Native and latent forms of skeletal muscle phosphorylase phosphatase

Laloux, Monique; Hers, Henri‐Géry

doi:10.1016/0014-5793(79)80620-1

Cited by 24 publications

(8 citation statements)

References 24 publications

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“…2 shows the inactivation of phosphorylase and the activation of glycogen synthase in liver Sephadex filtrates during incubation at 20°C. In control filtrates, and in agreement with previous reports [32,33], the inactivation of phosphorylase, catalyzed by phosphorylase phosphatase, occurred without delay, whereas the activation of glycogen synthase by synthase phosphatase proceeded only after a latency period, which corresponded to the time required for the inactivation of phosphorylase. The prednisolone treatment introduced two major changes in this pattern: firstly, the inactivation of phosphorylase was 1.5-2-fold faster; secondly, the latency that precedes the activation of glycogen synthase was not only shortened, as expected from the faster disappearance of phosphorylase a, but was also much less complete (Fig.…”

Section: Resultssupporting

confidence: 76%

On the mechanism by which glucocorticoids cause the activation of glycogen synthase in mouse and rat livers

Laloux

Stalmans²,

Hers

1983

European Journal of Biochemistry

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The administration of glucocorticoids to mice caused within 3 h an inactivation of glycogen phosphorylase and activation of glycogen synthase in their livers. In a Sephadex filtrate of liver extract, as well as in a purified glycogen fraction obtained from treated mice, but not in the same preparations obtained from control mice, glycogen synthase was activated without previous inactivation of phosphorylase. The initial rate of synthase activation in a Sephadex filtrate was proportional to the rate of glycogen synthesis in vivo in the same animal. When the glycogen fraction was isolated in the presence of soluble starch, it could be separated from phosphorylase, phosphorylase phosphatase and synthase phosphatase. When added to a control Sephadex filtrate, this purified glycogen fraction obtained from prednisolone-treated mice relieved synthase phosphatase from inhibition by phosphorylase a, indicating that it contained a transferable 'deinhibiting factor'. This deinhibiting factor appears to be a protein and was further purified by alkyl-Sepharose or DEAE-cellulose chromatography. Another modification introduced by treatment with prednisolone was that phosphorylase phosphatase was 1.5 -2-fold more active than in the liver of control mice. This property however did not correlate with the rate of glycogen synthesis in uivo. Administration of actinomycin D prevented the expression of the glucocorticoid effects on the rate of glycogen synthesis in uivo and on the protein phosphatases in vitro. The deinhibition of synthase phosphatase was also observed in isolated rat hepatocytes incubated in the presence of glucocorticoids, but in these preparations synthase was not activated.Long et al. [I] have documented the property of glucocorticoids to cause a large deposition of glycogen in the livers of mice and rats in various metabolic states. After the hormonal treatment, there is a more rapid glycogen synthesis from both glucose [2 -41 and gluconeogenic precursors [3,5], accompanied by a decrease in the concentration of the terminal intermediary metabolite, UDP-glucose [4, 6 -91. These results pointed to an activation of glycogen synthase, which was first demonstrated by Hornbrook et al. [lo] and confirmed by other groups [4,9,11 -131. Furthermore, the increased rate of glycogen synthesis caused by the glucocorticoid treatment was proportional to the concentration of glycogen synthase present in its active (a) form [4,12].There is also indication that glucocorticoids impair hepatic glycogenolysis [I 41, apparently by causing an inactivation of phosphorylase [12,15]. However, the latter effect was probably blunted in these studies because of the technical difficulties involved in the handling of the animals [I61 and in the specific assay of phosphorylase a [17].The activation of glycogen synthase in the liver is controlled by the inhibition that phosphorylase aexerts on glycogen synthase phosphatase (for reviews, see [I 8,191). The activation of glycogen synthase by glucose or insulin and, in isolated liver preparations...

