Mitogen-mediated protein phosphorylation in Werner's syndrome fibroblasts.
DNA synthesis of WF-1 fibroblasts derived from a patient with Werner's syndrome was stimulated by fetal calf serum and adult human serum but not by various mitogens including epidermal growth factor, platelet-derived growth factor (PDGF), fibroblast growth factor, insulin and 12-O-tetradecanoylphorbol-13-acetate (TPA). To clarify the cause of nonresponsiveness to these mitogens, we compared the rate of protein phosphorylation in normal fibroblasts HF-O and Werner's WF-1 cells. PDGF and TPA enhanced the phosphorylation of a Mr 80 K protein, which is known to be a substrate for protein kinase C, both in HF-O and WF-1 cells. This indicates that the pathway involving PDGF receptor, phosphatidylinositol turnover and protein kinase C activation is operational in WF-1 cells. Several species of phosphoproteins of Mr 250 K, 135 K, 110 K, 78 K and 42 K were detected in normal HF-O cells by immunoprecipitation using an anti-phosphotyrosine antibody. The same species of phosphoproteins were detected in Werner's WF-1 cells at passage 6, but only when treated with various mitogens and were not detected in WF-1 cells at passage 10 even after the PDGF- or TPA-treatment. These results suggest that the reduction of phosphorylation of these target proteins may be in part responsible for the diminished mitogenic responsiveness of Werner's fibroblasts.
Hirai
M
M
Department of Molecular Biology, Keio University School of Medicine, Tokyo, Japan.
Amagai
M
M
Tajima
S
S
Nishikawa
T
T
Shimizu
N
N
D000328:Adult; D002455:Cell Division / Q000187:drug effects; D004247:DNA / Q000096:biosynthesis; D005347:Fibroblasts / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D008297:Male; D008934:Mitogens / Q000502:physiology*; D010750:Phosphoproteins / Q000032:analysis; D010766:Phosphorylation; D019000:Phosphotyrosine; D011506:Proteins / Q000032:analysis / Q000378:metabolism*; D014443:Tyrosine / Q000031:analogs & derivatives / Q000032:analysis; D014898:Werner Syndrome / Q000378:metabolism* / Q000473:pathology
D008934:Mitogens; D010750:Phosphoproteins; D011506:Proteins; D019000:Phosphotyrosine; D014443:Tyrosine; D004247:DNA