scholarly journals The split protein phosphatase system

2018 ◽  
Vol 475 (23) ◽  
pp. 3707-3723 ◽  
Author(s):  
Anne Bertolotti
Keyword(s):  
Protein Phosphatase ◽  
Catalytic Subunit ◽  
Regulatory Subunit ◽  
Post Translational Modification ◽  
Antagonistic Action ◽  
Cellular Processes ◽  
Depth Study ◽  
Split Protein ◽  
Phosphatase System ◽  
Physiological Substrates

Reversible phosphorylation of proteins is a post-translational modification that regulates all aspect of life through the antagonistic action of kinases and phosphatases. Protein kinases are well characterized, but protein phosphatases have been relatively neglected. Protein phosphatase 1 (PP1) catalyzes the dephosphorylation of a major fraction of phospho-serines and phospho-threonines in cells and thereby controls a broad range of cellular processes. In this review, I will discuss how phosphatases were discovered, how the view that they were unselective emerged and how recent findings have revealed their exquisite selectivity. Unlike kinases, PP1 phosphatases are obligatory heteromers composed of a catalytic subunit bound to one (or two) non-catalytic subunit(s). Based on an in-depth study of two holophosphatases, I propose the following: selective dephosphorylation depends on the assembly of two components, the catalytic subunit and the non-catalytic subunit, which serves as a high-affinity substrate receptor. Because functional complementation of the two modules is required to produce a selective holophosphatase, one can consider that they are split enzymes. The non-catalytic subunit was often referred to as a regulatory subunit, but it is, in fact, an essential component of the holoenzyme. In this model, a phosphatase and its array of mostly orphan substrate receptors constitute the split protein phosphatase system. The set of potentially generalizable principles outlined in this review may facilitate the study of these poorly understood enzymes and the identification of their physiological substrates.

scholarly journals Protein phosphatase type 1 interacts with proteins required for meiosis and other cellular processes in Saccharomyces cerevisiae.

1996 ◽  
Vol 16 (8) ◽  
pp. 4199-4206 ◽  
Author(s):  
J Tu ◽  
W Song ◽  
M Carlson
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Hybrid System ◽  
Protein Phosphatase ◽  
Regulatory Subunit ◽  
Specific Substrate ◽  
Type I ◽  
Cellular Processes ◽  
Cell Extracts ◽  
Two Hybrid ◽  
Protein Phosphatase Type

Protein phosphatase type I (PP1) is involved in diverse cellular processes, and its activity toward specific substrates is thought to be controlled by different regulatory or targeting subunits. To identify regulatory subunits and substrates of the Saccharomyces cerevisiae PP1, encoded by GLC7, we used the two-hybrid system to detect interacting proteins. Among the many proteins identified were Gac1, a known glycogen regulatory subunit, and a protein with homology to Gac1. We also characterized a new gene designated GIP1, for Glc7-interacting protein. We show that a Gip1 fusion protein coimmunoprecipitates with PP1 from cell extracts. Molecular and genetic analyses indicate that GIP1 is expressed specifically during meiosis, affects transcription of late meiotic genes, and is essential for sporulation. Thus, the Gip1 protein is a candidate for a meiosis-specific substrate or regulator of PP1. Finally, we recovered two genes, RED1 and SCD5, with roles in meiosis and the vesicular secretory pathway, respectively. These results provide strong evidence implicating PP1 function in meiosis. In addition, this study indicates that the two-hybrid system offers a promising approach to understanding the multiple roles and interactions of PP1 in cellular regulation.

Protein phosphatase 2A: a highly regulated family of serine/threonine phosphatases implicated in cell growth and signalling

2001 ◽  
Vol 353 (3) ◽  
pp. 417-439 ◽  
Author(s):  
Veerle JANSSENS ◽  
Jozef GORIS
Keyword(s):  
Protein Phosphatase ◽  
Cellular Localization ◽  
Protein Phosphatase 2A ◽  
Viral Proteins ◽  
Catalytic Subunit ◽  
Post Translational Modification ◽  
Regulatory Subunits ◽  
Regulatory Ability ◽  
Phosphatase 2A ◽  
Cycle Regulation

