Wortmannin inhibits insulin-stimulated activation of protein phosphatase 1 in rat cardiomyocytes

1999 ◽  
Vol 276 (5) ◽  
pp. H1520-H1526 ◽  
Author(s):  
Jane P. de Luca ◽  
Alice K. Garnache ◽  
Jill Rulfs ◽  
Thomas B. Miller
Keyword(s):  
Protein Phosphatase ◽  
Glycogen Synthase ◽  
Protein Phosphatase 1 ◽  
Rat Cardiomyocytes ◽  
Major Function ◽  
Pi3k Inhibitors ◽  
Protein Levels ◽  
Pi3k Activity ◽  
Insulin Dependent ◽  
Phosphatase Activation

A major function of insulin in target tissues is the activation of glycogen synthase. Phosphatidylinositol 3-kinase (PI3K) has been implicated in the insulin-induced activation of glycogen synthase, although the true function of this enzyme remains unclear. Data presented here demonstrate that the PI3K inhibitors wortmannin and LY-294002 block the insulin-stimulated activation of protein phosphatase 1 (PP1) in rat ventricular cardiomyocytes. This loss of phosphatase activation mimics that seen in diabetic cardiomyocytes, in which insulin stimulation fails to activate both PP1 and glycogen synthase. Interestingly, in diabetic cells, insulin stimulated PI3K activity to 300% of that in untreated controls, whereas this activity was increased by only 77% in normal cells. PI3K protein levels, however, were similar in normal and diabetic cells. Our results indicate that PI3K is involved in the stimulation of glycogen synthase activity by insulin through the regulation of PP1. The inability of insulin to stimulate phosphatase activity in diabetic cells, despite a significant increase in PI3K activity, suggests a defect in the insulin signaling pathway that contributes to the pathology of insulin-dependent diabetes.

The level of the glycogen targetting regulatory subunit R5 of protein phosphatase 1 is decreased in the livers of insulin-dependent diabetic rats and starved rats

2001 ◽  
Vol 360 (2) ◽  
pp. 449-459 ◽  
Author(s):  
Gareth J. BROWNE ◽  
Mirela DELIBEGOVIC ◽  
Stefaan KEPPENS ◽  
Willy STALMANS ◽  
Patricia T. W. COHEN
Keyword(s):  
Phosphatase Activity ◽  
Protein Phosphatase ◽  
Glycogen Synthase ◽  
Glycogen Synthesis ◽  
Diabetic Rats ◽  
Protein Phosphatase 1 ◽  
Regulatory Subunit ◽  
Hepatic Glycogen ◽  
Insulin Dependent ◽  
Insulin Dependent Diabetic

Hepatic glycogen synthesis is impaired in insulin-dependent diabetic rats owing to defective activation of glycogen synthase by glycogen-bound protein phosphatase 1 (PP1). The identification of three glycogen-targetting subunits in liver, GL, R5/PTG and R6, which form complexes with the catalytic subunit of PP1 (PP1c), raises the question of whether some or all of these PP1c complexes are subject to regulation by insulin. In liver lysates of control rats, R5 and R6 complexes with PP1c were found to contribute significantly (16 and 21% respectively) to the phosphorylase phosphatase activity associated with the glycogen-targetting subunits, GL–PP1c accounting for the remainder (63%). In liver lysates of insulin-dependent diabetic and of starved rats, the phosphorylase phosphatase activities of the R5 and GL complexes with PP1c were shown by specific immunoadsorption assays to be substantially decreased, and the levels of R5 and GL were shown by immunoblotting to be much lower than those in control extracts. The phosphorylase phosphatase activity of R6–PP1c and the concentration of R6 protein were unaffected by these treatments. Insulin administration to diabetic rats restored the levels of R5 and GL and their associated activities. The regulation of R5 protein levels by insulin was shown to correspond to changes in the level of the mRNA, as has been found for GL. The in vitro glycogen synthase phosphatase/phosphorylase phosphatase activity ratio of R5-PP1c was lower than that of GL–PP1c, suggesting that R5–PP1c may function as a hepatic phosphorylase phosphatase, whereas GL–PP1c may be the major hepatic glycogen synthase phosphatase. In hepatic lysates, more than half the R6 was present in the glycogen-free supernatant, suggesting that R6 may have lower affinity for glycogen than R5 and GL

scholarly journals Loss of the hepatic glycogen-binding subunit (GL) of protein phosphatase 1 underlies deficient glycogen synthesis in insulin-dependent diabetic rats and in adrenalectomized starved rats

