinase that plays a crucial role in cellular growth, proliferation, and survival. It is a key downstream effector of the mammalian target of rapamycin (mTOR) signaling pathway. Activation of p70S6 occurs through a series of phosphorylation events, primarily initiated by mTOR complex 1 (mTORC1). Once activated, p70S6 phosphorylates the S6 ribosomal protein (rpS6) on multiple serine residues. This phosphorylation event is thought to enhance the translation of specific mRNAs, particularly those encoding ribosomal proteins and translation factors, leading to increased protein synthesis and cell growth.

Beyond rpS6, p70S6 can also phosphorylate other substrates, including eukaryotic initiation factor 4B (eIF4B) and PDCD4, further contributing to its role in regulating translation and cell cycle progression. Dysregulation of p70S6 activity has been implicated in various diseases, including cancer, where it can promote tumor growth and resistance to therapy. Conversely, its role in normal cellular processes makes it a target for therapeutic interventions aimed at controlling cell growth.