Control of Phosphorylase Activity in a Muscle Glycogen Particle

The purpose of this study was to examine the regulation (hormonal, substrate, and allosteric) of muscle glycogen phosphorylase (Phos) activity and glycogenolysis after short-term endurance training. Eight untrained males completed 6 days of cycle exercise (2 h/day) at 65% of maximal O2 uptake (Vo2max). Before and after training subjects cycled for 15 min at 80% of Vo2max, and muscle biopsies and blood samples were obtained at 0 and 30 s, 7.5 and 15 min, and 0, 5, 10, and 15 min of exercise. Vo2max was unchanged with training but citrate synthase (CS) activity increased by 20%. Muscle glycogenolysis was reduced by 42% during the 15-min exercise challenge following training (198.8 +/- 36.9 vs. 115.4 +/- 25.1 mmol/kg dry muscle), and plasma epinephrine was blunted at 15 min of exercise. The Phos a mole fraction was unaffected by training. Muscle phosphocreatine utilization and free Pi and AMP accumulations were reduced with training at 7.5 and 15 min of exercise. It is concluded that posttransformational control of Phos, exerted by reductions in substrate (free Pi) and allosteric modulator (free AMP) contents, is responsible for a blunted muscle glycogenolysis after 6 days of endurance training. The increase in CS activity suggests that the reduction of muscle glycogenolysis was due in part to an enhanced mitochondrial potential.

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Adenovirus-mediated delivery into myocytes of muscle glycogen phosphorylase, the enzyme deficient in patients with glycogen-storage disease type V

Biochemical Journal ◽

10.1042/bj3041009 ◽

1994 ◽

Vol 304 (3) ◽

pp. 1009-1014 ◽

Cited By ~ 12

Author(s):

S Baqué ◽

C B Newgard ◽

R D Gerard ◽

J J Guinovart ◽

A M Gómez-Foix

Keyword(s):

Muscle Glycogen ◽

Glycogen Phosphorylase ◽

Recombinant Adenovirus ◽

Genetic Diseases ◽

C2c12 Myoblast ◽

Mrna Levels ◽

Phosphorylase Activity ◽

Muscle Phosphorylase ◽

The Impact

The feasibility of using adenovirus as a vector for the introduction of glycogen phosphorylase activity into myocytes has been examined. We used the C2C12 myoblast cell line to assay the impact of phosphorylase gene transfer on myocyte glycogen metabolism and to reproduce in vitro the two strategies proposed for the treatment of muscle genetic diseases, myoblast transplantation and direct DNA delivery. In this study, a recombinant adenovirus containing the muscle glycogen phosphorylase cDNA transcribed from the cytomegalovirus promoter (AdCMV-MGP) was used to transduce both differentiating myoblasts and nondividing mature myotube cells. Muscle glycogen phosphorylase mRNA levels and total phosphorylase activity were increased in both cell types after viral treatment although more efficiently in the differentiated myotubes. The increase in phosphorylase activity was transient (15 days) in myoblasts whereas in myotubes higher levels of phosphorylase gene expression and activity were reached, which remained above control levels for the duration of the study (20 days). The introduction of muscle phosphorylase into myotubes enhanced their glycogenolytic capacity. AdCMV MGP-transduced myotubes had lower glycogen levels under basal conditions. In addition, these engineered cells showed more extensive glycogenolysis in response to both adrenaline, which stimulates glycogen phosphorylase phosphorylation, and carbonyl cyanide m-chlorophenylhydrazone, a metabolic uncoupler. In conclusion, transfer of the muscle glycogen phosphorylase cDNA into myotubes confers an enhanced and regulatable glycogenolytic capacity. Thus this system might be useful for delivery of muscle glycogen phosphorylase and restoration of glycogenolysis in muscle cells from patients with muscle phosphorylase deficiency (McArdle's disease).

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Mechanism linking glycogen concentration and glycogenolytic rate in perfused contracting rat skeletal muscle

Biochemical Journal ◽

10.1042/bj2840777 ◽

1992 ◽

Vol 284 (3) ◽

pp. 777-780 ◽

Cited By ~ 46

Author(s):

P Hespel ◽

E A Richter

Keyword(s):

Skeletal Muscle ◽

Muscle Glycogen ◽

Rat Skeletal Muscle ◽

Phosphorylase Activity ◽

Tension Development ◽

Glycogen Concentration ◽

The Difference ◽

Resting Muscle ◽

Muscle Glycogen Concentration ◽

Glycogen Breakdown

The influence of differences in glycogen concentration on glycogen breakdown and on phosphorylase activity was investigated in perfused contracting rat skeletal muscle. The rats were preconditioned by a combination of swimming exercise and diet (carbohydrate-free or carbohydrate-rich) in order to obtain four sub-groups of rats with varying resting muscle glycogen concentrations (range 10-60 mumol/g wet wt.). Pre-contraction muscle glycogen concentration was closely positively correlated with glycogen breakdown over 15 min of intermittent short tetanic contractions (r = 0.75; P less than 0.001; n = 56) at the same tension development and oxygen uptake. Additional studies in supercompensated and glycogen-depleted hindquarters during electrical stimulation for 20 s or 2 min revealed that the difference in glycogenolytic rate was found at the beginning rather than at the end of the contraction period. Phosphorylase alpha activity was approximately twice as high (P less than 0.001) in supercompensated muscles as in glycogen-depleted muscles after 20 s as well as after 2 min of contractions. It is concluded that glycogen concentration is an important determinant of phosphorylase activity in contracting skeletal muscle, and probably via this mechanism a regulator of glycogenolytic rate during muscle contraction.

