Effect of contractile activity on protein turnover in skeletal muscle mitochondrial subfractions

2000 ◽  
Vol 88 (5) ◽  
pp. 1601-1606 ◽  
Author(s):  
Michael K. Connor ◽  
Olga Bezborodova ◽  
C. Patricia Escobar ◽  
David A. Hood
Keyword(s):  
Mitochondrial Biogenesis ◽  
Protein Turnover ◽  
Gastrocnemius Muscle ◽  
Contractile Activity ◽  
Recovery Period ◽  
Chronic Stimulation ◽  
Fast Twitch ◽  
Isolated Rat

To determine the role of intramitochondrial protein synthesis (PS) and degradation (PD) in contractile activity-induced mitochondrial biogenesis, we evaluated rates of [35S]methionine incorporation into protein in isolated rat muscle subsarcolemmal (SS) and intermyofibrillar (IMF) mitochondria. Rates of PS ranged from 47 to 125% greater ( P < 0.05) in IMF compared with SS mitochondria. Intense, acute in situ contractile activity (10 Hz, 5 min) of fast-twitch gastrocnemius muscle resulted in a 50% decrease in PS ( P < 0.05) in SS but not IMF mitochondria. Recovery, or continued contractile activity (55 min), reestablished PS in SS mitochondria. In contrast, PS was not affected in either SS or IMF mitochondria after prolonged (60-min) contractile activity in the presence or absence of a recovery period. PD was not influenced by 5 min of contractile activity in the presence or absence of recovery but was reduced after 60 min of contractions followed by recovery. Chronic stimulation (10 Hz, 3 h/day, 14 days) increased muscle cytochrome- c oxidase activity by 2.2-fold but reduced PS in IMF mitochondria by 29% ( P < 0.05; n = 4). PS in SS mitochondria and PD in both subfractions were not changed by chronic stimulation. Thus acute contractile activity exerts differential effects on protein turnover in IMF and SS mitochondria, and it appears that intramitochondrial PS does not limit the extent of chronic contractile activity-induced mitochondrial biogenesis.

Invited Review: Contractile activity-induced mitochondrial biogenesis in skeletal muscle

2001 ◽  
Vol 90 (3) ◽  
pp. 1137-1157 ◽  
Author(s):  
David A. Hood
Keyword(s):  
Transcription Factors ◽  
Respiratory Chain ◽  
Mitochondrial Biogenesis ◽  
Adenine Nucleotide ◽  
Contractile Activity ◽  
Recovery Period ◽  
Atp Synthesis ◽  
Nucleotide Metabolism ◽  
Significant Shift ◽  
Mrna Levels

Chronic contractile activity produces mitochondrial biogenesis in muscle. This adaptation results in a significant shift in adenine nucleotide metabolism, with attendant improvements in fatigue resistance. The vast majority of mitochondrial proteins are derived from the nuclear genome, necessitating the transcription of genes, the translation of mRNA into protein, the targeting of the protein to a mitochondrial compartment via the import machinery, and the assembly of multisubunit enzyme complexes in the respiratory chain or matrix. Putative signals involved in initiating this pathway of gene expression in response to contractile activity likely arise from combinations of accelerations in ATP turnover or imbalances between mitochondrial ATP synthesis and cellular ATP demand, and Ca2+ fluxes. These rapid events are followed by the activation of exercise-responsive kinases, which phosphorylate proteins such as transcription factors, which subsequently bind to upstream regulatory regions in DNA, to alter transcription rates. Contractile activity increases the mRNA levels of nuclear-encoded proteins such as cytochrome c and mitochondrial transcription factor A (Tfam) and mRNA levels of upstream transcription factors like c- junand nuclear respiratory factor-1 (NRF-1). mRNA level changes are often most evident during the postexercise recovery period, and they can occur as a result of contractile activity-induced increases in transcription or mRNA stability. Tfam is imported into mitochondria and controls the expression of mitochondrial DNA (mtDNA). mtDNA contributes only 13 protein products to the respiratory chain, but they are vital for electron transport and ATP synthesis. Contractile activity increases Tfam expression and accelerates its import into mitochondria, resulting in increased mtDNA transcription and replication. The result of this coordinated expression of the nuclear and the mitochondrial genomes, along with poorly understood changes in phospholipid synthesis, is an expansion of the muscle mitochondrial reticulum. Further understanding of 1) regulation of mtDNA expression, 2) upstream activators of NRF-1 and other transcription factors, 3) the identity of mRNA stabilizing proteins, and 4) potential of contractile activity-induced changes in apoptotic signals are warranted.