Protein phosphatase 2A (PP2A) comprises a family of serine/threonine phosphatases, minimally containing a well conserved catalytic subunit, the activity of which is highly regulated. Regulation is accomplished mainly by members of a family of regulatory subunits, which determine the substrate specificity, (sub)cellular localization and catalytic activity of the PP2A holoenzymes. Moreover, the catalytic subunit is subject to two types of post-translational modification, phosphorylation and methylation, which are also thought to be important regulatory devices. The regulatory ability of PTPA (PTPase activator), originally identified as a protein stimulating the phosphotyrosine phosphatase activity of PP2A, will also be discussed, alongside the other regulatory inputs. The use of specific PP2A inhibitors and molecular genetics in yeast, Drosophila and mice has revealed roles for PP2A in cell cycle regulation, cell morphology and development. PP2A also plays a prominent role in the regulation of specific signal transduction cascades, as witnessed by its presence in a number of macromolecular signalling modules, where it is often found in association with other phosphatases and kinases. Additionally, PP2A interacts with a substantial number of other cellular and viral proteins, which are PP2A substrates, target PP2A to different subcellular compartments or affect enzyme activity. Finally, the de-regulation of PP2A in some specific pathologies will be touched upon.

scholarly journals High Glucose Exposure Promotes Activation of Protein Phosphatase 2A in Rodent Islets and INS-1 832/13 β-Cells by Increasing the Posttranslational Carboxylmethylation of Its Catalytic Subunit

Endocrinology ◽  
2014 ◽  
Vol 155 (2) ◽  
pp. 380-391 ◽  
Author(s):  
Daleep K. Arora ◽  
Baker Machhadieh ◽  
Andrea Matti ◽  
Brian E. Wadzinski ◽  
Sasanka Ramanadham ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Endoplasmic Reticulum Stress ◽  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Hormone Secretion ◽  
Catalytic Subunit ◽  
Regulatory Subunit ◽  
Cellular Functions ◽  
Phosphatase 2A ◽  
Normal Rat

Existing evidence implicates regulatory roles for protein phosphatase 2A (PP2A) in a variety of cellular functions, including cytoskeletal remodeling, hormone secretion, and apoptosis. We report here activation of PP2A in normal rat islets and insulin-secreting INS-1 832/13 cells under the duress of hyperglycemic (HG) conditions. Small interfering RNA-mediated knockdown of the catalytic subunit of PP2A (PP2Ac) markedly attenuated glucose-induced activation of PP2A. HG, but not nonmetabolizable 3-O-methyl glucose or mannitol (osmotic control), significantly stimulated the methylation of PP2Ac at its C-terminal Leu-309, suggesting a novel role for this posttranslational modification in glucose-induced activation of PP2A. Moreover, knockdown of the cytosolic leucine carboxymethyl transferase 1 (LCMT1), which carboxymethylates PP2Ac, significantly attenuated PP2A activation under HG conditions. In addition, HG conditions, but not 3-O-methyl glucose or mannitol, markedly increased the expression of LCMT1. Furthermore, HG conditions significantly increased the expression of B55α, a regulatory subunit of PP2A, which has been implicated in islet dysfunction under conditions of oxidative stress and diabetes. Thapsigargin, a known inducer of endoplasmic reticulum stress, failed to exert any discernible effects on the carboxymethylation of PP2Ac, expression of LCMT1 and B55α, or PP2A activity, suggesting no clear role for endoplasmic reticulum stress in HG-induced activation of PP2A. Based on these findings, we conclude that exposure of the islet β-cell to HG leads to accelerated PP2A signaling pathway, leading to loss in glucose-induced insulin secretion.

scholarly journals Methylated C-terminal leucine residue of PP2A catalytic subunit is important for binding of regulatory Bα subunit

1999 ◽  
Vol 339 (2) ◽  
pp. 241-246 ◽  
Author(s):  
Jeffrey C. BRYANT ◽  
Ryan S. WESTPHAL ◽  
Brian E. WADZINSKI
Keyword(s):  
Catalytic Subunit ◽  
Regulatory Subunit ◽  
Post Translational Modification ◽  
Regulatory Subunits ◽  
Leucine Residue ◽  
Cell Extracts ◽  
C Subunit ◽  
Phosphatase 2A ◽  
A Subunit

