A novel pathway for the formation of phosphatidylinositol 3,4-bisphosphate. Phosphorylation of phosphatidylinositol 3-monophosphate by phosphatidylinositol-3-monophosphate 4-kinase.
Three polyphosphoinositides containing phosphate at the D-3 position of the inositol ring can be generated in vitro by phosphorylation of phosphatidylinositol, phosphatidylinositol 4-phosphate, and phosphatidylinositol 4,5-bisphosphate by a phosphatidylinositol-3-kinase (Auger, K. R., Serunian L. A., Soltoff, S. P., Libby, P., and Cantley, L. C. (1989) Cell 57, 167-175. An alternative pathway for in vivo synthesis of one of these lipids was recently suggested: phosphatidylinositol 3,4-bisphosphate could be produced by phosphorylation of phosphatidylinositol 3-phosphate at the D-4 position of the inositol ring (Yamamoto, K., and Lapetina, E. G. (1990) Biochem. Biophys. Res. Commun. 168, 466-472). Here we demonstrate the presence of an enzyme in human platelets that phosphorylates [32P]phosphatidylinositol 3-phosphate to produce [32P]phosphatidylinositol 3,4-bisphosphate. This enzyme is Mg2(+)-dependent and its apparent molecular mass is approximately 150 kDa as estimated by sucrose gradient centrifugation and gel filtration chromatography. Unlike the major phosphatidylinositol-4-kinase in platelets that is stimulated by the detergent Nonidet P-40, the phosphatidylinositol-3-phosphate-4-kinase is inhibited by Nonidet P-40. Both activities are also differentiated by the action of adenosine. The discovery of this new enzyme raises the possibility that multiple pathways exists for generating D-3 phosphorylated phosphoinositides.
Yamamoto
K
K
Division of Cell Biology, Burroughs Wellcome Co., Research Triangle Park, North Carolina 27709.
Graziani
A
A
Carpenter
C
C
Cantley
L C
LC
Lapetina
E G
EG
D019870:1-Phosphatidylinositol 4-Kinase; D000241:Adenosine / Q000494:pharmacology; D001792:Blood Platelets / Q000201:enzymology*; D002460:Cell Line; D002501:Centrifugation, Zonal; D002851:Chromatography, High Pressure Liquid; D003600:Cytosol / Q000201:enzymology; D006801:Humans; D007700:Kinetics; D004915:Leukemia, Erythroblastic, Acute; D019869:Phosphatidylinositol 3-Kinases; D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols / Q000096:biosynthesis* / Q000097:blood / Q000302:isolation & purification / Q000378:metabolism*; D010743:Phospholipids / Q000302:isolation & purification; D010761:Phosphorus Radioisotopes; D010766:Phosphorylation; D010770:Phosphotransferases / Q000097:blood / Q000302:isolation & purification / Q000378:metabolism*
D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols; D010743:Phospholipids; D010761:Phosphorus Radioisotopes; C055525:phosphatidylinositol 3-phosphate; D010770:Phosphotransferases; D019869:Phosphatidylinositol 3-Kinases; D019870:1-Phosphatidylinositol 4-Kinase; D000241:Adenosine