Akt/PKB signaling pathway

rdf:langString Akt/PKB signaling pathway

rdf:langString The Akt signaling pathway or PI3K-Akt signaling pathway is a signal transduction pathway that promotes survival and growth in response to extracellular signals. Key proteins involved are PI3K (phosphatidylinositol 3-kinase) and Akt (protein kinase B). Initial stimulation by one of the growth factors causes activation of a cell surface receptor and phosphorylation of PI3K. Activated PI3K then phosphorylates lipids on the plasma membrane, forming second messenger phosphatidylinositol (3,4,5)-trisphosphate (PIP3). Akt, a serine/threonine kinase, is recruited to the membrane by interaction with these phosphoinositide docking sites, so that it can be fully activated.Activated Akt mediates downstream responses, including cell survival, growth, proliferation, cell migration and angiogenesis, by phosphorylating a range of intracellular proteins. The pathway is present in all cells of higher eukaryotes and is highly conserved. The pathway is highly regulated by multiple mechanisms, often involving cross-talk with other signaling pathways. Problems with PI3K-Akt pathway regulation can lead to an increase in signaling activity. This has been linked to a range of diseases such as cancer and type 2 diabetes. A major antagonist of PI3K activity is PTEN (phosphatase and tensin homolog), a tumour suppressor which is often mutated or lost in cancer cells. Akt phosphorylates as many as 100 different substrates, leading to a wide range of effects on cells.