Methylation of the C-terminal leucine residue (Leu309) of protein serine/threonine phosphatase 2A catalytic subunit (PP2AC) is known to regulate catalytic activity in vitro, but the functional consequence(s) of this post-translational modification in the context of the cell remain unclear. Alkali-induced demethylation of PP2AC in purified PP2A heterotrimer (ABαC), but not in purified PP2A heterodimer (AC), indicated that a larger fraction of PP2AC is carboxymethylated in ABαC than in AC. To explore the role of Leu309 in PP2A holoenzyme assembly, epitope-tagged PP2A catalytic subunit (HA-PP2A) and a mutant of HA-PP2A containing an alanine residue in place of Leu309 (HA-PP2A-L309A) were transiently expressed in COS cells. Both recombinant proteins exhibited serine/threonine phosphatase activity when immunoisolated from COS cell extracts. HA-PP2A, but not HA-PP2A-L309A, was carboxymethylated in vitro. A chromatographic analysis of cell extracts indicated that most endogenous PP2AC and HA-PP2A were co-eluted with the A and Bα regulatory subunits of PP2A, whereas most HA-PP2A-L309A seemed to elute with the A subunit as a smaller complex or, alternatively, as free catalytic (C) subunit. The A subunit co-immunoisolated with both tagged proteins; however, substantially less Bα subunit co-immunoisolated with HA-PP2A-L309A than with HA-PP2A. These results demonstrate that the reversibly methylated C-terminal leucine residue of PP2AC is important for Bα regulatory subunit binding. Furthermore, the results provide evidence for an interrelationship between PP2AC carboxymethylation and PP2A holoenzyme assembly.

scholarly journals Molecular cloning and developmental expression of the catalytic and 65-kDa regulatory subunits of protein phosphatase 2A in Drosophila.

1992 ◽  
Vol 3 (3) ◽  
pp. 287-298 ◽  
Author(s):  
R E Mayer-Jaekel ◽  
S Baumgartner ◽  
G Bilbe ◽  
H Ohkura ◽  
D M Glover ◽  
...  
Keyword(s):  
Protein Phosphatase ◽  
Developmental Stages ◽  
Protein Phosphatase 2A ◽  
Catalytic Subunit ◽  
Developmental Expression ◽  
Regulatory Subunit ◽  
Predicted Amino Acid Sequence ◽  
Cdna Clones ◽  
Transcript Levels ◽  
Phosphatase 2A

cDNA clones encoding the catalytic subunit and the 65-kDa regulatory subunit of protein phosphatase 2A (PR65) from Drosophila melanogaster have been isolated by homology screening with the corresponding human cDNAs. The Drosophila clones were used to analyze the spatial and temporal expression of the transcripts encoding these two proteins. The Drosophila PR65 cDNA clones contained an open reading frame of 1773 nucleotides encoding a protein of 65.5 kDa. The predicted amino acid sequence showed 75 and 71% identity to the human PR65 alpha and beta isoforms, respectively. As previously reported for the mammalian PR65 isoforms, Drosophila PR65 is composed of 15 imperfect repeating units of approximately 39 amino acids. The residues contributing to this repeat structure show also the highest sequence conservation between species, indicating a functional importance for these repeats. The gene encoding Drosophila PR65 was located at 29B1,2 on the second chromosome. A major transcript of 2.8 kilobase (kb) encoding the PR65 subunit and two transcripts of 1.6 and 2.5 kb encoding the catalytic subunit could be detected throughout Drosophila development. All of these mRNAs were most abundant during early embryogenesis and were expressed at lower levels in larvae and adult flies. In situ hybridization of different developmental stages showed a colocalization of the PR65 and catalytic subunit transcripts. The mRNA expression is high in the nurse cells and oocytes, consistent with a high equally distributed expression in early embryos. In later embryonal development, the expression remains high in the nervous system and the gonads but the overall transcript levels decrease. In third instar larvae, high levels of mRNA could be observed in brain, imaginal discs, and in salivary glands. These results indicate that protein phosphatase 2A transcript levels change during development in a tissue and in a time-specific manner.

scholarly journals The Role of Protein Phosphatase 2A Catalytic Subunit Cα in Embryogenesis: Evidence from Sequence Analysis and Localization Studies

