scholarly journals Protein phosphatase 2A is crucial for sarcomere organization in Caenorhabditis elegans striated muscle

2018 ◽  
Vol 29 (17) ◽  
pp. 2084-2097 ◽  
Author(s):  
Hiroshi Qadota ◽  
Yohei Matsunaga ◽  
Pritha Bagchi ◽  
Karen I. Lange ◽  
Karma J. Carrier ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Protein Phosphatase ◽  
Striated Muscle ◽  
Muscle Protein ◽  
Protein Phosphatase 2A ◽  
Regulatory Subunit ◽  
Loss Of Function ◽  
Double Line ◽  
Regulatory Subunits ◽  
Phosphatase 2A

Protein phosphatase 2A (PP2A) is a heterotrimer composed of single catalytic and scaffolding subunits and one of several possible regulatory subunits. We identified PPTR-2, a regulatory subunit of PP2A, as a binding partner for the giant muscle protein UNC-89 (obscurin) in Caenorhabditis elegans. PPTR-2 is required for sarcomere organization when its paralogue, PPTR-1, is deficient. PPTR-2 localizes to the sarcomere at dense bodies and M-lines, colocalizing with UNC-89 at M-lines. PP2A components in C. elegans include one catalytic subunit LET-92, one scaffolding subunit (PAA-1), and five regulatory subunits (SUR-6, PPTR-1, PPTR-2, RSA-1, and CASH-1). In adult muscle, loss of function in any of these subunits results in sarcomere disorganization. rsa-1 mutants show an interesting phenotype: one of the two myosin heavy chains, MHC A, localizes as closely spaced double lines rather than single lines. This “double line” phenotype is found in rare missense mutants of the head domain of MHC B myosin, such as unc-54(s74). Analysis of phosphoproteins in the unc-54(s74) mutant revealed two additional phosphoserines in the nonhelical tailpiece of MHC A. Antibodies localize PPTR-1, PAA-1, and SUR-6 to I-bands and RSA-1 to M-lines and I-bands. Therefore, PP2A localizes to sarcomeres and functions in the assembly or maintenance of sarcomeres.

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 Localization of Saccharomyces cerevisiae Protein Phosphatase 2A Subunits throughout Mitotic Cell Cycle

2002 ◽  
Vol 13 (10) ◽  
pp. 3477-3492 ◽  
Author(s):  
Matthew S. Gentry ◽  
Richard L. Hallberg
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Cycle ◽  
Protein Phosphatase ◽  
Fluorescent Protein ◽  
Protein Phosphatase 2A ◽  
Mitotic Cell ◽  
Regulatory Subunit ◽  
Regulatory Subunits ◽  
C Subunit ◽  
Phosphatase 2A

Protein phosphatase 2A (PP2A) regulates a broad spectrum of cellular processes. This enzyme is a collection of varied heterotrimeric complexes, each composed of a catalytic (C) and regulatory (B) subunit bound together by a structural (A) subunit. To understand the cell cycle dynamics of this enzyme population, we carried out quantitative and qualitative analyses of the PP2A subunits of Saccharomyces cerevisiae. We found the following: the level of each subunit remained constant throughout the cell cycle; there is at least 10 times more of one of the regulatory subunits (Rts1p) than the other (Cdc55p); Tpd3p, the structural subunit, is limiting for both catalytic and regulatory subunit binding. Using green fluorescent protein-tagged forms of each subunit, we monitored the sites of significant accumulation of each protein throughout the cell cycle. The two regulatory subunits displayed distinctly different dynamic localization patterns that overlap with the A and C subunits at the bud tip, kinetochore, bud neck, and nucleus. Using strains null for single subunit genes, we confirmed the hypothesis that regulatory subunits determine sites of PP2A accumulation. Although Rts1p and Tpd3p required heterotrimer formation to achieve normal localization, Cdc55p achieved its normal localization in the absence of either an A or C subunit.

scholarly journals Reduction of protein phosphatase 2A (PP2A) complexity reveals cellular functions and dephosphorylation motifs of the PP2A/B′δ holoenzyme

2020 ◽  
Vol 295 (17) ◽  
pp. 5654-5668 ◽  
Author(s):  
Chian Ju Jong ◽  
Ronald A. Merrill ◽  
Emily M. Wilkerson ◽  
Laura E. Herring ◽  
Lee M. Graves ◽  
...  
Keyword(s):  
Substrate Specificity ◽  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Second Messengers ◽  
Phosphorylation Site ◽  
Regulatory Subunit ◽  
Regulatory Subunits ◽  
Endogenous Expression ◽  
Phosphatase 2A ◽  
B Subunits