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Section: Resultssupporting

confidence: 76%

On the mechanism by which glucocorticoids cause the activation of glycogen synthase in mouse and rat livers

Laloux

Stalmans²,

Hers

1983

European Journal of Biochemistry

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“…This result conflicts with the work of Hers and co-workers [44-461, who reported that phosphorylase phosphatase is insensitive to inhibitor-I and inhibitor-2 in freshly prepared skeletal muscle and liver extracts (and on this basis concluded that protein phosphatase-1 did not exist in these tissues! [46]). This discrepancy is explained by the different dilutions at which the assays were performed.…”

Section: Influence Of Inhibitor-1 and Inhibitor-2 On Protein Phosphatmentioning

confidence: 99%

“…It could also explain the time dependence of the inhibition in concentrated tissue extracts (Table 4) since inhibitors-1 and 2 might not be able to displace the deinhibitor from protein phosphatase-I instantaneously. The finding of Laloux and Hers [46] that phosphorylase phosphatase in concentrated skeletal muscle extracts becomes more susceptible to inhibitor-I and inhibitor-2 after incubation with trypsin could be explained by inactivation of the deinhibitor, which is known to be very susceptible to this proteinase [49]. However, it should be emphasised that the deinhibitor has not yet been detected in either rabbit skeletal muscle or rabbit liver.…”

Section: The Protein Phosphatases That Act On Inhibitor-1 In Skeletalmentioning

confidence: 99%

“…These findings are consistent with the view that inhibitor-I can regulate protein phosphatase-1 in vivo. The physiological significance of the inhibitor proteins has been questioned [46] because of the heat treatment at 90°C used at the first step of their purification [6,23]. However, inhibitor-I is clearly not generated by this procedure, since it has been partially purified from unboiled extracts, and has exactly the same physical properties as the heat-treated protein [21].…”

Section: Regulation Qf Protein Plmphatase-1 Hy Inhibitor Proteimmentioning

confidence: 99%

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The Protein Phosphatases Involved in Cellular Regulation. 6. Measurement of Type-1 and Type-2 Protein Phosphatases in Extracts of Mammalian Tissues; an Assessment of Their Physiological Roles

1983

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Methods were developed for quantifying protein phosphatases-I, 2A, 2B and 2C in cell extracts, and these procedures were exploited to determine their tissue and subcellular distributions. In addition, the contribution of each enzyme to the total protein phosphatase activity in skeletal muscle and liver extracts towards nine proteins involved in the control of glycogen metabolism, glycolysis/gluconeogenesis, fatty acid synthesis and cholesterol synthesis was assessed.Each protein phosphatase was present at significant concentrations in skeletal muscle, heart muscle, liver, brain and adipose tissue, although the relative amounts differed considerably. In skeletal muscle, protein phosphatase-I was the major enzyme acting on phosphorylase, glycogen synthase and phosphorylase kinase (B-subunit), and thus was the major protein phosphatase responsible for the inactivation of glycogenolysis and stimulation of glycogen synthesis. This idea was reinforced by the observation that 50 ' %, of the protein phosphatase-I activity was associated with the protein-glycogen complex.In the liver, protein phosphatases-1, 2A and 2C each appear to play a role in the regulation of glycogen metabolism. Protein phosphatase-I accounted for a significant fraction of the total potential activity towards phosphorylase and glycogen synthase, and was the major phosphorylase kinase ([hubunit) phosphatase of this tissue. In addition, it was the only protein phosphatase present in the protein-glycogen complex. Protein phosphatase 2A was also a major phosphorylase phosphatase and glycogen synthase phosphatase in this tissue. Protein phosphatase 2C was a significant glycogen synthase phosphatase in the liver, but had negligible activity toward phosphorylase or phosphorylase kinase (p-subunit).In the absence of Ca2+, protein phosphatase 2A was the major phosphorylase kinase (a-subunit) phosphatase and the only inhibitor-1 phosphatase, in skeletal muscle or liver. In the presence of Ca2+, protein phosphatase 2B accounted for most of the activity towards these substrates.Protein phosphatase 2A was the major enzyme acting on L-pyruvate kinase, ATP-citrate lyase and acetyl-CoA carboxylase in rat liver, suggesting an important role in the regulation of glycolysis/gluconeogenesis and fatty acid synthesis. Protein phosphatase 2C was the major enzyme acting on hydroxymethylglutaryl-CoA (HMG-CoA) reductase and HMG-CoA reductase kinase, suggesting an important role in the regulation of cholesterol synthesis. However, the observation that 20% of the protein phosphatase-I in liver was associated with the microsomal fraction suggests that this enzyme may also be involved in regulating HMG-CoA reductase, which is tightly associated with microsomes.The activity of protein phosphatase-I in dilute skeletal muscle and liver extracts was just as sensitive to inhibitor-I and inhibitor-2 as the purified enzyme. In concentrated extracts, higher concentrations of the inhibitor proteins were required and the inhibition was time-dependent. The results explain previous report...

