The Ser/Thr kinase AKT, also known as protein kinase B (PKB) has been the focus of tens of thousands of studies in diverse fields of biology and medicine. Activation of PI3K by extracellular stimuli results in activation of AKT in virtually all cells and tissues. The canonical pathway leading to AKT activation is initiated by the stimulation of receptor tyrosine kinases (RTK) or G protein coupled receptors (GPCR) leading to plasma membrane recruitment and activation of one or more isoforms of the class I PI3K family.Activation of PI3K results in the phosphorylation of two key residues on AKT1, T308 in the activation, or T-loop, of the catalytic protein kinase core, and S473 in a C-terminal hydrophobic motif. Phosphorylation of both residues is required for maximal activation of the kinase. 
Regulation also occurs on corresponding residues in AKT2 (T309 and S474) and AKT3 (T305 and S472). In addition to signal termination by lipid phosphatases such as PTEN and INPP4B, two critical protein phosphatases function to directly inactivate AKT. There have been many advances in our knowledge of the upstream regulatory inputs into AKT, key multifunctional downstream signaling nodes (GSK3, FoxO, mTORC1), which greatly expand the functional repertoire of Akt, and the complex circuitry of this dynamically branching and looping signaling network that is ubiquitous to nearly every cell in our body. Mouse and human genetic studies have also revealed physiological roles for the AKT network in nearly every organ system. The comprehension of AKT regulation and functions is particularly important given the consequences of AKT dysfunction in diverse pathological settings, including developmental and overgrowth syndromes, cancer, cardiovascular disease, insulin resistance and type-2 diabetes, inflammatory and autoimmune disorders, and neurological disorders. 


1.Manning BD, et al. Cell. 2017 Apr 20;169(3):381-405. doi: 10.1016/j.cell.2017.04.001.