Ribosomal protein S6 (rpS6 or eS6) is a component of the 40S ribosomal subunit and is therefore involved in translation. Mouse model studies have shown that phosphorylation of eS6 is involved in the regulation of cell size, cell proliferation, and glucose homeostasis [PMID: 16166381, PMID: 16679021, PMID: 19479038]. p70S6K is a serine/threonine kinase that phosphorylates the S6 protein of the 40S ribosomal subunit (phosphorylated S6 ribosomal protein (phospho-S6rp)) at several sites, including serines 235 and 236, leading to initiation of protein synthesis [PMID: 16860938].