Activation of phosphatidylinositol-3 kinase by nerve growth factor involves indirect coupling of the trk proto-oncogene with src homology 2 domains.
Growth factor receptor tyrosine kinases can form stable associations with intracellular proteins that contain src homology (SH) 2 domains, including the p85 regulatory subunit of phosphatidylinositol (PI)-3 kinase. The activation of this enzyme by growth factors is evaluated in PC12 pheochromocytoma cells and NIH 3T3 fibroblasts expressing the pp140c-trk nerve growth factor (NGF) receptor (3T3-c-trk). NGF causes the rapid stimulation of PI-3 kinase activity detected in anti-phosphotyrosine, but not in anti-trk, immunoprecipitates. This effect coincides with the tyrosine phosphorylation of two proteins, with molecular masses of of 100 kd and 110 kd, that coimmunoprecipitate with p85. Similar phosphorylation patterns are induced when an immobilized fusion protein containing the amino-terminal SH2 domain of p85 is used to precipitate tyrosine-phosphorylated proteins. Thus, although NGF produces the rapid activation of PI-3 kinase through a mechanism that involves tyrosine phosphorylation, there is no evidence for tyrosine phosphorylation of p85, or for its ligand-dependent association with the NGF receptor. Perhaps another phosphoprotein may link the NGF receptor to this enzyme.
Ohmichi
M
M
Department of Physiology, University of Michigan School of Medicine, Ann Arbor 48109.
Decker
S J
SJ
Saltiel
A R
AR
D016475:3T3 Cells; D000818:Animals; D004789:Enzyme Activation; D004815:Epidermal Growth Factor / Q000494:pharmacology; D016391:Genes, src; D015151:Immunoblotting; D007328:Insulin / Q000494:pharmacology; D007700:Kinetics; D046911:Macromolecular Substances; D051379:Mice; D009414:Nerve Growth Factors / Q000494:pharmacology*; D016716:PC12 Cells; D019869:Phosphatidylinositol 3-Kinases; D010770:Phosphotransferases / Q000378:metabolism*; D019000:Phosphotyrosine; D011505:Protein-Tyrosine Kinases / Q000235:genetics*; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D011519:Proto-Oncogenes / Q000187:drug effects; D020917:Receptor, trkA; D014443:Tyrosine / Q000031:analogs & derivatives / Q000032:analysis
D007328:Insulin; D046911:Macromolecular Substances; D009414:Nerve Growth Factors; D011518:Proto-Oncogene Proteins; D019000:Phosphotyrosine; D014443:Tyrosine; D004815:Epidermal Growth Factor; D010770:Phosphotransferases; D019869:Phosphatidylinositol 3-Kinases; D011505:Protein-Tyrosine Kinases; D020917:Receptor, trkA