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- Aronson, D., et al.
(author)
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Extracellular-regulated protein kinase cascades are activated in response to injury in human skeletal muscle
- 1998
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In: American Journal of Physiology. - : HighWire Press. - 0002-9513 .- 2163-5773. ; 275:2, s. C555-C561
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Journal article (peer-reviewed)abstract
- The mitogen-activated protein (MAP) kinase signaling pathways are believed to act as critical signal transducers between stress stimuli and transcriptional responses in mammalian cells. However, it is not known whether these signaling cascades also participate in the response to injury in human tissues. To determine whether injury to the vastus lateralis muscle activates MAP kinase signaling in human subjects, two needle biopsies or open muscle biopsies were taken from the same incision site 30-60 min apart. The muscle biopsy procedures resulted in striking increases in dual phosphorylation of the extracellular-regulated kinases (ERK1 and ERK2) and in activity of the downstream substrate, the p90 ribosomal S6 kinase. Raf-1 kinase and MAP kinase kinase, upstream activators of ERK, were also markedly stimulated in all subjects. In addition, c-Jun NH2-terminal kinase and p38 kinase, components of two parallel MAP kinase pathways, were activated following muscle injury. The stimulation of the three MAP kinase cascades was present only in the immediate vicinity of the injury, a finding consistent with a local rather than systemic activation of these signaling cascades in response to injury. These data demonstrate that muscle injury induces the stimulation of the three MAP kinase cascades in human skeletal muscle, suggesting a physiological relevance of these protein kinases in the immediate response to tissue injury and possibly in the initiation of wound healing.
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- Balagopal, P., et al.
(author)
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Skeletal muscle heavy-chain synthesis rate in healthy humans
- 1997
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In: American Journal of Physiology. - : HighWire Press. - 0002-9513 .- 2163-5773. ; 272:1, s. 45-50
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Journal article (peer-reviewed)abstract
- Mixed muscle protein synthetic rate has been measured in humans. These measurements represent the average of synthetic rates of all muscle proteins with variable rates. We determined to what extent the synthesis rate of mixed muscle protein in humans reflects that of myosin heavy chain (MHC), the main contractile protein responsible for the conversion of ATP to mechanical energy as muscle contraction. Fractional synthetic rates of MHC and mixed muscle protein were measured from the increment of [C-13]leucine in these proteins in vastus lateralis biopsy samples taken at 5 and 10 h during a primed continuous infusion of L-[1-C-13]leucine in 10 young healthy subjects. Calculations were done by use of plasma [C-13]ketoisocaproate (KIC) and muscle tissue fluid [C-13]leucine as surrogate measures of leucyl-tRNA. Fractional synthetic rate of MHC with plasma KIC (0.0299 +/- 0.0043%/h) and tissue fluid leucine (0.0443 +/- 0.0056%/h) were only 72 +/- 3% of that of mixed muscle protein (0.0408 +/- 0.0032 and 0.0603 +/- 0.0059%/h, respectively, with KIC and tissue fluid leucine). Contribution of MHC (7 +/- 1 mg . kg(-1) . h(-1)) to synthetic rates of whole body mixed muscle protein (36 +/- 5 mg . kg(-1) . h(-1)) and whole body protein (127 +/- 4 mg . kg(-1) . h(-1)) is only 18 +/- 1 and 5 +/- 1%, respectively. This relatively low contribution of MHC to whole body and mixed muscle protein synthesis warrants direct measurement of synthesis rate of MHC in conditions involving abnormalities of muscle contractile function.
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- Barg, Sebastian, et al.
(author)
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Different interactions of cardiac and skeletal muscle ryanodine receptors with FK-506 binding protein isoforms
- 1997
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In: American Journal of Physiology: Cell Physiology. - 1522-1563. ; 272:5 Pt 1, s. C1726-C1733
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Journal article (peer-reviewed)abstract
- In the present study, we compare functional consequences of dissociation and reconstitution of binding proteins FKBP12 and FKBP12.6 with ryanodine receptors from cardiac (RyR2) and skeletal muscle (RyR1). The skeletal muscle RyR1 channel became activated on removal of endogenously bound FKBP12, consistent with previous reports. Both FKBP12 and FKBP12.6 rebind to FKBP-depleted RyR1 and restore its quiescent channel behavior by altering ligand sensitivity, as studied by single-channel recordings in planar lipid bilayers, and macroscopic behavior of the channels (ryanodine binding and net energized Ca2- uptake). By contrast, removal of FKBP12.6 from the cardiac RyR2 did not modulate the function of the channel using the same types of assays as for RyR1. FKBP12 or FKBP12.6 had no effect on channel activity of FKBP12.6-depleted cardiac RyR2, although FKBP12.6 rebinds. Our studies reveal important differences between the two ryanodine receptor isoforms with respect to their functional interaction with FKBP12 and FKBP12.6.
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