scholarly journals Methylated PP2A stabilizes Gcn4 to enable a methionine-induced anabolic program

2020 ◽  
Vol 295 (52) ◽  
pp. 18390-18405
Author(s):  
Adhish S. Walvekar ◽  
Ganesh Kadamur ◽  
Sreesa Sreedharan ◽  
Ritu Gupta ◽  
Rajalakshmi Srinivasan ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Carbon Metabolism ◽  
Protein Phosphatase ◽  
Ribosome Biogenesis ◽  
Stable State ◽  
High Cell ◽  
Nucleotide Biosynthesis ◽  
Protein Levels ◽  
Phosphatase 2A ◽  
Metabolic Precursors

Methionine, through S-adenosylmethionine, activates a multifaceted growth program in which ribosome biogenesis, carbon metabolism, and amino acid and nucleotide biosynthesis are induced. This growth program requires the activity of the Gcn4 transcription factor (called ATF4 in mammals), which facilitates the supply of metabolic precursors that are essential for anabolism. However, how Gcn4 itself is regulated in the presence of methionine is unknown. Here, we discover that Gcn4 protein levels are increased by methionine, despite conditions of high cell growth and translation (in which the roles of Gcn4 are not well-studied). We demonstrate that this mechanism of Gcn4 induction is independent of transcription, as well as the conventional Gcn2/eIF2α-mediated increased translation of Gcn4. Instead, when methionine is abundant, Gcn4 phosphorylation is decreased, which reduces its ubiquitination and therefore degradation. Gcn4 is dephosphorylated by the protein phosphatase 2A (PP2A); our data show that when methionine is abundant, the conserved methyltransferase Ppm1 methylates and alters the activity of the catalytic subunit of PP2A, shifting the balance of Gcn4 toward a dephosphorylated, stable state. The absence of Ppm1 or the loss of the PP2A methylation destabilizes Gcn4 even when methionine is abundant, leading to collapse of the Gcn4-dependent anabolic program. These findings reveal a novel, methionine-dependent signaling and regulatory axis. Here methionine directs the conserved methyltransferase Ppm1 via its target phosphatase PP2A to selectively stabilize Gcn4. Through this, cells conditionally modify a major phosphatase to stabilize a metabolic master regulator and drive anabolism.

scholarly journals Methylated PP2A stabilizes Gcn4 to enable a methionine-induced anabolic program

2020 ◽  
Author(s):  
Adhish S. Walvekar ◽  
Ganesh Kadamur ◽  
Sreesa Sreedharan ◽  
Ritu Gupta ◽  
Rajalakshmi Srinivasan ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Amino Acid ◽  
Carbon Metabolism ◽  
Protein Phosphatase ◽  
Ribosome Biogenesis ◽  
Catalytic Subunit ◽  
Master Regulator ◽  
Nucleotide Biosynthesis ◽  
Induction Mechanism ◽  
Precursor Supply

AbstractMethionine, through S-adenosylmethionine, activates multifaceted growth programs where ribosome biogenesis, carbon metabolism, amino acid and nucleotide biosynthesis are induced. This growth program requires activity of the Gcn4 transcription factor (called ATF4 in mammals), which enables metabolic precursor supply essential for anabolism. Here, we discover how the Gcn4 protein is induced by methionine, despite conditions of high translation and anabolism. This induction mechanism is independent of transcription, as well as the conventional Gcn2/eIF2α mediated increased translation of Gcn4. Instead, when methionine is abundant, Gcn4 ubiqitination and therefore degradation is reduced, due to the decreased phosphorylation of this protein. This Gcn4 stabilization is mediated by the activity of the conserved methyltransferase, Ppm1, which specifically methylates the catalytic subunit of protein phosphatase PP2A when methionine is abundant. This methylation of PP2A shifts the balance of Gcn4 to a dephosphorylated state, which stabilizes the protein. The loss of Ppm1, or PP2A-methylation destabilizes Gcn4 when methionine is abundant, and the Gcn4-dependent anabolic program collapses. These findings reveal a novel signaling and regulatory axis, where methionine directs a conserved methyltransferase Ppm1, via its target phosphatase PP2A, to selectively stabilize Gcn4. Thereby, when methionine is abundant, cells conditionally modify a major phosphatase in order to stabilize a metabolic master-regulator and drive anabolism.

scholarly journals HSP105 Recruits Protein Phosphatase 2A To Dephosphorylate β-Catenin

2015 ◽  
Vol 35 (8) ◽  
pp. 1390-1400 ◽  
Author(s):  
Nancy Yu ◽  
Michael Kakunda ◽  
Victoria Pham ◽  
Jennie R. Lill ◽  
Pan Du ◽  
...  
Keyword(s):  
Protein Phosphatase ◽  
Target Gene ◽  
Target Genes ◽  
Glycogen Synthase ◽  
Protein Phosphatase 2A ◽  
Breast Cancer Patients ◽  
Poor Overall Survival ◽  
Protein Levels ◽  
Phosphatase 2A ◽  
Unidentified Component