Phosphagen and intracellular pH changes during contraction of creatine-depleted rat muscle

1986 ◽  
Vol 250 (2) ◽  
pp. C264-C274 ◽  
Author(s):  
R. A. Meyer ◽  
T. R. Brown ◽  
B. L. Krilowicz ◽  
M. J. Kushmerick
Keyword(s):  
Steady State ◽  
Intracellular Ph ◽  
Muscle Metabolism ◽  
Surface Coil ◽  
The Difference ◽  
Transfer Method ◽  
Fast Twitch ◽  
Resting Muscle

To evaluate the functional role of phosphocreatine (PCr) and creatine in muscle metabolism, these compounds were depleted by feeding rats the creatine analogue, beta-guanidinopropionate (beta-GPA, 2% of diet). Changes in phosphate metabolites and intracellular pH were monitored in gastrocnemius muscle in situ by phosphorus nuclear magnetic resonance (31P-NMR) at 162 MHz using the surface coil technique. After 3 mo of feeding, 25 mumol/g of phosphorylated beta-GPA (beta-GPAP) had accumulated, and PCr, creatine, and ATP levels were reduced to 6, 17, and 56%, respectively, compared with muscles of control animals. In resting muscle, there was no measurable exchange of phosphate between beta-GPAP and ATP by the NMR saturation transfer method. During muscle stimulation at 1 and 5 Hz, the maximum net rate of beta-GPAP hydrolysis was 10% that of PCr in control muscles, so that after 150 s inorganic phosphate had increased to less than 50% of the level attained in control muscles. At both rates, peak twitch force declined toward a steady state more rapidly in beta-GPA-loaded muscles, but after 100 s force was either not different (1 Hz) or significantly greater (5 Hz) in the beta-GPA-fed animals. Intracellular pH initially decreased more rapidly during stimulation and recovered more rapidly afterward in the beta-GPA-loaded muscles compared with controls. This difference could be explained by the difference in expected proton consumption due to net PCr hydrolysis. However, despite buffering by PCr hydrolysis, pH ultimately decreased more in control muscle (6.1 vs. 6.3 for 5 Hz), indicating greater acid accumulation compared with beta-GPA-loaded muscles. In the superficial, predominantly fast-twitch glycolytic section of muscles clamp-frozen after 5-Hz stimulation for 150 s, lactate accumulation was twofold greater in controls. The results indicate that PCr is not essential for steady-state energy production but that the phosphate from PCr hydrolysis may be important for maximum activation of glycogenolysis and/or glycolysis.

scholarly journals Patterns of sarcomere activation, temperature dependence, and effect of ryanodine in chemically skinned cardiac fibers.

1986 ◽  
Vol 87 (6) ◽  
pp. 885-905 ◽  
Author(s):  
A Lundblad ◽  
H Gonzalez-Serratos ◽  
G Inesi ◽  
J Swanson ◽  
P Paolini
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Temperature Dependence ◽  
Calcium Release ◽  
Contractile Activity ◽  
The Other ◽  
Calcium Blockers ◽  
Calcium Accumulation ◽  
Contractile Activation

