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Ribosomal S6 (S6K) belongs to the AGC family of Serine/Threonine protein kinases. There are two forms of S6K, alpha and beta, which have cytoplasmic and nuclear variants derived from alternative splicing (1). The activity of S6K is regulated by phosphorylation/ dephosphorylation events in cellular responses to various extracellular stimuli. Its activity has also been shown to be dependent on nutrient availability (3-6). The mechanism of activation of S6K is a multi-step process which is achieved by phosphorylating the 40S ribosomal protein S6, which then upregulates the translation of mRNA transcripts containing an oligopryimidine tract at the 5’ transcriptional start site (3-6). Recently, a highly homologous ribosomal S6 kinase, termed S6K2, was identified. It has 70% amino acid identity in the overall sequence with S6K1, and highly conserved potential phosphorylation sites of S6K1. However, the N- and C-terminal domains of S6K2 are quite different (2). As a result, S6K is a key player in the regulation of cell size, growth and glucose homeostasis.