Phosphorylation of phosphatase-1alpha in cells expressing v-src
Villa-Moruzzi, E.; Puntoni, F.
Biochemical and Biophysical Research Communications 219(3): 863-867
1996
ISSN/ISBN: 0006-291X PMID: 8645271 Document Number: 464474
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: PP1-alpha, PP1-gamma-1 and PP1-delta. In A4 cells the three PP1 isoforms were all phosphorylated on Ser, but only PP1-alpha 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 the Tyr-phosphorylated PP1-alpha 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 PP1-alpha was inactivated. Altogether the data suggest that PP1-alpha might be a target of v-src "in vivo."