1999 ◽  
Vol 380 (9) ◽  
pp. 1117-1120 ◽  
Author(s):  
Jürgen Götz ◽  
Wilfried Kues
Keyword(s):  
Protein Phosphatase ◽  
Genomic Organization ◽  
Protein Phosphatase 2A ◽  
Catalytic Subunit ◽  
Regulatory Subunit ◽  
Catalytic Subunits ◽  
Regulatory Subunits ◽  
Phosphatase 2A ◽  
The Brain

AbstractProtein phosphatase 2A (PP2A) constitutes one of the major families of protein serine/threonine phosphatases found in all eukaryotic cells. PP2A holoenzymes are composed of a catalytic subunit complexed with a structural regulatory subunit of 65 kDa. These core subunits associate with regulatory subunits of various sizes to form different heterotrimers which have been purified and evaluated with regard to substrate specificity. In fully differentiated tissues PP2A expression levels are highest in the brain, however, relatively little is known about expression in the developing embryo.In order to determine the composition of PP2A catalytic subunits in the mouse, cDNAs were cloned and the genomic organization of PP2A Cα was determined.By a gene targeting approach in the mouse, we have previously shown that the absence of the major catalytic subunit of PP2A, Cα, resulted in embryonic lethality around embryonic day E6.5. No mesoderm was formed which implied that PP2A plays a crucial role in gastrulation.Here, we extended our studies and analyzed wildtype embryos for Cα expression at subsequent stages of development. After gastrulation is completed, we find high expression of Cα restricted to the neural folds, which suggests that PP2A plays an additional pivotal role in neurulation.

scholarly journals The modulator protein dissociates the catalytic subunit of hepatic protein phosphatase G from glycogen

1988 ◽  
Vol 250 (3) ◽  
pp. 659-663 ◽  
Author(s):  
M Bollen ◽  
W Stalmans
Keyword(s):  
Phosphatase Activity ◽  
Rat Liver ◽  
Protein Phosphatase ◽  
Soluble Fraction ◽  
Glycogen Synthase ◽  
Gel Filtration ◽  
Catalytic Subunit ◽  
Regulatory Subunit ◽  
Phosphatase Activities ◽  
Glycogen Particles

1. The phosphorylase phosphatase and glycogen-synthase phosphatase activities associated with the glycogen particles from rat liver were progressively inhibited by incubation with modulator protein. However, the phosphorylase phosphatase activity of the catalytic subunit was entirely recovered after destruction of the modulator and the regulatory subunit(s) by trypsin. 2. Inhibition of protein phosphatase G by modulator was associated with a translocation of the phosphorylase phosphatase activity (measured after incubation with trypsin) from glycogen to the soluble fraction. The degree of inhibition of phosphatase G corresponded closely to the extent to which the phosphorylase phosphatase activity was released from the glycogen particles. Incubation of glycogen-free protein phosphatase G with modulator did not change the affinity of the enzyme for added glycogen, but decreased the amount of phosphatase that could be bound to glycogen. 3. The phosphorylase phosphatase activity that was released from the glycogen particles by modulator migrated on gel filtration as a complex (Mr 106,000) of the catalytic subunit with modulator. Phosphorylase phosphatase activity could be transferred from glycogen-bound protein phosphatase G to modulator that was covalently bound to Sepharose. After elution from the column, the enzyme was identified as the free catalytic subunit (Mr 37,000).

scholarly journals Developmental Expression of Protein Phosphatase 2A in the Kidney

1999 ◽  
Vol 10 (8) ◽  
pp. 1737-1745
Author(s):  
ALLEN D. EVERETT ◽  
CHUN XUE ◽  
TAMARA STOOPS
Keyword(s):  
Signal Transduction ◽  
Protein Phosphatase ◽  
Kidney Development ◽  
Developmental Regulation ◽  
Protein Phosphatase 2A ◽  
Catalytic Subunit ◽  
Developmental Expression ◽  
Regulatory Subunit ◽  
Northern Analysis ◽  
Phosphatase 2A