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“…Nimmo and Cohen (12) claim that 90% of the muscle phosphorylase phosphatase and phosphorylase b kinase phosphatase activity is catalyzed by protein phosphatase 1. Laloux and Hers (18), however, claim that the multifunctional protein phosphatase 1 is not present in fresh muscle extracts but is probably produced by proteolysis during an early step in the purification procedure. They conclude that the multifunctional protein phosphatase and the heat-stable inhibitors probably play no physiological role in glycogen metabolism.…”

Section: Discussionmentioning

confidence: 99%

Adrenal glucocorticoid permissive regulation of muscle glycogenolysis: action on protein phosphatase(s) and its inhibitor(s).

Green¹,

Chenoweth²,

Dunn³

1980

Proc. Natl. Acad. Sci. U.S.A.

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Adrenal glucocorticoids exert a permissive action on the glycogen phosphorylase cascade. Epinephrine activation of muscle phosphorylase and phosphorylase b kinase is depressed in adrenalectomized rats. Phosphorylase phosphatase activity is increased by steroid lack, and normal epinephrine inhibition of the enzyme does not occur. Phosphorylase b kinase phosphatase activity is also increased; epineplrine, however, does not inhibit activity in muscle from normal or adrenalectomized rats. Protein phosphatase inhibitor activity is depressed in boiled dialyzed preparations made from adrenalectomized rat muscle. Cortisol replacement therapy restores protein phosphatase inhibitor activity, decreases increased protein phosphatase activity, and restores normal epinephrine-induced activation of phosphorylase b kinase and phosphorylase and epinephrine inhi ition of phosphorylase phosphatase.Although it is well established that adrenal glucocorticoids are required for epinephrine activation of the phosphorylase system in liver (1), skeletal muscle (2), and heart (3), neither the site nor the mechanism of this permissive action is known. Administration of either epinephrine or cyclic AMP to adrenalectomized rats does not result in normal conversion of phosphorylase b to the a form (2). Epinephrine-induced cyclic AMP accumulation is not diminished in perfused hearts from adrenalectomized and gonadectomized rats (3). Basal protein kinase levels are normal and cyclic AMP activation of the enzyme is unimpaired in hearts from adrenalectomized rats (3, 4). All these findings localize the adrenal steroid regulatory action at the levels of phosphorylase, phosphorylase b kinase, the protein phosphatase(s), or the protein phosphatase inhibitor(s).The experiments presented here demonstrate that, in adrenalectomized rats: (a) muscle phosphorylase b kinase activity is significantly decreased; (b) phosphorylase phosphatase and phosphorylase b kinase phosphatase activities are increased; (c) phosphorylase phosphatase inhibitor activity of boiled dialyzed muscle supernatants is depressed; and (d) cortisol replacement reverses all these effects. MATERIALS AND METHODSAnimal Treatment and Maintenance. Experiments were performed on fed male Sprague-Dawley rats obtained from Simonsen Laboratories (Gilroy, CA). Bilateral adrenalectomy was performed under ether anesthesia by the dorsal approach of D'Amour et al. (5) 2 weeks before experimental use. Adrenalectomized rats were given 0.9% NaCl to drink. Both normal and adrenalectomized animals were housed in a vivarium under constant temperature (25 + 1°C) and a 12-hr light/dark cycle and were fed Purina Lab Chow ad lib.The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U. S. C. §1734 solely to indicate this fact. 5711Cortisol Replacement. Cortisol (suspension of the acetate, Towne) was diluted in 0.9% NaCl and administered intraperitoneally to adrenalectomized rats twice daily (...

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Native and latent forms of skeletal muscle phosphorylase phosphatase

Cited by 24 publications

References 24 publications

On the mechanism by which glucocorticoids cause the activation of glycogen synthase in mouse and rat livers

On the mechanism by which glucocorticoids cause the activation of glycogen synthase in mouse and rat livers

The Protein Phosphatases Involved in Cellular Regulation. 6. Measurement of Type-1 and Type-2 Protein Phosphatases in Extracts of Mammalian Tissues; an Assessment of Their Physiological Roles

Adrenal glucocorticoid permissive regulation of muscle glycogenolysis: action on protein phosphatase(s) and its inhibitor(s).

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