Neoplastic alterations in subcellular distribution of type 1α protein phosphatase in rat ascites hepatoma cells

Neoplastic alterations of type 1α protein phosphatase (PP1α) have been studied in rat ascites hepatoma cells, using regenerating liver after partial hepatectomy and normal rat liver as controls. In the particulate fraction of hepatomas, potential PP1 activity and the amount of PP1α were remarkably increased compared with either regenerating or normal livers. In the nuclear fraction, PP1 activity and the amount of PP1α were increased in hepatoma compared with the controls. The nuclear PP1 activity in hepatomas was activated by treatment with CO2+/trypsin, whereas that of normal or regenerating liver was not activated. These characteristic alterations of PP1α in its amount and subcellular distribution may be implicated in malignant phenotype(s) such as uncontrolled cell growth.