1998 ◽  
Vol 333 (2) ◽  
pp. 253-257 ◽  
Author(s):  
Martin J. DOHERTY ◽  
Joan CADEFAU ◽  
Willy STALMANS ◽  
Mathieu BOLLEN ◽  
Patricia T. W. COHEN
Keyword(s):  
Protein Phosphatase ◽  
Glycogen Synthase ◽  
Glycogen Synthesis ◽  
Diabetic Rats ◽  
Catalytic Subunit ◽  
Protein Phosphatase 1 ◽  
Hepatic Glycogen ◽  
Insulin Dependent ◽  
Insulin Dependent Diabetic ◽  
Binding Subunit

Hepatic glycogen synthesis is impaired in insulin-dependent diabetic rats and in adrenalectomized starved rats, and although this is known to be due to defective activation of glycogen synthase by glycogen synthase phosphatase, the underlying molecular mechanism has not been delineated. Glycogen synthase phosphatase comprises the catalytic subunit of protein phosphatase 1 (PP1) complexed with the hepatic glycogen-binding subunit, termed GL. In liver extracts of insulin-dependent diabetic and adrenalectomized starved rats, the level of GL was shown by immunoblotting to be substantially reduced compared with that in control extracts, whereas the level of PP1 catalytic subunit was not affected by these treatments. Insulin administration to diabetic rats restored the level of GL and prolonged administration raised it above the control levels, whereas re-feeding partially restored the GL level in adrenalectomized starved rats. The regulation of GL protein levels by insulin and starvation/feeding was shown to correlate with changes in the level of the GL mRNA, indicating that the long-term regulation of the hepatic glycogen-associated form of PP1 by insulin, and hence the activity of hepatic glycogen synthase, is predominantly mediated through changes in the level of the GL mRNA.

Regulation of glycogen synthase and protein phosphatase-1 by hexosamines

Diabetes ◽  
1996 ◽  
Vol 45 (3) ◽  
pp. 322-327 ◽  
Author(s):  
E. D. Crook ◽  
D. A. McClain
Keyword(s):  
Protein Phosphatase ◽  
Glycogen Synthase ◽  
Protein Phosphatase 1

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.

scholarly journals N-Acetyl-β-D-glucopyranosylamine 6-phosphate is a specific inhibitor of glycogen-bound protein phosphatase 1

1997 ◽  
Vol 328 (2) ◽  
pp. 695-700 ◽  
Author(s):  
Mary BOARD
Keyword(s):  
Phosphatase Activity ◽  
Protein Phosphatase ◽  
Glycogen Phosphorylase ◽  
Glycogen Synthase ◽  
Specific Inhibitor ◽  
Competitive Inhibitor ◽  
Protein Phosphatase 1 ◽  
P Concentration ◽  
Glucose Analogue ◽  
Stimulation Of

Previous work has shown that the C-1-substituted glucose-analogue N-acetyl-β-D-glucopyranosylamine (1-GlcNAc) is a competitive inhibitor of glycogen phosphorylase (GP) and stimulates the inactivation of this enzyme by GP phosphatase. In addition to its effects on GP, 1-GlcNAc also prevents the glucose-led activation of glycogen synthase (GS) in whole hepatocytes. Such an effect on GS was thought to be due to the formation of 1-GlcNAc-6-P by the action of glucokinase within the hepatocyte [Board, Bollen, Stalmans, Kim, Fleet and Johnson (1995) Biochem. J. 311, 845-852]. To investigate this possibility further, a pure preparation of 1-GlcNAc-6-P was synthesized. The effects of the phosphorylated glucose analogue on the activity of protein phosphatase 1 (PP1), the enzyme responsible for dephosphorylation and activation of GS, are reported. During the present study, 1-GlcNAc-6-P inhibited the activity of the glycogen-bound form of PP1, affecting both the GSb phosphatase and GPa phosphatase activities. A level of 50% inhibition of GSb phosphatase activity was achieved with 85 μM 1-GlcNAc-6-P in the absence of Glc-6-P and with 135 μM in the presence of 10 mM Glc-6-P. At either Glc-6-P concentration, 500 μM 1-GlcNAc-6-P completely inhibited activity. The Glc-6-P stimulation of the GPa phosphatase activity of PP1 was negated by 1-GlcNAc-6-P but there was no inhibition of the basal rate in the absence of Glc-6-P. 1-GlcNAc-6-P inhibition was specific for the glycogen-bound form of PP1 and did not inhibit the GSb phosphatase activity of the cytosolic form of the enzyme. The present work explains our previous observations on the inactivating effects on GS of incubating whole hepatocytes with 1-GlcNAc. These observations have their basis in the inhibition of glycogen-bound PP1 by 1-GlcNAc-6-P. A novel inhibitor of PP1, specific for the glycogen-bound form of the enzyme, is presented.

