scholarly journals Progesterone decreases tyrosine hydroxylase phosphorylation state and increases protein phosphatase 2A activity in the stalk-median eminence on proestrous afternoon

2009 ◽  
Vol 204 (2) ◽  
pp. 209-219 ◽  
Author(s):  
Bin Liu ◽  
Lydia A Arbogast
Keyword(s):  
Tyrosine Hydroxylase ◽  
Median Eminence ◽  
Protein Phosphatase ◽  
Time Course ◽  
Protein Phosphatase 2A ◽  
Plasma Prolactin ◽  
Phosphorylation State ◽  
Pp2a Activity ◽  
Phosphatase 2A ◽  
Camp Levels

The progesterone (P4) rise on proestrous afternoon is associated with dephosphorylation of tyrosine hydroxylase (TH) and reduced TH activity in the stalk-median eminence (SME), which contributes to the proestrous prolactin surge in rats. In the present study, we investigated the time course for P4 effect on TH activity and phosphorylation state, as well as cAMP levels and protein phosphatase 2A (PP2A) activity and quantity, in the SME on proestrous morning and afternoon. P4 (7.5 mg/kg, s.c.) treatment on proestrous afternoon decreased TH activity and TH phosphorylation state at Ser-31 and Ser-40 within 1 h, whereas morning administration of P4 had no 1 h effect on TH. PP2A activity in the SME was enhanced after P4 treatment for 1 h on proestrous afternoon without a change in PP2A catalytic subunit quantity, whereas P4 treatment had no effect on PP2A activity or quantity on proestrous morning. cAMP levels in the SME were unchanged with 1 h P4 treatment. At 5 h after P4 treatment, TH activity and phosphorylation state declined coincident with an increase in plasma prolactin in both P4-treated morning and afternoon groups. PP2A activity in the SME was unchanged in 5 h P4-treated rat. Our data suggest that P4 action on tuberoinfundibular dopaminergic (TIDA) neurons involves at least two components. A more rapid (1 h) P4 effect engaged only on proestrous afternoon likely involves the activation of PP2A. The longer P4 action on TIDA neurons is evident on both the morning and afternoon of proestrus and may involve a common, as yet unidentified, mechanism.

Abstract 229: Novel Plasma Membrane Beta Adrenergic Receptor Resensitization By Protein Phosphatase 2a

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Neelakantan T Vasudevan ◽  
Anita Shukla ◽  
Sathyamangla V Naga Prasad
Keyword(s):  
Plasma Membrane ◽  
Protein Phosphatase ◽  
Adrenergic Receptor ◽  
Protein Phosphatase 2A ◽  
Metabolic Labeling ◽  
Specific Expression ◽  
Pp2a Activity ◽  
Pi3k Activity ◽  
Phosphatase 2A

Resensitization of β-adrenergic receptor (βAR) occurs by dephosphorylation of the internalized βAR by protein phosphatase 2A (PP2A) before being recycled back to plasma membrane (PM). Contrary to this classical paradigm, cardiac specific expression of inactive PI3Kγ (PI3Kγ inact ) leads to receptor resensitization at the plasma membrane as measured by adenylyl cyclase activity in mice chronically treated with the agonist. We hypothesized that PI3K activity inhibits PM receptor resensitization. Using cells stably expressing FLAG-β 1 AR alone (single) or along with PI3Kγ inact (double), we show that inhibition of PI3K activity results in novel PM receptor resensitization. Agonist activation of single stables showed significant receptor desensitization as measured by reduced cAMP generation (35.6 ± 4.6 pmol/mg protein). In contrast, double-or wortmannin (Wort, PI3K inhibitor) pre-treated single- stables showed marked generation of cAMP (87.4 ± 3.2 or 83.1 ± 5.7) showing β 1 AR resensitization. Agonist stimulation of metabolically labeled β 1 ARs pre-treated with inhibitors of internalization, sucrose and β-cyclodextrin resulted in accumulation of phosphorylated receptors at the PM, which was abolished with PI3Kγ inact suggesting dephosphorylation of β 1 ARs. Inhibition of PP2A by okadaic acid or Fostriecin resulted in complete loss of β 1 AR resensitization despite the presence of PI3Kγ inact showing that PI3K regulates PP2A activity at the β 1 AR complex. Pre-treatment of single stable cells with Wort resulted in significant increase in β 1 AR-associated phosphatase activity following dobutamine (Dob) treatment (Veh, 4131 ± 14; Dob, 3180 ± 111; Dob + Wort, 17123 ± 680 pmoles/mg protein). Consistently, similar results were obtained in vivo using single transgenic (FLAG-β 1 AR, Veh, 87 ± 12; Dob, 61.7 ± 8.3) and double transgenic (FLAG-β 1 AR and PI3Kγ inact , Veh, 93 ± 9; Dob, 118 ± 6) mice. In vivo metabolic labeling, co-immunoprecipitation and in vitro kinase assays showed that inhibitor of PP2A (I2PP2A) protein as a target of PI3K in regulating PP2A activity at the β 1 AR complex. Indeed, siRNA knock down of I2PP2A results in preservation of β 1 AR function by PM receptor resensitization demonstrating a novel role for PI3K in receptor resensitization. This research has received full or partial funding support from the American Heart Association, AHA Great Rivers Affiliate (Delaware, Kentucky, Ohio, Pennsylvania & West Virginia).

