Phosphatidylinositol 3-phosphate (PI3P) is a

phospholipid Phospholipids are a class of lipids whose molecule has a hydrophilic "head" containing a phosphate group and two hydrophobic "tails" derived from fatty acids, joined by an alcohol residue (usually a glycerol molecule). Marine phospholipids typ ...

found in

cell membranes The cell membrane (also known as the plasma membrane or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of a cell from the outside environment (the extra ...

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 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 i ...

(PI 3-kinases) activity on

phosphatidylinositol 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 ...

. PtdIns3''P'' is dephosphorylated by the

myotubularin Myotubularin domain represents a region within eukaryotic myotubularin-related proteins that is sometimes found with the GRAM domain. Myotubularin is a dual-specific lipid phosphatase that dephosphorylates phosphatidylinositol 3-phosphate and ...

family of

phosphatase In biochemistry, a phosphatase is an enzyme that uses water to cleave a phosphoric acid Ester, monoester into a phosphate ion and an Alcohol (chemistry), alcohol. Because a phosphatase enzyme catalysis, catalyzes the hydrolysis of its Substrate ...

s, on the D3 position of the inositol ring, and can be converted to PtdIns(3,5)''P''₂ by the lipid kinase PIKfyve. Both FYVE domains and

PX domain The PX domain is a phosphoinositide-binding structural domain involved in targeting of proteins to cell membranes. This domain was first found in P40phox and p47phox domains of NADPH oxidase (phox stands for phagocytic oxidase). It was also iden ...

s – found in proteins such as

SNX1 Sorting nexin-1 is a protein that in humans is encoded by the SNX1 gene. The protein encoded by this gene is a sorting nexin. SNX1 is a component of the retromer complex. Function This gene encodes a member of the sorting nexin family. Mem ...

, HGS, and

EEA1 The gene EEA1 encodes for the 1400 amino acid protein, Early Endosome Antigen 1. EEA1 localizes exclusively to early endosomes and has an important role in endosomal trafficking. EEA1 binds directly to the phospholipid phosphatidylinositol 3-pho ...

– bind to PtdIns3''P''. The majority of PtdIns3''P'' appears to be constitutively synthesised by the

class III PI 3-kinase Class III PI 3-kinase is a subgroup of the enzyme family, phosphoinositide 3-kinase that share a common protein domain structure, substrate specificity and method of activation. There is only one known class III PI 3-kinase, Vps34, which is also th ...

PIK3C3 Phosphatidylinositol 3-kinase catalytic subunit type 3 is an enzyme subunit that in humans is encoded by the ''PIK3C3'' gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is ...

(Vps34), at endocytic membranes.

Class II PI 3-kinases Class II PI 3-kinases are a subgroup of the enzyme family, phosphoinositide 3-kinase that share a common protein domain structure, substrate specificity and method of activation. Class II PI 3-kinases were the most recently identified class of PI ...

also appear to synthesise PtdIns3''P'', their activity however appears to be regulated by a range of stimuli, including growth factors. This suggests that specific pools of PtdIns3''P'' may be synthesised upon cell stimulation.

References

Phospholipids {{Transferase-stub

See also

References