Functionally skinned and electrochemically shunted myocytes were prepared by perfusing rat hearts with collagenase in order to obtain a technically improved measurement of sarcomere dynamics and to evaluate the role of sarcoplasmic reticulum in situ with respect to contractile activation. In the presence of micromolar calcium, the myocytes exhibited phasic and propagated contraction waves beginning at one end and proceeding along the myocyte. Beating rates, the propagation velocity of the activation wave, and single sarcomere shortening and relaxation velocities were obtained by manual or automated analysis of 16-mm film recorded at 170 frames/s from a camera attached to a microscope that was equipped with a temperature-controlled stage. In parallel experiments, calcium accumulation by the sarcoplasmic reticulum of the myocytes in situ was measured by direct isotopic tracer methods. The frequency (10-38 min-1) of spontaneous contractions, the velocity (1.9-7.4 microns . s-1) of sarcomere shortening, and the velocity (1.7-6.8 microns . s-1) of sarcomere relaxation displayed identical temperature dependences (Q10 = 2.2), which are similar to that of the calcium pump of sarcoplasmic reticulum and are consistent with a rate limit imposed by enzyme-catalyzed mechanisms on all these parameters. On the other hand, the velocity (77-159 microns . s-1) of sequential sarcomere activation displayed a lower temperature dependence (Q10 = 1.5), which is consistent with a diffusion-limited and self-propagating release of calcium from one sarcomere to the other. The phasic contractile activity of the dissociated myocytes was inhibited by 10(-8)-10(6) M ryanodine (and not by myolemmal calcium blockers) under conditions in which calcium accumulation by sarcoplasmic reticulum in situ was demonstrated to proceed optimally. The effect of ryanodine is attributed to an interaction of this drug with sarcotubular structures, producing inhibition of calcium release from the sarcoplasmic reticulum. The consequent lack of sarcomere activation underlines the role of sarcoplasmic reticulum uptake and release in the phasic contractile activation of the electrochemically shunted myocytes.

In vivo IIX and IIB fiber recruitment in gastrocnemius muscle of the rat is compartment related

1996 ◽  
Vol 81 (2) ◽  
pp. 933-942 ◽  
Author(s):  
C. J. De Ruiter ◽  
P. E. Habets ◽  
A. de Haan ◽  
A. J. Sargeant
Keyword(s):  
Cross Sections ◽  
Gastrocnemius Muscle ◽  
Periodic Acid ◽  
Medial Gastrocnemius ◽  
Periodic Acid Schiff ◽  
Fast Twitch ◽  
Medial Gastrocnemius Muscle ◽  
Stimulation Of

The purpose of the present study was to investigate to what extent fast-twitch IIX and IIB fiber recruitment was related to the natural existing muscle compartments (subvolumes of muscle innervated by different primary nerve branches) in rat medial gastrocnemius. Three groups (n = 6) of rats trotted on a motor-driven treadmill (20 degrees incline) at different speeds. A fourth group served as controls, and a fifth group received in situ electrical stimulation of all medial gastrocnemius muscle fibers. Postexercise glycogen levels (periodic acid-Schiff staining intensities) were made. Running caused more and in situ stimulation caused less glycogen breakdown in the proximal IIX and IIB fibers compared with the fibers of the same type in the most distal compartment. Furthermore, the boundaries of the most distal compartment could often be recognized in the periodic acid-Schiff-stained cross sections. It was concluded that during running the proximal IIX and IIB fibers were recruited to a greater extent (and at lower treadmill speeds) compared with the distal IIX and IIB fibers, respectively.

Absence of staircase following disuse in rat gastrocnemius muscle

1988 ◽  
Vol 66 (6) ◽  
pp. 707-713 ◽  
Author(s):  
Brian R. MacIntosh ◽  
Marie-Cristine Roberge ◽  
Phillip F. Gardiner
Keyword(s):  
Skeletal Muscles ◽  
Time Course ◽  
Gastrocnemius Muscle ◽  
Repetitive Stimulation ◽  
Muscle Weight ◽  
Twitch Contraction ◽  
Fast Twitch ◽  
Pulse Stimulation ◽  
Stimulation Of