Protein phosphatase 2A (PP2A) is a large enzyme family responsible for most cellular Ser/Thr dephosphorylation events. PP2A substrate specificity, localization, and regulation by second messengers rely on more than a dozen regulatory subunits (including B/R2, B′/R5, and B″/R3), which form the PP2A heterotrimeric holoenzyme by associating with a dimer comprising scaffolding (A) and catalytic (C) subunits. Because of partial redundancy and high endogenous expression of PP2A holoenzymes, traditional approaches of overexpressing, knocking down, or knocking out PP2A regulatory subunits have yielded only limited insights into their biological roles and substrates. To this end, here we sought to reduce the complexity of cellular PP2A holoenzymes. We used tetracycline-inducible expression of pairs of scaffolding and regulatory subunits with complementary charge-reversal substitutions in their interaction interfaces. For each of the three regulatory subunit families, we engineered A/B charge–swap variants that could bind to one another, but not to endogenous A and B subunits. Because endogenous Aα was targeted by a co-induced shRNA, endogenous B subunits were rapidly degraded, resulting in expression of predominantly a single PP2A heterotrimer composed of the A/B charge–swap pair and the endogenous catalytic subunit. Using B′δ/PPP2R5D, we show that PP2A complexity reduction, but not PP2A overexpression, reveals a role of this holoenzyme in suppression of extracellular signal–regulated kinase signaling and protein kinase A substrate dephosphorylation. When combined with global phosphoproteomics, the PP2A/B′δ reduction approach identified consensus dephosphorylation motifs in its substrates and suggested that residues surrounding the phosphorylation site play roles in PP2A substrate specificity.

scholarly journals Methylation of the Protein Phosphatase 2A Catalytic Subunit Is Essential for Association of Bα Regulatory Subunit But Not SG2NA, Striatin, or Polyomavirus Middle Tumor Antigen

2001 ◽  
Vol 12 (1) ◽  
pp. 185-199 ◽  
Author(s):  
Xing Xian Yu ◽  
Xianxing Du ◽  
Carlos S. Moreno ◽  
Richard E. Green ◽  
Egon Ogris ◽  
...  
Keyword(s):  
Tumor Antigen ◽  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Methylation Status ◽  
Regulatory Subunit ◽  
Regulatory Subunits ◽  
C Subunit ◽  
Phosphatase 2A ◽  
Carboxy Terminal

Binding of different regulatory subunits and methylation of the catalytic (C) subunit carboxy-terminal leucine 309 are two important mechanisms by which protein phosphatase 2A (PP2A) can be regulated. In this study, both genetic and biochemical approaches were used to investigate regulation of regulatory subunit binding by C subunit methylation. Monoclonal antibodies selectively recognizing unmethylated C subunit were used to quantitate the methylation status of wild-type and mutant C subunits. Analysis of 13 C subunit mutants showed that both carboxy-terminal and active site residues are important for maintaining methylation in vivo. Severe impairment of methylation invariably led to a dramatic decrease in Bα subunit binding but not of striatin, SG2NA, or polyomavirus middle tumor antigen (MT) binding. In fact, most unmethylated C subunit mutants showed enhanced binding to striatin and SG2NA. Certain carboxy-terminal mutations decreased Bα subunit binding without greatly affecting methylation, indicating that Bα subunit binding is not required for a high steady-state level of C subunit methylation. Demethylation of PP2A in cell lysates with recombinant PP2A methylesterase greatly decreased the amount of C subunit that could be coimmunoprecipitated via the Bα subunit but not the amount that could be coimmunoprecipitated with Aα subunit or MT. When C subunit methylation levels were greatly reduced in vivo, Bα subunits were found complexed exclusively to methylated C subunits, whereas striatin and SG2NA in the same cells bound both methylated and unmethylated C subunits. Thus, C subunit methylation is critical for assembly of PP2A heterotrimers containing Bα subunit but not for formation of heterotrimers containing MT, striatin, or SG2NA. These findings suggest that methylation may be able to selectively regulate the association of certain regulatory subunits with the A/C heterodimer.

