Phosphorylation of phosphatase-1alpha in cells expressing v-src.
Phosphatase-1 (PP1) is phosphorylated "in vitro" by the tyrosine-kinases c-src, v-src and v-abl. In the case of src, this induces enzyme inactivation. We investigated whether in NIH-3T3 cells expressing v-src (A4 cells) PP1 was phosphorylated on Tyr and inactivated. In mammalian cells, three PP1 isoforms are present: PP1alpha, PP1gamma1 and PP1delta. In A4 cells the three PP1 isoforms were all phosphorylated on Ser, but only PP1alpha was also phosphorylated on Tyr. A lower level of PP1 phosphorylation, and on Ser only, was found also in wild-type NIH-3T3 cells. In A4 cells most of Tyr-phosphorylated PP1alpha was cytosolic. Also the PP1 activity was decreased in the cytosol of the A4 cells. Assay of the three immunoprecipitated PP1 isoforms indicated that only PP1alpha was inactivated. Altogether the data suggest that PP1alpha might be a target of v-src "in vivo".
Villa-Moruzzi
E
E
Department of Biomedicine, University of Pisa, Italy. villa@biomed.unipi.it
Puntoni
F
F
D016475:3T3 Cells; D000818:Animals; D001345:Autoradiography; D003600:Cytosol / Q000201:enzymology; D016391:Genes, src; D051379:Mice; D015688:Oncogene Protein pp60(v-src) / Q000096:biosynthesis / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000302:isolation & purification / Q000378:metabolism*; D010750:Phosphoproteins / Q000302:isolation & purification / Q000378:metabolism; D010761:Phosphorus Radioisotopes; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000032:analysis; D054645:Protein Phosphatase 1; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*
D010710:Phosphates; D010750:Phosphoproteins; D010761:Phosphorus Radioisotopes; D019000:Phosphotyrosine; D011505:Protein-Tyrosine Kinases; D015688:Oncogene Protein pp60(v-src); D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1