Repetitive stimulation of mammalian fast-twitch skeletal muscles will normally result in a positive staircase response. This phenomenon was investigated in the rat gastrocnemius muscle following a 2-week period of tetrodotoxin-induced disuse. Muscle inactivity was imposed by superfusing tetrodotoxin in saline over the left sciatic nerve via an implanted osmotic pump. In situ isometric contractile responses to double pulse stimulation and repetitive stimulation at 10 Hz were determined the day after removal of the pump. Two weeks of disuse resulted in 40% muscle weight loss. A twitch contraction gave the same force when expressed per gram of wet muscle weight in control muscles, 317 ± 24.6 [Formula: see text] g/g, as compared with tetrodotoxin-treated muscles, 328 ± 24.2 g/g. Both contraction time and half-relaxation time were prolonged following treatment with tetrodotoxin. Repetitive stimulation at 10 Hz resulted in a positive staircase response in the control muscles, but not in muscles of the tetrodotoxin-treated rats. The observed changes in the time course of the twitch contraction with repetitive stimulation following tetrodotoxin-induced disuse are consistent with alterations in sarcoplasmic reticulum handling of calcium. It is not certain if there is a change following disuse in the mechanism normally associated with staircase or if this mechanism is merely opposed by an early fatigue.

Neural Modulation of Gut Motility by Myomodulin Peptides and Acetylcholine in the Snail Lymnaea

1998 ◽  
Vol 79 (5) ◽  
pp. 2460-2474 ◽  
Author(s):  
Stephen J. Perry ◽  
Volko A. Straub ◽  
György Kemenes ◽  
Niovi Santama ◽  
Belinda M. Worster ◽  
...  
Keyword(s):  
Motor Neurons ◽  
Lymnaea Stagnalis ◽  
Contractile Activity ◽  
Gut Motility ◽  
Antibody Staining ◽  
Neural Modulation ◽  
Neuronal Types ◽  
Cell Culture Assay

Perry, Stephen J., Volko A. Straub, György Kemenes, Niovi Santama, Belinda M. Worster, Julian F. Burke, and Paul R. Benjamin. Neural modulation of gut motility by myomodulin peptides and acetylcholine in the snail Lymnaea. J. Neurophysiol. 79: 2460–2474, 1998. Families of peptide neuromodulators are believed to play important roles in neural networks that control behaviors. Here, we investigate the expression and role of one such group of modulators, the myomodulins, in the feeding system of Lymnaea stagnalis. Using a combination of in situ hybridization and antibody staining, expression of the myomodulin gene was confirmed in a number of identified behaviorally significant neuronal types, including the paired B2 motor neurons. The B2 cells were shown to project axons to the proesophagus, where they modulate foregut contractile activity. The presence of the five myomodulin peptide structures was confirmed in the B2 cells, the proesophagus, and the intervening nerve by mass spectrometry. Using a sensitive cell culture assay, evidence that the B2 cells are cholinergic also is presented. Application of four of the five myomodulin peptides to the isolated foregut increased both contraction frequency and tonus, whereas the main effect of acetylcholine (ACh) application was a large tonal contraction. The fifth myomodulin peptide (pQIPMLRLamide) appeared to have little or no effect on gut motility. Coapplication of all five myomodulin peptides gave a greater increase in tonus than that produced by the peptides applied individually, suggesting that corelease of the peptides onto the gut would produce an enhanced response. The combined effects that the myomodulin peptides and ACh have on foregut motility can mimic the main actions of B2 cell stimulation.

Adaptation of rat skeletal muscle to creatine depletion: AMP deaminase and AMP deamination

1992 ◽  
Vol 73 (6) ◽  
pp. 2713-2716 ◽  
Author(s):  
J. M. Ren ◽  
J. O. Holloszy
Keyword(s):  
Skeletal Muscle ◽  
Contractile Activity ◽  
Activity Level ◽  
Amp Deaminase ◽  
Slow Twitch Muscle ◽  
Fast Twitch Muscle ◽  
Slow Twitch ◽  
Fast Twitch ◽  
Similar Decrease

