| 背景 |
Protein Phosphatase 2A (PP2A) is an important and ubiquitously expressed serine threonine phosphatase and regulates the function by dephosphorylating many critical cellular molecules like Akt, p53, c-Myc and β-catenin. It plays a critical role in cellular processes, such as cell proliferation, signal transduction and apoptosis. Structurally, it is multifarious as it is composed of catalytic, scaffold and regulatory subunits. The regulatory subunit is the most diverse with temporal and spatial specificity. PP2A is structurally complex and exists in two different forms: dimeric form (PP2AD) and a trimeric form (PP2AT). The dimeric form is known as the core enzyme and is composed of the catalytic and scaffold subunit, while the trimeric form is an active holoenzyme complex which consists of three subunits: catalytic (PP2Ac), scaffold (PP2AA) and regulatory subunits (PP2AB). PP2A catalytic subunit (PP2Ac) is globular in structure, ubiquitously expressed in almost every tissue, and it is most abundant in the heart and brain. PP2Ac exists in two isoforms Cα and Cβ. The isoform Cα is predominantly expressed in the plasma membrane and Cβ in the cytoplasm and nucleus. Cα is expressed in higher abundance than Cβ due to its strong promoter activity as well as due to differences in the rate of mRNA turnover. |
