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Phosphatidylinositol or inositol phospholipid is a biomolecule. It was initially called "inosite" when it was discovered by Léon Maquenne and Johann Joseph von Scherer in the late 19th century. It was discovered in bacteria but later also found in eukaryotes, and was found to be a signaling molecule.
The mammalian target of rapamycin (mTOR), also referred to as the mechanistic target of rapamycin, and sometimes called FK506-binding protein 12-rapamycin-associated protein 1 (FRAP1), is a kinase that in humans is encoded by the MTOR gene. mTOR is a member of the phosphatidylinositol 3-kinase-related kinase family of protein kinases.
Phosphoinositide phospholipase C is a family of eukaryotic intracellular enzymes that play an important role in signal transduction processes. These enzymes belong to a larger superfamily of Phospholipase C. Other families of phospholipase C enzymes have been identified in bacteria and trypanosomes. Phospholipases C are phosphodiesterases.
Phosphatidylinositol (3,4,5)-trisphosphate (PtdIns(3,4,5)P3), abbreviated PIP3, is the product of the class I phosphoinositide 3-kinases' (PI 3-kinases) phosphorylation of phosphatidylinositol (4,5)-bisphosphate (PIP2). It is a phospholipid that resides on the plasma membrane.
Phosphoinositide 3-kinases (PI3Ks), also called phosphatidylinositol 3-kinases, are a family of enzymes involved in cellular functions such as cell growth, proliferation, differentiation, motility, survival and intracellular trafficking, which in turn are involved in cancer.
Phosphatidylinositol 4,5-bisphosphate or PtdIns(4,5)P2, also known simply as PIP2 or PI(4,5)P2, is a minor phospholipid component of cell membranes. PtdIns(4,5)P2 is enriched at the plasma membrane where it is a substrate for a number of important signaling proteins. PIP2 also forms lipid clusters that sort proteins.
Phosphatidylinositol 3-phosphate (PI3P) is a phospholipid found in cell membranes that helps to recruit a range of proteins, many of which are involved in protein trafficking, to the membranes. It is the product of both the class II and III phosphoinositide 3-kinases activity on phosphatidylinositol.
Phosphatidylinositol (3,4)-bisphosphate is a minor phospholipid component of cell membranes, yet an important second messenger. The generation of PtdIns(3,4)P2 at the plasma membrane activates a number of important cell signaling pathways.
Phosphatidylinositol 3,5-bisphosphate is one of the seven phosphoinositides found in eukaryotic cell membranes. In quiescent cells, the PtdIns(3,5)P2 levels, typically quantified by HPLC, are the lowest amongst the constitutively present phosphoinositides. They are approximately 3 to 5-fold lower as compared to PtdIns3P and PtdIns5P levels, and more than 100-fold lower than the abundant PtdIns4P and PtdIns(4,5)P2. PtdIns(3,5)P2 was first reported to occur in mouse fibroblasts and budding yeast S. cerevisiae in 1997. In S. cerevisiae PtdIns(3,5)P2 levels increase dramatically during hyperosmotic shock. The response to hyperosmotic challenge is not conserved in most tested mammalian cells except for differentiated 3T3L1 adipocytes.
In molecular biology the FYVE zinc finger domain is named after the four cysteine-rich proteins: Fab 1, YOTB, Vac 1, and EEA1, in which it has been found. FYVE domains bind phosphatidylinositol 3-phosphate, in a way dependent on its metal ion coordination and basic amino acids. The FYVE domain inserts into cell membranes in a pH-dependent manner. The FYVE domain has been connected to vacuolar protein sorting and endosome function.
Ribosomal protein S6 kinase beta-1 (S6K1), also known as p70S6 kinase, is an enzyme that in humans is encoded by the RPS6KB1 gene. It is a serine/threonine kinase that acts downstream of PIP3 and phosphoinositide-dependent kinase-1 in the PI3 kinase pathway. As the name suggests, its target substrate is the S6 ribosomal protein. Phosphorylation of S6 induces protein synthesis at the ribosome.
Phosphatidylinositol 3-kinase catalytic subunit type 3 is an enzyme subunit that in humans is encoded by the PIK3C3 gene. It's a class III phosphoinositide 3-kinase.
PIKfyve, a FYVE finger-containing phosphoinositide kinase, is an enzyme that in humans is encoded by the PIKFYVE gene.
ULK1 is an enzyme that in humans is encoded by the ULK1 gene.
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 and Akt.
Phosphatidylinositol 5-phosphate (PtdIns5P) is a phosphoinositide, one of the phosphorylated derivatives of phosphatidylinositol (PtdIns), that are well-established membrane-anchored regulatory molecules. Phosphoinositides participate in signaling events that control cytoskeletal dynamics, intracellular membrane trafficking, cell proliferation and many other cellular functions. Generally, phosphoinositides transduce signals by recruiting specific phosphoinositide-binding proteins to intracellular membranes.
Lewis C. Cantley is an American cell biologist and biochemist who has made significant advances to the understanding of cancer metabolism. Among his most notable contributions are the discovery and study of the enzyme PI-3-kinase, now known to be important to understanding cancer and diabetes mellitus. He is currently Meyer Director and Professor of Cancer Biology at the Sandra and Edward Meyer Cancer Center at Weill Cornell Medicine in New York City. He was formerly a professor in the Departments of Systems Biology and Medicine at Harvard Medical School, and the Director of Cancer Research at the Beth Israel Deaconess Medical Center, in Boston, Massachusetts. In 2016, he was elected Chairman of the Board for the Hope Funds for Cancer Research.
Phosphoinositide 3-kinase regulatory subunit 4, also known as PI3-kinase regulatory subunit 4 or PI3-kinase p150 subunit or phosphoinositide 3-kinase adaptor protein, or VPS15 is an enzyme that in humans is encoded by the PIK3R4 gene.
Polyphosphoinositide phosphatase also known as phosphatidylinositol 3,5-bisphosphate 5-phosphatase or SAC domain-containing protein 3 (Sac3) is an enzyme that in humans is encoded by the FIG4 gene. Fig4 is an abbreviation for Factor-Induced Gene.
Protein VAC14 homolog, also known as ArPIKfyve, is a protein that in humans is encoded by the VAC14 gene.
References
- ↑ Backer, J.M. (2008). "The regulation and function of Class III PI3Ks: novel roles for Vps34". Biochem. J. 410 (1): 1–17. doi:10.1042/bj20071427. PMID 18215151.
