PDGF-dependent tyrosine phosphorylation stimulates production of novel polyphosphoinositides in intact cells.
A phosphatidylinositol (PI) kinase activity associated with certain protein tyrosine kinases important in cell proliferation phosphorylates the 3' hydroxyl position of PI to produce phosphatidylinositol-3-phosphate (PI-3-P). Here we report that, in addition to PI-3' kinase activity, anti-phosphotyrosine (alpha-P-tyr) immunoprecipitates from platelet-derived growth factor (PDGF)-stimulated smooth muscle cells (SMC) contain lipid kinase activities that utilize the substrates phosphatidylinositol-4-phosphate (PI-4-P) and phosphatidylinositol-4,5-bisphosphate (PI-4,5-P2). These activities are absent in alpha-P-tyr immunoprecipitates from quiescent SMC. The product of PI-4-P phosphorylation appears to be phosphatidylinositol-3,4-bisphosphate (PI-3,4-P2), a lipid not previously reported. The product of PI-4,5-P2 phosphorylation is phosphatidylinositol-trisphosphate (PIP3). PI-3-P was detected in quiescent SMC and increased only slightly in response to PDGF. PIP3 and the putative PI-3,4-P2 appeared only after the addition of mitogen. Both the temporal production of these novel phospholipids after PDGF stimulation and the observation of the enzymatic activities that produce them in alpha-P-tyr immunoprecipitates suggest that these phospholipids are excellent candidates for mediators of the PDGF mitogenic response.
Auger
K R
KR
Department of Cellular and Molecular Physiology, Tufts University School of Medicine, Boston, Massachusetts 02111.
Serunian
L A
LA
Soltoff
S P
SP
Libby
P
P
Cantley
L C
LC
D019870:1-Phosphatidylinositol 4-Kinase; D002118:Calcium / Q000494:pharmacology; D005786:Gene Expression Regulation; D006801:Humans; D007295:Inositol Phosphates / Q000032:analysis; D008938:Mitosis / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology; D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols / Q000032:analysis / Q000378:metabolism* / Q000502:physiology; D010766:Phosphorylation; D010770:Phosphotransferases / Q000378:metabolism; D019000:Phosphotyrosine; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology* / Q000502:physiology; D011233:Precipitin Tests; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism; D017479:Receptors, Platelet-Derived Growth Factor; D014443:Tyrosine / Q000031:analogs & derivatives / Q000276:immunology
D007295:Inositol Phosphates; D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols; D010982:Platelet-Derived Growth Factor; D011956:Receptors, Cell Surface; D019000:Phosphotyrosine; D014443:Tyrosine; D010770:Phosphotransferases; D019870:1-Phosphatidylinositol 4-Kinase; D011505:Protein-Tyrosine Kinases; D017479:Receptors, Platelet-Derived Growth Factor; D002118:Calcium