Gene expressions and activities of protein phosphatases PP1 and PP2A in rat liver regeneration after partial hepatectomy

Role of PP2A in intracellular signal transduction pathways

“…In contrast, analyzing the amount of mRNA, others have demonstrated increased PP2A mRNA levels during the early stages of G1 in mammalian cells (129,130). Moreover, Kakinoki et al (131), by performing partial hepatectomy, presented evidence of almost constant levels of PP2A protein in regenerating liver, despite a 30-fold increase in PP2A mRNA. These observed discrepancies between elevated mRNA levels and rather constant protein levels can now be explained by the finding of a potent autoregulatory mechanism of PP2A synthesis that appears to work at the level of translation (125).…”

PP2Acα positively regulates the termination of liver regeneration in mice through the AKT/GSK3β/Cyclin D1 pathway

“…In 1975, Ballal found that the incorporation of 32 P by proteins increased by 20-fold 48 hrs post-PH, indicating that protein phosphorylation is important for LR[26]. However, Kakinoki analyzed the gene expression and activity of protein phosphatases in regenerating livers in rat and found that PP2A mRNA levels had two peaks, at 6 and 10-12 h, but its activity remained constant[27]. PP2A consists of three subunits: A, B and C. The A and B subunits exert regulatory functions, and C is the catalytic subunit.…”

Induction of protein phosphatase type 2A in response to disruption of cell-matrix interactions

“…The elevated expression and activity of PP2A is even more impressive and remarkable in light of earlier observations that failed to detect increased levels of PP2A protein under various growth conditions. For example, in different mammalian cells and in fission yeast, it has been shown that the level of PP2A protein remains strikingly constant throughout the cell cycle (Kinoshita et al, 1990;Ruediger et al, 1991;Virshup et al, 1989), and this has also been observed in regenerating liver after hepatectomy (Kakinoki et al, 1992). The constant amounts of PP2A protein are likely due to the presence of an autoregulatory mechanism that appears to function at the level of translational regulation (Baharians and Schönthal, 1998).…”