The Wnt/β-catenin pathway causes accumulation of β-catenin in the cytoplasm and its subsequent translocation into the nucleus to initiate the transcription of the target genes. Without Wnt stimulation, β-catenin forms a complex with axin (axis inhibitor), adenomatous polyposis coli (APC), casein kinase 1α (CK1α), and glycogen synthase kinase 3β (GSK3β) and undergoes phosphorylation-dependent ubiquitination. Phosphatases, such as protein phosphatase 2A (PP2A), interestingly, also are components of this degradation complex; therefore, a balance must be reached between phosphorylation and dephosphorylation. How this balance is regulated is largely unknown. Here we show that a heat shock protein, HSP105, is a previously unidentified component of the β-catenin degradation complex. HSP105 is required for Wnt signaling, since depletion of HSP105 compromises β-catenin accumulation and target gene transcription upon Wnt stimulation. Mechanistically, HSP105 depletion disrupts the integration of PP2A into the β-catenin degradation complex, favoring the hyperphosphorylation and degradation of β-catenin. HSP105 is overexpressed in many types of tumors, correlating with increased nuclear β-catenin protein levels and Wnt target gene upregulation. Furthermore, overexpression of HSP105 is a prognostic biomarker that correlates with poor overall survival in breast cancer patients as well as melanoma patients participating in the BRIM2 clinical study.

Abstract 466: Protein Phosphatase 2A and c-Myc as Intracellular Messengers in the Natriuretic Renal Dopaminergic System

Hypertension ◽  
2013 ◽  
Vol 62 (suppl_1) ◽  
Author(s):  
Hanh T Tran ◽  
John J Gildea ◽  
Robin A Felder
Keyword(s):  
G Protein ◽  
Protein Phosphatase ◽  
Sodium Excretion ◽  
Protein Phosphatase 2A ◽  
Camp Accumulation ◽  
Receptor Kinase ◽  
G Protein Coupled Receptor ◽  
Protein Levels ◽  
Phosphatase 2A ◽  
G Protein Coupled

G protein-coupled receptor kinase 4 (GRK4) is known to negatively regulate the dopamine-1 receptor (D 1 R) in human renal proximal tubule cells (RPTC) leading to reduced sodium excretion. c-Myc is a transcription factor involved in positive regulation of G protein-coupled receptor kinase 4 (GRK4). Protein phosphatase 2A (PP2A) inhibits c-Myc by dephosphorylating a residue that normally stabilizes c-Myc. We have previously shown that stimulation of the natriuretic D 1 R in RPTC led to an increased ratio of PP2A/c-Myc binding. Treatment with PMA (protein kinase C inhibitor) led to a decreased PP2A/c-Myc ratio and a lack of cAMP accumulation after stimulation with fenoldopam (FEN, D 1 R agonist). We hypothesized that PP2A plays a key role in regulating natriuresis and that perturbation of PP2A would directly have effects on protein levels of c-Myc, the ratio of PP2A/c-Myc, and the accumulation of cAMP. We used normal RPTCs (nRPTC) and RPTCs that have an uncoupled D 1 R that no longer stimulates adenylyl cyclase (uRPTC). Inhibition of PP2A in uRPTCs with okadaic acid (OA, 100nM, 3 hr) caused an increase in c-Myc protein levels (97.8% ± 18.9 SEM; n=6; p<0.05 (1.44 / 0.73 RFU)), a decrease in the PP2A/c-Myc ratio (-81.8% ± 1.5 SEM; n=6; p<0.05 (1.42 /7.82 RFU)), and a lack of cAMP accumulation upon treatment with SKF38393 (a D 1 R agonist similar to FEN). Activation of PP2A with FTY720 (PP2A activator, 10μM, 3hr) caused a decrease in c-Myc protein levels (- 85.4% ± 2.3 SEM; n=6; p<0.005 (0.11/ 0.73 RFU)), an increase in the PP2A/c-Myc binding ratio by 345.3% ± 90.3 SEM; n=6; p<0.01 (34.82/ 7.82 RFU), and an increase in cAMP accumulation upon stimulation with SKF38393 (94.0% ± 12.4 SEM; n=3; p<0.05 (9.04/4.66 pmole cAMP/mg protein) compared to VEH. In summary, the D 1 R coupling defect found in uRPTCs was restored through activation of PP2A and inhibition of c-Myc. We conclude that PP2A interacts with c-Myc to regulate the natriuretic effect of the D 1 R providing additional insight into the intracellular regulatory events surrounding sodium excretion.

scholarly journals Protein phosphatase 2A, complement component 4, and APOE genotype linked to Alzheimer’s disease using a systems biology approach

2020 ◽  
Author(s):  
Gyungah R. Jun ◽  
Yang You ◽  
Congcong Zhu ◽  
Gaoyuan Meng ◽  
Jaeyoon Chung ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Prefrontal Cortex ◽  
Protein Phosphatase ◽  
Gene Network ◽  
Protein Phosphatase 2A ◽  
Tau Pathology ◽  
Culture Experiment ◽  
Protein Levels ◽  
Phosphatase 2A

