Absence of myosin light chain phosphorylation and twitch potentiation in atrophied skeletal muscle

Tubman, L. Aaron; Rassier, Dilson E.; MacIntosh, Brian R.

doi:10.1139/y96-065

Cited by 20 publications

(15 citation statements)

References 15 publications

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“…R-LC phosphorylation levels for atrophied muscles have not been previously measured following tetanic stimulation using an in situ preparation. These results are in contrast to the observation that low frequency stimulation (10 Hz), which does not result in staircase in atrophied rat gastrocnemius muscles, does not increase the R-LC phosphorylation from resting levels [8].…”

Section: Discussioncontrasting

confidence: 99%

“…The enhancement of R-LC phosphorylation following a tetanic stimulation (B) is evident by the to the attenuation of stimulation induced R-LC phosphorylation. These observations together with the previous findings that severe attenuation of staircase potentiation is associated with a virtual absence of R-LC phosphorylation [8], support the theory that R-LC phosphorylation is the primary mechanism for twitch potentiation. effects of denervation on contractile properties in rat fast-twitch (EDL) muscle fibres at 21°C.…”

Section: Discussionsupporting

confidence: 86%

“…Staircase potentiation is absent in tetrodotoxin (TTX)-induced disuse atrophy [6] and recent experimental data show that this is accompanied by an apparent attenuation of R-LC phosphorylation [8]. This observation is consistent with the theory that R-LC phosphorylation is the mechanism for staircase potentiation.…”

Section: Introductionsupporting

confidence: 82%

“…The procedure utilized was the same as that used in a previous study [8]. Muscle extract was subjected to pyrophosphate polyacrylamide gel electrophoresis to isolate the myosin.…”

Section: Biochemical Analysismentioning

confidence: 99%

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Attenuation of myosin light chain phosphorylation and posttetanic potentiation in atrophied skeletal muscle

1997

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Previously we have demonstrated that the absence of staircase potentiation in atrophied rat gastrocnemius muscle is accompanied by a virtual absence of phosphorylation of the regulatory light chains (R-LC) of myosin. It was our purpose in the present study to determine if posttetanic potentiation and corresponding R-LC phosphorylation were also attenuated in disuse-atrophied muscles. Two weeks after a spinal hemisection (T12), twitch and tetanic contractile characteristics were measured in situ in control, sham-treated and atrophied (hemisected) muscles. Posttetanic potentiation 20 s after a 2 s tetanic contraction (200 Hz) was depressed in atrophied muscles (128.7 +/- 2.6%; mean +/- SEM) when compared to sham-treated (149.9 +/- 2.4%) and control (142.9 +/- 2. 7%) muscles. Atrophied muscles demonstrated a significant increase in R-LC phosphorylation from rest (0.05 +/- 0.04 moles of phosphate/mole of R-LC) to posttetanic conditions (0.21 +/- 0.03 moles of phosphate/mole of R-LC), and less phosphorylation than control and sham-treated muscles (0.43 +/- 0.06 and 0.49 +/- 0.03 moles of phosphate/mole of R-LC, respectively) after tetanic stimulation. The preservation of the potentiation-phosphorylation relationship in atrophied muscles is consistent with the hypothesis that R-LC phosphorylation may be the principal mechanism for twitch potentiation.

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Section: Discussioncontrasting

confidence: 99%

Section: Discussionsupporting

confidence: 86%

Section: Introductionsupporting

confidence: 82%

“…The procedure utilized was the same as that used in a previous study [8]. Muscle extract was subjected to pyrophosphate polyacrylamide gel electrophoresis to isolate the myosin.…”

Section: Biochemical Analysismentioning

confidence: 99%

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Attenuation of myosin light chain phosphorylation and posttetanic potentiation in atrophied skeletal muscle

1997

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“…In addition, a reduced myosin-RLC phosphorylation during the conditioning contractile activity has been observed in atrophied muscles and may have contributed to the diminished PAP in elderly individuals (Tubman et al 1996(Tubman et al , 1997. However, despite the diVerence in absolute PAP Fig.…”

Section: Summation Of the Mechanical Contributions At Various Frequenmentioning

confidence: 97%

Postactivation potentiation of short tetanic contractions is differently influenced by stimulation frequency in young and elderly adults

2008

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The purpose of this study was to examine the effects of postactivation potentiation (PAP) on the torque and rate of torque development for contractions evoked by short trains of stimuli at different frequencies, in young and elderly adults. Individual mechanical contributions to each electrical stimulus within trains were also analysed. Single pulse, and two- (PT2) and three-pulse trains (PT3) delivered at 20, 50, 80 and 100 Hz were evoked before and during a 10 min period after a 6-s conditioning MVC. The results show that PAP of the torque for PT2 decreased with the increase of the stimulation frequency for young (from 184.5 to 140.4% of control values) and elderly (from 140.5 to 109.6%). Regardless of the stimulation frequency, the peak of PAP was greater in young than in elderly and occurred immediately after the conditioning MVC but was delayed for the 100 Hz condition in elderly adults. For PT3, the results were similar although the extent of PAP was less. The PAP of the mechanical contributions within the trains also decreased with the augmentation of the stimulation frequency. For most of the frequencies above 20 Hz, the peak of PAP for each mechanical contribution was delayed by 1 min after the conditioning MVC. These results indicate an age- and frequency-related PAP saturation of the successive mechanical contributions within a train of stimuli that decrease with time. The functional implication of the findings is that PAP effect is lower and delayed at high compared with low activation rate.

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Modulation of Skeletal Muscle Contraction by Myosin Phosphorylation

Vandenboom

2016

Comprehensive Physiology

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The striated muscle sarcomere is a highly organized and complex enzymatic and structural organelle. Evolutionary pressures have played a vital role in determining the structure-function relationship of each protein within the sarcomere. A key part of this multimeric assembly is the light chain-binding domain (LCBD) of the myosin II motor molecule. This elongated "beam" functions as a biological lever, amplifying small interdomain movements within the myosin head into piconewton forces and nanometer displacements against the thin filament during the cross-bridge cycle. The LCBD contains two subunits known as the essential and regulatory myosin light chains (ELC and RLC, respectively). Isoformic differences in these respective species provide molecular diversity and, in addition, sites for phosphorylation of serine residues, a highly conserved feature of striated muscle systems. Work on permeabilized skeletal fibers and thick filament systems shows that the skeletal myosin light chain kinase catalyzed phosphorylation of the RLC alters the "interacting head motif" of myosin motor heads on the thick filament surface, with myriad consequences for muscle biology. At rest, structure-function changes may upregulate actomyosin ATPase activity of phosphorylated cross-bridges. During activation, these same changes may increase the Ca2+ sensitivity of force development to enhance force, work, and power output, outcomes known as "potentiation." Thus, although other mechanisms may contribute, RLC phosphorylation may represent a form of thick filament activation that provides a "molecular memory" of contraction. The clinical significance of these RLC phosphorylation mediated alterations to contractile performance of various striated muscle systems are just beginning to be understood. © 2017 American Physiological Society. Compr Physiol 7:171-212, 2017.

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Absence of myosin light chain phosphorylation and twitch potentiation in atrophied skeletal muscle

Cited by 20 publications

References 15 publications

Attenuation of myosin light chain phosphorylation and posttetanic potentiation in atrophied skeletal muscle

Attenuation of myosin light chain phosphorylation and posttetanic potentiation in atrophied skeletal muscle

Postactivation potentiation of short tetanic contractions is differently influenced by stimulation frequency in young and elderly adults

Modulation of Skeletal Muscle Contraction by Myosin Phosphorylation

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