scholarly journals B56-Associated Protein Phosphatase 2A Is Required For Survival and Protects from Apoptosis in Drosophila melanogaster

2002 ◽  
Vol 22 (11) ◽  
pp. 3674-3684 ◽  
Author(s):  
Xinghai Li ◽  
Anne Scuderi ◽  
Anthea Letsou ◽  
David M. Virshup
Keyword(s):  
Cell Death ◽  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Specific Protein ◽  
S2 Cells ◽  
Regulatory Subunits ◽  
Pp2a Activity ◽  
Phosphatase 2A

ABSTRACT Protein phosphorylation and specific protein kinases can initiate signal transduction pathways leading to programmed cell death. The specific protein phosphatases regulating apoptosis have been more elusive. Using double-stranded RNA-mediated interference (RNAi), the role of protein phosphatase 2A (PP2A) in cellular signaling was investigated. Knockdown of A or C subunits individually or of combined B subunits led to concurrent loss of nontargeted PP2A subunits, suggesting that PP2A is an obligate heterotrimer in vivo. Global knockdown of PP2A activity or specific loss of redundant B56 regulatory subunits caused cell death with the morphological and biochemical changes characteristic of apoptosis in cultured S2 cells. B56:PP2A-regulated apoptosis required caspases and the upstream regulators dark, reaper, head involution defective, and dp53. In Drosophila embryos, knockdown of B56-regulated PP2A activity resulted in apoptosis and failure of gastrulation, an effect that was blocked by concurrent RNAi of the caspase Drice. B56-regulated PP2A activity appears to be required upstream of dp53 to maintain a critical proapoptotic substrate in a dephosphorylated, inactive state, thereby preventing apoptosis in Drosophila S2 cells.

scholarly journals beta-blocker reverses inhibition of beta-2 adrenergic receptor resensitization by hypoxia

2020 ◽  
Author(s):  
Yu Sun ◽  
Manveen K. Gupta ◽  
Kate Stenson ◽  
Maradumane L. Mohan ◽  
Nicholas Wanner ◽  
...  
Keyword(s):  
Heart Failure ◽  
Protein Phosphatase ◽  
Adrenergic Receptor ◽  
Protein Phosphatase 2A ◽  
Receptor Internalization ◽  
Pp2a Activity ◽  
Phosphatase 2A ◽  
Β Blocker ◽  
Underlying Mechanisms

AbstractIschemia/hypoxia is major underlying cause for heart failure and stroke. Although beta-adrenergic receptor (βAR) is phosphorylated in response to hypoxia, less is known about the underlying mechanisms. Hypoxia results in robust GRK2-mediated β2AR phosphorylation but does not cause receptor internalization. However, hypoxia leads to significant endosomal-β2AR phosphorylation accompanied by inhibition of β2AR-associated protein phosphatase 2A (PP2A) activity impairing resensitization. Phosphoinositide 3-kinase γ (PI3Kγ) impedes resensitization by phosphorylating endogenous inhibitor of protein phosphatase 2A, I2PP2A that inhibits PP2A activity. Hypoxia increased PI3Kγ activity leading to significant phosphorylation of I2PP2A resulting in inhibition of PP2A and consequently resensitization. Surprisingly, β-blocker abrogated hypoxia-mediated β2AR phosphorylation instead of phosphorylation in normoxia. Subjecting mice to hypoxia leads to significant cardiac dysfunction and β2AR phosphorylation showing conservation of non-canonical hypoxia-mediated pathway in vivo. These findings provide mechanistic insights on hypoxia-mediated βAR dysfunction which is rescued by β-blocker and will have significant implications in heart failure and stroke.