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Phosphorylase and glycogen levels in skeletal muscle and liver of hibernating and nonhibernating bats

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1959.197.5.1059 ◽

1959 ◽

Vol 197 (5) ◽

pp. 1059-1062 ◽

Cited By ~ 21

Author(s):

Samuel L. Leonard ◽

William A. Wimsatt

Keyword(s):

Skeletal Muscle ◽

Muscle Glycogen ◽

Liver Glycogen ◽

Myotis Lucifugus ◽

Phosphorylase Activity ◽

Activity Ratios ◽

Muscle Phosphorylase ◽

Wet Weight ◽

Muscle Phosphorylase Activity ◽

Made In

Determinations of skeletal muscle and liver glycogen concentration and active a and total t phosphorylase activities were made in bats ( Myotis lucifugus) hibernating at 3°–5° and 20 hours after arousal at room temperature. After arousal, liver glycogen was decreased by half and muscle glycogen was increased over twofold. Concomitantly, muscle phosphorylase a was increased, phosphorylase t was unchanged and the ratio a/t was increased. In the liver, phosphorylase a, t and the ratios were increased upon arousal (calculated per unit of wet weight and per mg N). Epinephrine treatment was ineffective in the torpid hibernating bats, but in aroused bats, it decreased muscle and liver glycogen but increased muscle phosphorylase activity ratios only slightly. Histamine was ineffective in the aroused bats. Stimulating aroused bats to fly for short periods consistently resulted in lower muscle glycogen levels and in no change in muscle phosphorylase activity ratios. It is concluded that a) at least part of the increased muscle glycogen in the aroused bats comes from the liver, b) the changes in glycogen levels and phosphorylase activity are in some manner related and c) liver phosphorylase changes upon arousal, unlike that in muscle phosphorylase, involves an increase in total enzyme potential.

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Spin-labelled phosphorylase as a probe in a rabbit muscle glycogen particle fraction

FEBS Letters ◽

10.1016/0014-5793(74)80750-7 ◽

1974 ◽

Vol 42 (3) ◽

pp. 296-300 ◽

Cited By ~ 4

Author(s):

S.J.W. Busby ◽

J.R. Griffiths ◽

G.K. Radda

Keyword(s):

Muscle Glycogen ◽

Rabbit Muscle ◽

Particle Fraction ◽

Glycogen Particle

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Regulation of muscle glycogen phosphorylase activity during intense aerobic cycling with elevated FFA

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1996.270.1.e116 ◽

1996 ◽

Vol 270 (1) ◽

pp. E116-E125 ◽

Cited By ~ 19

Author(s):

D. J. Dyck ◽

S. J. Peters ◽

P. S. Wendling ◽

A. Chesley ◽

E. Hultman ◽

...

Keyword(s):

Muscle Glycogen ◽

Glycogen Phosphorylase ◽

O2 Consumption ◽

Elevated Plasma ◽

Phosphorylase Activity ◽

Allosteric Regulator ◽

Plasma Ffa ◽

Glycogen Phosphorylase Activity ◽

Muscle Biopsies ◽

Allosteric Activator

This study examined muscle glycogenolysis and the regulation of glycogen phosphorylase (Phos) activity during 15 min of cycling at 85% of maximal O2 consumption (VO2max) in control and high free fatty acid (FFA; Intralipid-heparin) conditions in 11 subjects. Muscle biopsies were sampled at rest and 1, 5, and 15 min of exercise, and glycogen Phos transformation state (%Phos alpha), substrate (Pi, glycogen), and allosteric regulator (ADP, AMP, IMP) contents were measured. Infusion of intralipid elevated plasma FFA from 0.32 +/- 0.04 mM at rest to 1.00 +/- 0.04 mM just before exercise and 1.12 +/- 0.10 mM at 14 min of exercise. In the control trial, plasma FFA were 0.36 +/- 0.04 mM at rest and unchanged at the end of exercise (0.34 +/- 0.03 mM). Seven subjects used less muscle glycogen (46.7 +/- 7.6%, mean +/- SE) during the Intralipid trial, and four did not respond. In subjects who spared glycogen, glycogen Phos transformation into the active (alpha) form was unaffected by high FFA except for a nonsignificant reduction during the initial 5 min of exercise. Total AMP and IMP contents were not significantly different during exercise between trials, but total ADP was significantly lower with Intralipid only at 15 min. The calculated free ADP, AMP, and Pi contents were lower with Intralipid but not significantly different. However, when the present results were pooled with the data from a previous study using the same protocol [Dyck et al., Am. J. Physiol. 265 (Endocrinol, Metab. 28): E852-E859, 1993], the free ADP, AMP, and Pi contents of all subjects who spared glycogen (n = 13) were significantly lower at 15 min in the Intralipid trial. The findings suggest that the elevation of plasma FFA during intense cycling spares muscle glycogen by posttransformational regulation of Phos. This may be due to blunted increases in the contents of AMP, an allosteric activator of Phos alpha, and Pi, a substrate for Phos.

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