Abstract. Although a number of growth and transcription factors are known to regulate renal growth and development, the signal transduction molecules necessary to mediate these developmental signals are relatively unknown. Therefore, the activity and mRNA and protein expression of the signal transduction molecule protein phosphatase 2A (PP2A) were examined during rat kidney development. Northern analysis of total kidney RNA or Western analysis of kidney protein homogenates from embryonic day 15 to 90-d-old adults demonstrated developmental regulation of the catalytic, major 55-kD B regulatory subunit and A structural subunit with the highest levels of expression in late embryonic and newborn kidneys. Similarly, okadaic acid-inhibitable phosphatase enzyme activity was highest in the embryonic and newborn kidney. To map cell-specific expression of PP2A in the developing kidney, in situ hybridization with a catalytic subunit digoxigenin-labeled cRNA was performed on embryonic day 20 and newborn kidneys. PP2A was found predominately in the nephrogenic cortex and particularly in the developing glomeruli and nonbrush border tubules in the embryonic day 20 and newborn kidneys. Similarly, immunocytochemistry with a specific PP2A catalytic subunit polyclonal anti-peptide antibody demonstrated catalytic subunit protein particularly concentrated in the podocytes of glomeruli in the newborn kidney. In the adult kidney, PP2A protein was no longer detectable except in the nuclei of distal tubular cells. Therefore, the developmental regulation of PP2A activity and protein during kidney development and its mapping to the nephrogenic cortex, developing glomeruli, and tubules suggests a role for PP2A in the regulation of nephron growth and differentiation.

scholarly journals Protein phosphatase 4 catalytic subunit regulates Cdk1 activity and microtubule organization via NDEL1 dephosphorylation

2008 ◽  
Vol 180 (6) ◽  
pp. 1133-1147 ◽  
Author(s):  
Kazuhito Toyo-oka ◽  
Daisuke Mori ◽  
Yoshihisa Yano ◽  
Masayuki Shiota ◽  
Hiroshi Iwao ◽  
...  
Keyword(s):  
Protein Phosphatase ◽  
Tumor Necrosis ◽  
Regulatory Mechanism ◽  
Catalytic Subunit ◽  
Related Protein ◽  
Microtubule Organization ◽  
Targeted Disruption ◽  
Cellular Processes ◽  
Tumor Necrosis Factor Signaling ◽  
Necrosis Factor

Protein phosphatase 4 catalytic subunit (PP4c) is a PP2A-related protein serine/threonine phosphatase with important functions in a variety of cellular processes, including microtubule (MT) growth/organization, apoptosis, and tumor necrosis factor signaling. In this study, we report that NDEL1 is a substrate of PP4c, and PP4c selectively dephosphorylates NDEL1 at Cdk1 sites. We also demonstrate that PP4c negatively regulates Cdk1 activity at the centrosome. Targeted disruption of PP4c reveals disorganization of MTs and disorganized MT array. Loss of PP4c leads to an unscheduled activation of Cdk1 in interphase, which results in the abnormal phosphorylation of NDEL1. In addition, abnormal NDEL1 phosphorylation facilitates excessive recruitment of katanin p60 to the centrosome, suggesting that MT defects may be attributed to katanin p60 in excess. Inhibition of Cdk1, NDEL1, or katanin p60 rescues the defective MT organization caused by PP4 inhibition. Our work uncovers a unique regulatory mechanism of MT organization by PP4c through its targets Cdk1 and NDEL1 via regulation of katanin p60 distribution.

scholarly journals A Newborn with Severe Ventriculomegaly: Expanding the PPP2R1A Gene Mutation Phenotype

2019 ◽  
Vol 08 (04) ◽  
pp. 240-243
Author(s):  
Alexandra Wallace ◽  
Paul Caruso ◽  
Amel Karaa
Keyword(s):  
Corpus Callosum ◽  
Gene Mutation ◽  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Catalytic Subunit ◽  
Regulatory Subunit ◽  
Pontocerebellar Hypoplasia ◽  
Genetic Condition ◽  
Diverse Range ◽  
Phosphatase 2A

AbstractProtein phosphatase 2A (PP2A) is a heterotrimeric protein serine/threonine phosphatase that regulates a diverse range of cellular activities. The PPP2R1A gene on chromosome 19 (19q13.41) encodes the α isoform of the scaffolding subunit of the PP2A holoenzyme, which functions to link the catalytic subunit to the regulatory subunit. Here we present a case of a newborn boy with a novel PPP2R1A gene mutation (c.548G>A; p.Arg183Gln) with severe lateral and third ventriculomegaly, hypoplastic corpus callosum, and pontocerebellar hypoplasia. To our knowledge, this is the sixth case reported in the literature, thus expanding the phenotype of this rare genetic condition.

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