Akt kinase, which is also known as Protein Kinase B (PKB), is one of the key members of extended serine/threonine protein kinase family. This kinase plays a crucial role in multiple cellular processes such as glucose metabolism, cell proliferation, apoptosis, transcription and cell migration.
Three main Akt isoforms (Akt1, Akt2, and Akt3) have been identified in human cells. The first member is deeply involved in cellular survival pathways by inhibiting apoptotic processes. It is also able to induce protein synthesis pathways, and is therefore a key signaling protein in the cellular pathways that lead to skeletal muscle hypertrophy, and general tissue growth. Since it can block apoptosis, and thereby promote cell survival, Akt1 has been implicated as a major factor in many types of cancer. Akt1 was originally identified as the oncogene in the transforming retrovirus AKT8. The second isoform, Akt2, is an important signaling molecule in the Insulin signaling pathway. It is required to induce glucose transport. The role of Akt3 is less clear, though it appears to be predominantly expressed in brain. Akt is associated with tumor cell survival, proliferation, and invasiveness. The activation of Akt is also one of the most frequent alterations observed in human cancer and tumor cells. Tumor cells that have constantly active Akt may depend on Akt for survival.