ABSTRACTBackgroundRecent reports suggest that the rare apolipoprotein E (APOE) Christchurch mutation and ε2 allele protect against Alzheimer’s disease (AD) pathology by reducing the burden of tau pathology. However, the mechanism(s) underlying the ε2 protective effect linking to tau is largely unknown.MethodsThe role of the ε2 allele in Alzheimer’s disease (AD) was investigated a genome-wide association study (GWAS) for AD among 2,120 ε2 carriers from the Alzheimer Disease Genetics Consortium (ADGC), and then prioritized by gene network analysis, differential gene expression analysis at tissue- and cell-levels as well as methylation profiling of CpG sites, in prefrontal cortex tissue from 761 brains of the Religious Orders Study and Memory and Aging Project (ROSMAP) and the Framingham Heart Study (FHS), Boston University Alzheimer’s Disease Center (BUADC). The levels of two catalytic subunit proteins from protein phosphatase 2A (PPP2CA and PPP2CB) were validated in prefrontal cortex area of 193 of the FHS/BUADC brains. The findings from human autopsied brains were further validated by a co-culture experiment of human isogenic APOE induced pluripotent stem cell (iPSC) derived neurons and astrocytes.ResultsOf the significantly associated loci with AD among APOE ε2 carriers (P<10−6), PPP2CB (P=1.1×10−7) was the key node in the APOE ε2-related gene network and contained the most significant CpG site (P=7.3×10−4) located 2,814 base pair upstream of the top-ranked GWAS variant. Among APOE ε3/ε4 subjects, the level of Aβ42 was negatively correlated with protein levels of PPP2CA (P=9.9×10−3) and PPP2CB (P=2.4×10−3), and PPP2CA level was correlated with the level of pTau231 level (P=5.3×10−3). Significant correlations were also observed for PPP2CB with complement 4B (C4B) protein levels (P=3.3×10−7) and PPP2CA with cross reactive protein (CRP) levels (P=6.4×10−4). C1q level was not associated with Aβ42, pTau231, PPP2CB, or C4B levels. We confirmed the significant correlation of PPP2CB expression with pTau231/tTau ratio (P=0.01) and C4A/B (P=2.0×10−4) expression observed in brain tissue in a co-culture experiment of iPSC derived neurons and astrocytes.ConclusionWe demonstrated for the first time a molecular link between a tau phosphatase and the classical complement pathway, especially C4, and AD-related tau pathology.

Decreased expression of microRNA-199b increases protein levels of SET (protein phosphatase 2A inhibitor) in human choriocarcinoma

2010 ◽  
Vol 291 (1) ◽  
pp. 99-107 ◽  
Author(s):  
Angel Chao ◽  
Chia-Lung Tsai ◽  
Pei-Chi Wei ◽  
Swei Hsueh ◽  
An-Shine Chao ◽  
...  
Keyword(s):  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Protein Levels ◽  
Phosphatase 2A

scholarly journals B56α/Protein Phosphatase 2A Inhibits Adipose Lipolysis in High-Fat Diet-Induced Obese Mice

Endocrinology ◽  
2010 ◽  
Vol 151 (8) ◽  
pp. 3624-3632 ◽  
Author(s):  
Brice P. Kinney ◽  
Liping Qiao ◽  
Justin M. LeVaugh ◽  
Jianhua Shao
Keyword(s):  
Protein Kinase ◽  
Protein Kinase A ◽  
Protein Phosphatase ◽  
High Fat Diet ◽  
Protein Phosphatase 2A ◽  
High Fat ◽  
Protein Levels ◽  
Epididymal Fat ◽  
Phosphatase 2A ◽  
Kinase A

Lipolysis and lipogenesis are two opposite processes that control lipid storage in adipocytes. Impaired adipose lipolysis has been observed in both obese human subjects and animal models. This study investigated the mechanisms underlying impaired adipose lipolysis in a high-fat diet-induced obese (DIO) mouse model. DIO models were created using male C57BL/6 mice. Our results show that β3 adrenergic receptor-specific agonist BRL37344 induced adipose lipolysis was significantly blunted in DIO mice. The levels of Ser660 phosphorylation of hormone-sensitive lipase (HSL) were significantly decreased in the epididymal fat of DIO mice. However, protein levels of HSL, adipose triglyceride lipase and its coactivator comparative gene identification-58 were similar between DIO and control mice. It is known that upon lipolytic hormone stimulation, protein kinase A phosphorylates HSL Ser660 and activates HSL, whereas protein phosphatase 2A (PP2A) dephosphorylates and inactivates HSL. Interestingly, our study shows that high-fat feeding did not alter epididymal fat cAMP and protein kinase A protein levels but significantly increased the expression of the α-isoform of PP2A regulatory subunit B′ (B56α). To study the role of B56α in obesity-associated lipolytic defect, B56α was overexpressed or knocked down by adenovirus-mediated gene transduction in cultured 3T3-L1CARΔ1 adipocytes. Overexpression of B56α significantly decreased HSL Ser660 phosphorylation. In contrast, knocking down B56α increased hormone-stimulated HSL activation and lipolysis in mature 3T3-L1CARΔ1 adipocytes. These results strongly suggest that elevated B56α/PP2A inhibits HSL and lipolysis in white adipose tissue of DIO mice.

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