The biogenesis of active protein phosphatase 2A holoenzymes: a tightly regulated process creating phosphatase specificity

• Published in: The FEBS journal 2013-01, Vol.280 (2), p.644-661
• Main Authors: Sents, Ward, Ivanova, Elitsa, Lambrecht, Caroline, Haesen, Dorien, Janssens, Veerle
• Format: Article
• Language: English
• Subjects: Adaptor Proteins, Signal Transducing; Carboxylic Ester Hydrolases - metabolism; carboxymethylation; Holoenzymes - biosynthesis; Holoenzymes - metabolism; Humans; Intracellular Signaling Peptides and Proteins - metabolism; leucine carboxyl methyl transferase 1 (LCMT1); Models, Biological; Molecular Chaperones; peptidyl‐prolyl cis/trans isomerase; phosphatase 2A phosphatase activator (PTPA); Phosphoprotein Phosphatases - metabolism; Protein O-Methyltransferase - metabolism; Protein Phosphatase 2 - biosynthesis; Protein Phosphatase 2 - metabolism; protein phosphatase type 2A (PP2A); protein phosphatase type 2A methyl esterase 1 (PME‐1); protein phosphatase type 4 (PP4); protein phosphatase type 6 (PP6); Substrate Specificity; target of rapamycin signaling pathway regulator‐like 1 (TIPRL1)
• ISSN: 1742-464X; 1742-4658
• DOI: 10.1111/j.1742-4658.2012.08579.x

Protein phosphatase type 2A (PP2A) enzymes constitute a large family of Ser/Thr phosphatases with multiple functions in cellular signaling and physiology. The composition of heterotrimeric PP2A holoenzymes, resulting from the combinatorial assembly of a catalytic C subunit, a structural A subunit, and regulatory B‐type subunit, provides the essential determinants for substrate specificity, subcellular targeting, and fine‐tuning of phosphatase activity, largely explaining why PP2A is functionally involved in so many diverse physiological processes, sometimes in seemingly opposing ways. In this review, we highlight how PP2A holoenzyme biogenesis and enzymatic activity are controlled by a sophisticatedly coordinated network of five PP2A modulators, consisting of α4, phosphatase 2A phosphatase activator (PTPA), leucine carboxyl methyl transferase 1 (LCMT1), PP2A methyl esterase 1 (PME‐1) and, potentially, target of rapamycin signaling pathway regulator‐like 1 (TIPRL1), which serve to prevent promiscuous phosphatase activity until the holoenzyme is completely assembled. Likewise, these modulators may come into play when PP2A holoenzymes are disassembled following particular cellular stresses. Malfunctioning of these cellular control mechanisms contributes to human disease. The potential therapeutic benefits or pitfalls of interfering with these regulatory mechanisms will be briefly discussed. Protein phosphatase 2A (PP2A) specificity is largely determined by the particular subunit composition of the holoenzyme. The biogenesis of these holoenzymes is a complicated process, tightly controlled by a sophisticatedly coordinated network of five PP2A modulators, consisting of α4, PTPA, LCMT1, PME‐1 and potentially TIPRL1. Although less clear, the biogenesis of the PP2A‐like phosphatases PP4 and PP6 may prove to be highly similar.