Phosphatidylinositol 3-phosphate
Encyclopedia
Phosphatidylinositol 3-phosphate (PtdIns3P or 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 (PI 3-kinases) activity on phosphatidylinositol
.
PtdIns3P is dephophosphorylated by the myotubularin
family of phosphatase
s, on the D3 position of the inositol ring, and can be converted to PtdIns(3,5)P2 by the lipid kinase PIKfyve.
Both FYVE domains and PX domain
s – found in proteins such as SNX1
, Hrs
, and EEA1
– bind to PtdIns3P.
The majority of PtdIns3P appears to be constitutively synthesised by the class III PI 3-kinase
, Vps34, at endocytic membranes. Class II PI 3-kinases
also appear to synthesise PtdIns3P, their activity however appears to be regulated by a range of stimuli, including growth factors. This suggests that specific pools of PtdIns3P may be synthesised upon cell stimulation.
Phospholipid
Phospholipids are a class of lipids that are a major component of all cell membranes as they can form lipid bilayers. Most phospholipids contain a diglyceride, a phosphate group, and a simple organic molecule such as choline; one exception to this rule is sphingomyelin, which is derived from...
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 (PI 3-kinases) activity on phosphatidylinositol
Phosphatidylinositol
Phosphatidylinositol is a negatively charged phospholipid and a minor component in the cytosolic side of eukaryotic cell membranes....
.
PtdIns3P is dephophosphorylated by the myotubularin
Myotubularin
Myotubularin domain represents a region within eukaryotic myotubularin-related proteins that is sometimes found with . Myotubularin is a dual-specific lipid phosphatase that dephosphorylates phosphatidylinositol 3-phosphate and phosphatidylinositol -bi-phosphate...
family of phosphatase
Phosphatase
A phosphatase is an enzyme that removes a phosphate group from its substrate by hydrolysing phosphoric acid monoesters into a phosphate ion and a molecule with a free hydroxyl group . This action is directly opposite to that of phosphorylases and kinases, which attach phosphate groups to their...
s, on the D3 position of the inositol ring, and can be converted to PtdIns(3,5)P2 by the lipid kinase PIKfyve.
Both FYVE domains and PX domain
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...
s – found in proteins such as SNX1
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 :...
, Hrs
HRS
HRS may refer to:*Florida Department of Health and Rehabilitative Services*Head-Royce School*Health and Retirement Study*Heart Rhythm Society*Helena Romanes School and Sixth Form Centre*Hepatorenal syndrome...
, and EEA1
EEA1
EEA1 is Early Endosome Antigen 1 protein that binds phospholipid vesicles containing phosphatidylinositol 3-phosphate, which is necessary for endosomal trafficking. It binds lipids through its FYVE domain and forms a homodimer through a coiled coil domain....
– bind to PtdIns3P.
The majority of PtdIns3P appears to be constitutively synthesised by the class III PI 3-kinase
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....
, Vps34, at endocytic membranes. Class II PI 3-kinases
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....
also appear to synthesise PtdIns3P, their activity however appears to be regulated by a range of stimuli, including growth factors. This suggests that specific pools of PtdIns3P may be synthesised upon cell stimulation.