Insulin-like growth factor-1 induces tyrosyl phosphorylation of nuclear proteins.
Stimulation of mesangial cells with insulin-like growth factor-1 (IGF-1) resulted in the rapid tyrosyl phosphorylation of nuclear proteins as indicated by fluorescence microscopy of cells stained with anti-phosphotyrosine antibodies. Immunoprecipitation of nuclear extracts with anti-phosphotyrosine antibodies revealed that IGF-1 induced a transient increase in immunoreactive phosphotyrosine in nuclear proteins of 43, 95, and 160 kDa. Using a double immunoprecipitation protocol, the transcription factor c-Jun was also found to increase in immunoreactive phosphotyrosine in response to IGF-1. A similar pattern of tyrosyl phosphorylation of nuclear proteins was observed in the epidermoid carcinoma cell line CaSki. These data suggest that tyrosyl phosphorylation of nuclear proteins may be a step in the transduction of mitogenic signals.
Oemar
B S
BS
Department of Ophthalmology and Visual Science, Yale University School of Medicine, New Haven, Connecticut 06510.
Law
N M
NM
Rosenzweig
S A
SA
D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D004591:Electrophoresis, Polyacrylamide Gel; D005920:Glomerular Mesangium / Q000166:cytology / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008856:Microscopy, Fluorescence; D009687:Nuclear Proteins / Q000378:metabolism*; D010766:Phosphorylation; D011233:Precipitin Tests; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism; D017451:Receptors, Somatomedin; D015398:Signal Transduction; D014443:Tyrosine / Q000378:metabolism*
D009687:Nuclear Proteins; D016755:Proto-Oncogene Proteins c-jun; D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; D014443:Tyrosine; D007334:Insulin-Like Growth Factor I