p70S6K, or p70 S6 kinase, is a protein kinase that plays a crucial role in cell growth and metabolism. It is part of the mTOR signaling pathway, which regulates various cellular processes, including protein synthesis and cell proliferation. p70S6K is activated in response to nutrients, growth factors, and insulin, making it essential for cellular responses to these stimuli. This kinase specifically phosphorylates the ribosomal protein S6, which is involved in the translation of mRNA into proteins. By promoting protein synthesis, p70S6K contributes to muscle growth and development, making it a significant factor in both normal physiology and various diseases, including cancer and metabolic disorders.