Phosphatidylinositol 3-phosphate explained

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 (PI 3-kinases) activity on phosphatidylinositol.^[1]

PtdIns3P is dephosphorylated by the myotubularin family of phosphatases, on the D3 position of the inositol ring, and can be converted to PtdIns(3,5)P₂ by the lipid kinase PIKfyve.^[2]

Both FYVE domains and PX domains  - found in proteins such as SNX1, HGS, and EEA1  - bind to PtdIns3P.^[3]

The majority of PtdIns3P appears to be constitutively synthesised by the class III PI 3-kinase, PIK3C3 (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.

See also

• Phosphatidylinositol 3-phosphate-binding protein 2

Notes and References

1. Gillooly DJ, Simonsen A, Stenmark H . Cellular functions of phosphatidylinositol 3-phosphate and FYVE domain proteins . The Biochemical Journal . 355 . Pt 2 . 249–58 . April 2001 . 11284710 . 1221734 . 10.1042/0264-6021:3550249 .
2. De Craene JO, Bertazzi DL, Bär S, Friant S . Phosphoinositides, Major Actors in Membrane Trafficking and Lipid Signaling Pathways . International Journal of Molecular Sciences . 18 . 3 . 634 . March 2017 . 28294977 . 5372647 . 10.3390/ijms18030634 . free .
3. Stenmark H, Aasland R, Driscoll PC . The phosphatidylinositol 3-phosphate-binding FYVE finger . FEBS Letters . 513 . 1 . 77–84 . February 2002 . 11911884 . 10.1016/s0014-5793(01)03308-7 . 2002FEBSL.513...77S .