Protein Phosphatase 2A Affects the Symptoms of Depressive Rats by Regulating Extracellular Signal-regulated Kinases/Glycogen Synthase Kinase 3β Signaling Pathway

2019 ◽  
Vol 9 (5) ◽  
pp. 592-598
Author(s):  
Guangshan Zheng ◽  
Zhenzhen Chen ◽  
Longjian Huang ◽  
Jianmin Huang ◽  
Yan Li ◽  
...  
Keyword(s):  
Protein Phosphatase ◽  
Common Mental Disorders ◽  
Glycogen Synthase ◽  
Protein Phosphatase 2A ◽  
Antidepressant Drugs ◽  
Morris Water Maze Test ◽  
Model Group ◽  
Expression Levels ◽  
Pp2a Activity ◽  
Phosphatase 2A

As one of the world's more common mental disorders, the incidence of depression has increased yearly, seriously affecting the lives and health of many people. Protein phosphatase 2A (PP2A) is a protein that is enriched in the brain tissue, is the major serine/threonine phosphatase in the central nervous system, and plays a very important role in many aspects of cellular function. To explore the role of PP2A in the pathogenesis of depression in our study, we constructed the depressive disorder model, which involves the exposure of Sprague Dawley rats to chronic unpredictable stress (CUS). The rats with depression were then treated with different concentrations (low, moderate, high) of okadaic acid (OA), and the optimal OA concentration (OOA) for the follow-up study was selected based on PP2A activity. The results showed that the use of higher OA concentrations corresponded with stronger inhibition of PP2A activity. Moreover, the behavioral test performed on the depression model rats showed that OOA group exhibited significant improvements in weight, as well as in their results in the sucrose preference test, open-field test, and Morris water maze test compared to the model group (P < 0.05). Moreover, when compared with the model group, the amounts of NE and 5-HT increased significantly (P < 0.05), and the expression levels of TH, ERK1, AKT1, as well as the phosphorylation of TH, ERK1, AKT1, and GSK-3β, were observed to be increased in the OOA group (P < 0.05). Furthermore, the content of CORT decreased significantly (P < 0.05), and the expression levels of GSK-3β were decreased in the OOA group (P < 0.05). Thus, the potential mechanism of how OA ameliorates depression in model rats may be through the inhibition of PP2A activity, the increase in phosphorylation levels of AKT and GSK-3β, and through the PP2A/AKT/GSK-3β signal pathway; these components may serve as important intracellular targets for antidepressant drugs.

Colony-stimulating factor-1 (CSF-1) receptor-mediated macrophage differentiation in myeloid cells: a role for tyrosine 559-dependent protein phosphatase 2A (PP2A) activity

2001 ◽  
Vol 358 (2) ◽  
pp. 431-436 ◽  
Author(s):  
Kerrie-Ann McMAHON ◽  
Nicholas J. WILSON ◽  
Denese C. MARKS ◽  
Tina L. BEECROFT ◽  
Genevieve A. WHITTY ◽  
...  
Keyword(s):  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Myeloid Cells ◽  
Differentiation Process ◽  
Colony Stimulating Factor ◽  
Macrophage Differentiation ◽  
Pp2a Activity ◽  
Dependent Signal ◽  
Phosphatase 2A ◽  
Stimulating Factor

M1 myeloid cells transfected with the wild-type (WT) colony-stimulating factor-1 (CSF-1) receptor (CSF-1R; M1/WT cells) undergo CSF-1-dependent macrophage differentiation. By mutation studies, we have provided prior evidence that tyrosine 559 in the CSF-1R cytoplasmic domain governs the Src-dependent differentiation pathway. Further components of this pathway were then sought. We report that the extent of CSF-1-mediated tyrosine phosphorylation of protein phosphatase 2A (PP2A), and the associated loss of its activity were reduced in M1 cells transfected with the CSF-1R with a tyrosine-to-phenylalanine mutation at position 559 (M1/559 cells), compared with the corresponding responses in CSF-1-treated M1/WT cells. This evidence for an involvement of a reduction in PP2A activity in the differentiation process was supported by the restoration of the defect in the CSF-1-mediated differentiation of M1/559 cells by the addition of the PP2A inhibitor, okadaic acid. It was also found that the degree of activation of extracellular-signal-regulated kinase (ERK) activities by CSF-1 was reduced in M1/559 cells, suggesting their involvement in the differentiation process. These data suggest that PP2A and ERK form part of the Src-dependent signal-transduction cascade governing CSF-1-mediated macrophage differentiation in M1 cells.

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.

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