scholarly journals Protein Phosphatase 2A (PP2A) Regulatory Subunits ParA and PabA Orchestrate Septation and Conidiation and Are Essential for PP2A Activity in Aspergillus nidulans

2014 ◽  
Vol 13 (12) ◽  
pp. 1494-1506 ◽  
Author(s):  
Guo-wei Zhong ◽  
Ping Jiang ◽  
Wei-ran Qiao ◽  
Yuan-wei Zhang ◽  
Wen-fan Wei ◽  
...  
Keyword(s):  
Aspergillus Nidulans ◽  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Hyphal Growth ◽  
Negative Regulator ◽  
Regulatory Subunit ◽  
Content Type ◽  
Regulatory Subunits ◽  
Pp2a Activity ◽  
Phosphatase 2A

ABSTRACTProtein phosphatase 2A (PP2A) is a major intracellular protein phosphatase that regulates multiple aspects of cell growth and metabolism. Different activities of PP2A and subcellular localization are determined by its regulatory subunits. Here we identified and characterized the functions of two protein phosphatase regulatory subunit homologs, ParA and PabA, inAspergillus nidulans. Our results demonstrate that ParA localizes to the septum site and that deletion ofparAcauses hyperseptation, while overexpression ofparAabolishes septum formation; this suggests that ParA may function as a negative regulator of septation. In comparison, PabA displays a clear colocalization pattern with 4′,6-diamidino-2-phenylindole (DAPI)-stained nuclei, and deletion ofpabAinduces a remarkable delayed-septation phenotype. BothparAandpabAare required for hyphal growth, conidiation, and self-fertilization, likely to maintain normal levels of PP2A activity. Most interestingly,parAdeletion is capable of suppressing septation defects inpabAmutants, suggesting that ParA counteracts PabA during the septation process. In contrast, double mutants ofparAandpabAled to synthetic defects in colony growth, indicating that ParA functions synthetically with PabA during hyphal growth. Moreover, unlike the case for PP2A-Par1 and PP2A-Pab1 in yeast (which are negative regulators that inactivate the septation initiation network [SIN]), loss of ParA or PabA fails to suppress defects of temperature-sensitive mutants of the SEPH kinase of the SIN. Thus, our findings support the previously unrealized evidence that the B-family subunits of PP2A have comprehensive functions as partners of heterotrimeric enzyme complexes of PP2A, both spatially and temporally, inA. nidulans.

scholarly journals B56 Regulatory Subunit of Protein Phosphatase 2A Mediates Valproic Acid-Induced p300 Degradation

2005 ◽  
Vol 25 (2) ◽  
pp. 525-532 ◽  
Author(s):  
Jihong Chen ◽  
Jonathan R. St-Germain ◽  
Qiao Li
Keyword(s):  
Valproic Acid ◽  
Transcriptional Activation ◽  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Regulatory Subunit ◽  
Interaction Domain ◽  
Regulatory Subunits ◽  
Subunit Expression ◽  
Phosphatase 2A ◽  
The Stability

ABSTRACT Transcriptional coactivator p300 is required for embryonic development and cell proliferation. Valproic acid, a histone deacetylase inhibitor, is widely used in the therapy of epilepsy and bipolar disorder. However, it has intrinsic teratogenic activity through unidentified mechanisms. We report that valproic acid stimulates proteasome-dependent p300 degradation through augmentation of gene expression of the B56γ regulatory subunits of protein phosphatase 2A. The B56γ3 regulatory and catalytic subunits of protein phosphatase 2A interact with p300. Overexpression of the B56γ3 subunit leads to proteasome-mediated p300 degradation and represses p300-dependent transcriptional activation, which requires the B56γ3 interaction domain of p300. Conversely, silencing of the B56γ subunit expression by RNA interference increases the stability and transcriptional activity of the coactivator. Our study establishes the functional interaction between protein phosphatase 2A and p300 activity and provides direct evidence for signal-dependent control of p300 function.

scholarly journals Structure and expression of a 72-kDa regulatory subunit of protein phosphatase 2A. Evidence for different size forms produced by alternative splicing

1993 ◽  
Vol 268 (20) ◽  
pp. 15267-15276
Author(s):  
P. Hendrix ◽  
R.E. Mayer-Jackel ◽  
P. Cron ◽  
J. Goris ◽  
J. Hofsteenge ◽  
...  
Keyword(s):  
Alternative Splicing ◽  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Regulatory Subunit ◽  
Phosphatase 2A
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