scholarly journals Inhibition of protein phosphatase 1 reverses alcohol-induced ciliary dysfunction

2015 ◽  
Vol 308 (6) ◽  
pp. L577-L585 ◽  
Author(s):  
Michael E. Price ◽  
Jacqueline A. Pavlik ◽  
Joseph H. Sisson ◽  
Todd A. Wyatt
Keyword(s):  
Protein Phosphatase ◽  
Mucociliary Clearance ◽  
Specific Inhibitor ◽  
Alcohol Exposure ◽  
Inhibitory Effect ◽  
Regulatory Proteins ◽  
Protein Phosphatase 1 ◽  
Tissue Cell ◽  
Inhaled Particles ◽  
Phosphatase Activation

Airway mucociliary clearance is a first-line defense of the lung against inhaled particles and debris. Among individuals with alcohol use disorders, there is an increase in lung diseases. We previously identified that prolonged alcohol exposure impairs mucociliary clearance, known as alcohol-induced ciliary dysfunction (AICD). Cilia-localized enzymes, known as the ciliary metabolon, are key to the pathogenesis of AICD. In AICD, cyclic nucleotide-dependent ciliary kinases, which modulate phosphorylation to regulate cilia beat, are desensitized. We hypothesized that alcohol activates cilia-associated protein phosphatase 1 (PP1) activity, driving phosphorylation changes of cilia motility regulatory proteins. To test this hypothesis we identified the effects of prolonged alcohol exposure on phosphatase activity, cilia beat, and kinase responsiveness and cilia-associated phosphorylation targets when stimulated by β-agonist or cAMP. Prolonged alcohol activated PP1 and blocked cAMP-dependent cilia beat and protein kinase A (PKA) responsiveness and phosphorylation of a 29-kDa substrate of PKA. Importantly, prolonged alcohol-induced phosphatase activation was inhibited by the PP1 specific inhibitor, inhibitor-2 (I-2), restoring cAMP-stimulated cilia beat and PKA responsiveness and phosphorylation of the 29-kDa substrate. The I-2 inhibitory effect persisted in tissue, cell, and isolated cilia-organelle models, highlighting the association of ciliary metabolon-localized enzymes to AICD. Prolonged alcohol exposure drives ciliary metabolon-localized PP1 activation. PP1 activation modifies phosphorylation of a 29-kDa protein related to PKA activity. These data reinforce our previous findings that alcohol is acting at the level of the ciliary metabolon to cause ciliary dysfunction and identifies PP1 as a therapeutic target to prevent or reverse AICD.

scholarly journals Lycopene Inhibits Urotensin-II-Induced Cardiomyocyte Hypertrophy in Neonatal Rat Cardiomyocytes

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Hung-Hsing Chao ◽  
Li-Chin Sung ◽  
Cheng-Hsien Chen ◽  
Ju-Chi Liu ◽  
Jin-Jer Chen ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Glycogen Synthase ◽  
Activity Level ◽  
Neonatal Rat ◽  
Cardiomyocyte Hypertrophy ◽  
Urotensin Ii ◽  
Rat Cardiomyocytes ◽  
Protein Levels ◽  
Neonatal Rat Cardiomyocytes ◽  
Tensin Homolog

This study investigated how lycopene affected urotensin-II- (U-II-) induced cardiomyocyte hypertrophy and the possible implicated mechanisms. Neonatal rat cardiomyocytes were exposed to U-II (1 nM) either exclusively or following 6 h of lycopene pretreatment (1–10 μM). The lycopene (3–10 μM) pretreatment significantly inhibited the U-II-induced cardiomyocyte hypertrophy, decreased the production of U-II-induced reactive oxygen species (ROS), and reduced the level of NAD(P)H oxidase-4 expression. Lycopene further inhibited the U-II-induced phosphorylation of the redox-sensitive extracellular signal-regulated kinases. Moreover, lycopene treatment prevented the increase in the phosphorylation of serine-threonine kinase Akt and glycogen synthase kinase-3beta (GSK-3β) caused by U-II without affecting the protein levels of the phosphatase and tensin homolog deleted on chromosome 10 (PTEN). However, lycopene increased the PTEN activity level, suggesting that lycopene prevents ROS-induced PTEN inactivation. These findings imply that lycopene yields antihypertrophic effects that can prevent the activation of the Akt/GSK-3βhypertrophic pathway by modulating PTEN inactivation through U-II treatment. Thus, the data indicate that lycopene prevented U-II-induced cardiomyocyte hypertrophy through a mechanism involving the inhibition of redox signaling. These findings provide novel data regarding the molecular mechanisms by which lycopene regulates cardiomyocyte hypertrophy.

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