Akt is a subfamily of serine/threonine kinases (Protein Kinase B) that includes AKT1, AKT2, and AKT3. Akt resides in the cytosol in an inactive conformation, until the cell is stimulated leading to the activation of PI3K. Activation of PI3K converts plasma membrane phospholipids PIP2 to PIP3, leading to the recruitment of Akt to the membrane. Akt is then activated by phosphorylation by PDK1 and multiple catalytic proteins. To a lesser extent, Akt activation can occur trough other tyrosine or serine/threonine kinases, in response to heat shock or following an increase in calcium concentration. Once active, Akt translocates to the cytosol and nucleus, where it regulates (inhibitory or stimulatory) a wide range of proteins involved in critical cellular processes.