Neuronal Functions of Protein Phosphatase 2A

Reversible protein phosphorylation is a common and important form of protein posttranslational modification which determines the proteins’ activities, substrate specificity and inhibitions or degradations, depending on the specific amino acid residue, or combination of residues, being targeted. While protein phosphorylations by kinases have been well studied, the importance of protein dephosphorylation by phosphatases has emerged over the past two decades in numerous cell functions, including cell cycle, development, regulation of signal transduction pathways, mitochondrial fussion and fission and disease states of cells. So far, there are five classes of phosphatases: tyrosine-specific phosphatases, serine/threonine specific phosphatases, dual specificity phosphatases, histidine phosphatase and lipid phosphatase. The subject of this review, Protein Phosphatase 2 (PP2, aka PP2A), is a member of the serine/threonine specific phosphatases which dephosphorylate a wide range of proteins including many of the phosphatases and kinases. In eukaryotic proteins, 86 and 12% are phosphorylated on Ser and Thr, respectively and the reversible phosphorylation of these proteins is key to their dynamic functions. The research done on PP2A has exploded in recent years and there are many excellent detail reviews each with a specific PP2A topic. This article presents a brief overview of PP2A functions in four aspects: Their substrate specificity, roles in Tau hyperphosphorylation, roles in mitochondria fusion and fission and nine examples of their roles in neuronal functions.