AMP deaminase catalyzes deamination of the AMP formed in contracting muscles to inosine 5′-monophosphate (IMP). Slow-twitch muscle has only approximately 30% as high a level of AMP deaminase activity as fast-twitch muscle in the rat, and rates of IMP formation during intense contractile activity are much lower in slow-twitch muscle. We found that feeding the creatine analogue beta-guanidinopropionic acid (beta-GPA) to rats, which results in creatine depletion, causes a large decrease in muscle AMP deaminase. This adaptation was used to evaluate the role of AMP deaminase activity level in accounting for differences in IMP production in slow-twitch and fast-twitch muscles. beta-GPA feeding for 3 wk lowered AMP deaminase activity in fast-twitch epitrochlearis muscle to a level similar to that found in the normal slow-twitch soleus muscle but had no effect on the magnitude of the increase in IMP in response to intense contractile activity. Despite a similar decrease in ATP in the normal soleus and the epitrochlearis from beta-GPA-fed rats, the increase in IMP was only approximately 30% as great in the soleus in response to intense contractile activity. These results demonstrate that the accumulation of less IMP in slow- compared with fast-twitch skeletal muscle during contractile activity is not due to the lower level of AMP deaminase in slow-twitch muscle.

Regulation of Egr-1, SRF, and Sp1 mRNA expression in contracting skeletal muscle cells

2004 ◽  
Vol 97 (6) ◽  
pp. 2207-2213 ◽  
Author(s):  
Isabella Irrcher ◽  
David A. Hood
Keyword(s):  
Skeletal Muscle ◽  
Transcription Factors ◽  
Mrna Expression ◽  
Mitochondrial Biogenesis ◽  
Contractile Activity ◽  
Recovery Period ◽  
Muscle Cells ◽  
Skeletal Muscle Cells ◽  
Mrna Levels ◽  
Serum Response

The early cellular signals associated with contractile activity initiate the activation and induction of transcription factors that regulate changes in skeletal muscle phenotype. The transcription factors Egr-1, Sp1, and serum response factor (SRF) are potentially important mediators of mitochondrial biogenesis based on the prevalence of binding sites for them in the promoter regions of genes encoding mitochondrial proteins, including PGC-1α, the important regulator of mitochondrial biogenesis. Thus, to further define a role for transcription factors at the onset of contractile activity, we examined the time-dependent alterations in Egr-1, Sp1, and SRF mRNA and the levels in electrically stimulated mouse C2C12 skeletal muscle cells. Early transient increases in Egr-1 mRNA levels within 30 min ( P < 0.05) of contractile activity led to threefold increases ( P < 0.05) in Egr-1 protein by 60 min. The increase in Egr-1 mRNA was not because of increased stability, as Egr-1 mRNA half-life after 30 min of stimulation showed only a 58% decline. Stimulation of muscle cells had no effect on Sp1 mRNA but led to progressive increases ( P < 0.05) in SRF mRNA by 30 and 60 min. This was not matched by increases in SRF protein but occurred coincident with increases ( P < 0.05) in SRF-serum response element DNA binding at 30 and 60 min as a result of SRF phosphorylation on serine-103. To assess the importance of the recovery period, 12 h of continuous contractile activity was compared with four successive 3-h bouts, with an intervening 21-h recovery period after each bout. Continuous contractile activity led to a twofold increase ( P < 0.05) in Egr-1 mRNA, no change in SRF mRNA, and a 43% decrease in Sp1 mRNA expression. The recovery period prevented the decline in Sp1 mRNA, produced a decrease in Egr-1 mRNA, and had no effect on SRF mRNA. Thus continuous and intermittent contractile activity evoked different specific transcription factor expression patterns, which may ultimately contribute to divergent qualitative, or temporal patterns of, phenotypic adaptation in muscle.

scholarly journals Effect of contractile activity on PGC-1α transcription in young and aged skeletal muscle

2018 ◽  
Vol 124 (6) ◽  
pp. 1605-1615 ◽  
Author(s):  
Heather N. Carter ◽  
Marion Pauly ◽  
Liam D. Tryon ◽  
David A. Hood
Keyword(s):  
Skeletal Muscle ◽  
Dna Methylation ◽  
Transcription Factor ◽  
Mitochondrial Biogenesis ◽  
Acute Exercise ◽  
Contractile Activity ◽  
Expression Patterns ◽  
Recovery Period ◽  
Peroxisome Proliferator ◽  
Altered Expression

Mitochondrial impairments are often noted in aged skeletal muscle. The transcriptional coactivator peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) is integral to maintaining mitochondria, and its expression declines in aged muscle. It remains unknown whether this is due to a transcriptional deficit during aging. Our study examined PGC-1α transcription in muscle from young and old F344BN rats. Using a rat PGC-1α promoter-reporter construct, we found that PGC-1α transcription was reduced by ∼65% in aged TA muscle, accompanied by decreases in PGC-1α mRNA and transcript stability. Altered expression patterns in PGC-1α transcription regulatory factors, including nuclear respiratory factor 2, upstream transcription factor 1, activating transcription factor 2, and yin yang 1, were noted in aged muscle. Acute contractile activity (CA) followed by recovery was employed to examine whether PGC-1α transcription could be activated in aged muscle similar to that observed in young muscle. AMPK and p38 signaling was attenuated in aged muscle. CA evoked an upregulation of PGC-1α transcription in both young and aged groups, whereas mRNAs encoding PGC-1α and cytochrome oxidase subunit IV were induced during the recovery period. Global DNA methylation, an inhibitory event for transcription, was enhanced in aged muscle, likely a result of elevated methyltransferase enzyme Dnmt3b in aged muscle. Successive bouts of CA for 7 days to evaluate longer-term consequences resulted in a rescue of PGC-1α and downstream mRNAs in aged muscle. Our data indicate that diminished mitochondria in aged muscle is due partly to a deficit in PGC-1α transcription, a result of attenuated upstream signaling. Contractile activity is an appropriate countermeasure to restore PGC-1α expression and mitochondrial content in aged muscle. NEW & NOTEWORTHY PGC-1α is a regulator of mitochondrial biogenesis in muscle. We demonstrate that PGC-1α expression is reduced in aging muscle due to decreases in transcriptional and posttranscriptional mechanisms. The transcriptional deficit is due to alterations in transcription factor expression, reduced signaling, and DNA methylation. Acute exercise can initiate signaling to reverse the transcriptional defect, restoring PGC-1α expression toward young values, suggesting a mechanism whereby aged muscle can respond to exercise for the promotion of mitochondrial biogenesis.

Glycogen synthesis from lactate in a chronically active muscle

1989 ◽  
Vol 66 (5) ◽  
pp. 2231-2238 ◽  
Author(s):  
R. J. Talmadge ◽  
J. I. Scheide ◽  
H. Silverman
Keyword(s):  
Gastrocnemius Muscle ◽  
Glycogen Synthesis ◽  
Muscle Fibers ◽  
Glycogen Storage ◽  
Normal Muscle ◽  
Body Organ ◽  
Gastrocnemius Muscles ◽  
Fast Twitch ◽  
Whole Muscle

In response to neural overactivity (pseudomyotonia), gastrocnemius muscle fibers from C57Bl/6Jdy2J/dy2J mice have different metabolic profiles compared with normal mice. A population of fibers in the fast-twitch superficial region of the dy2J gastrocnemius stores unusually high amounts of glycogen, leading to an increased glycogen storage in the whole muscle. The dy2J muscle also contains twice as much lactate as normal muscle. A [14C]lactate intraperitoneal injection leads to preferential 14C incorporation into glycogen in the dy2J muscle compared with normal muscle. To determine whether skeletal muscles were incorporating lactate into glycogen without body organ (liver, kidney) input, gastrocnemius muscles were bathed in 10 mM [14C]lactate with intact neural and arterial supply but with impeded venous return. The contralateral gastrocnemius serves as a control for body organ input. By using this in situ procedure, we demonstrate that under conditions of high lactate both normal and dy2J muscle can directly synthesize glycogen from lactate. In this case, normal whole muscle incorporates [14C] lactate into glycogen at a higher rate than dy2J whole muscle. Autoradiography, however, suggests that the high-glycogen-containing muscle fibers in the dy2J muscle incorporate lactate into glycogen at nearly four times the rate of normal or surrounding muscle fibers.

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