Acute alterations in sodium flux <i>in vitro</i> lead to decreased myofibrillar protein breakdown in rat skeletal muscle

Goodman, M. N.

doi:10.1042/bj2470151

Cited by 23 publications

(14 citation statements)

References 45 publications

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“…For example, TPA inhibits 3-MH release from EDL muscle in vitro (Goodman, 1987) and from C 2 C 12 myotubes (Thompson et al, 1996). This suggests that the PKC family may play an important role in the regulation of myofibrillar protein degradation (Thompson and Palmer, 1998) and that specific isoforms might represent important targets for intervention therapies in various disease states (Palmer and Thompson, 1999).…”

Section: Discussionmentioning

confidence: 99%

Stimulation of myofibrillar protein degradation and expression of mRNA encoding the ubiquitin-proteasome system in C2C12 myotubes by dexamethasone: effect of the proteasome inhibitor MG-132

Thompson¹,

Thom²,

Partridge³

et al. 1999

J. Cell. Phys.

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Addition of the synthetic glucocorticoid, dexamethasone (Dex) to serum-deprived C(2)C(12) myotubes elicited time- and concentration-dependent changes in N(tau)-methylhistidine (3-MH), a marker of myofibrillar protein degradation. Within 24 h, 100 nM Dex significantly decreased the cell content of 3-MH and increased release into the medium. Both of these responses had increased in magnitude by 48 h and then declined toward basal values by 72 h. The increase in the release of 3-MH closely paralleled its loss from the cell protein. Furthermore, Dex also decreased the 3-MH:total cell protein ratio, suggesting that myofibrillar proteins were being preferentially degraded. Incubation of myotubes with the peptide aldehyde, MG-132, an inhibitor of proteolysis by the (ATP)-ubiquitin (Ub)-dependent proteasome, prevented both the basal release of 3-MH (>95%) and the increased release of 3-MH into the medium in response to Dex (>95%). Northern hybridization studies demonstrated that Dex also elicited similar time- and concentration-dependent increases in the expression of mRNA encoding two components (14 kDa E(2) Ub-conjugating enzyme and Ub) of the ATP-Ub-dependent pathway. The data demonstrate that Dex stimulates preferential hydrolysis of myofibrillar proteins in C(2)C(12) myotubes and suggests that the ATP-Ub-dependent pathway is involved in this response.

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Section: Discussionmentioning

confidence: 99%

Stimulation of myofibrillar protein degradation and expression of mRNA encoding the ubiquitin-proteasome system in C2C12 myotubes by dexamethasone: effect of the proteasome inhibitor MG-132

Thompson¹,

Thom²,

Partridge³

et al. 1999

J. Cell. Phys.

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“…Previous studies have shown that current methodology (high performance liquid chromatography) is able to measure 3-MH release in these quantities when muscle is incubated in the absence of any other amino acids (e.g., Goodman, 1987). However, such conditions may lead to abnormally high degradation rates and we have found that when physiological concentrations of amino acids are present, detection of these levels of 3-MH is not possible.…”

Section: Discussionmentioning

confidence: 70%

“…To overcome these problems, intact muscle incubated 0 1996 WILEY-LISS, INC. in vitro has been used (e.g., Goodman, 1987). However, to investigate the signalling pathway(s1 which regulate 3-MH release in such a model still poses considerable problems of interpretation.…”

mentioning

confidence: 99%

Measurement of protein degradation by release of labelled 3-methylhistidine from skeletal muscle and non-muscle cells

Thompson¹,

Palmer²,

Thom³

et al. 1996

J. Cell. Physiol.

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The rates of [3H]N(tau)-methylhistidine (3-MH) accumulation in the medium, following pulse labelling of cells for 48 h with [3H]methionine, were used to measure myofibrillar protein degradation. In fused C2C12 myotubes, incubation for 24 or 48 h after the labelling period gave rates of myofibrillar degradation of 38 and 42%/day. In a leucine free medium, these rates were similar; 40 and 47%/day, respectively. Using identical conditions +/- leucine, but in the absence of [3H]-methionine, rates of protein accretion and synthesis over 24-48 h were measured. From these data, rates of total protein degradation were calculated by difference and were similar to myofibrillar degradation rates. We have used the same pulse labelling protocol to assess whether the method is applicable to non-muscle cell lines based on the knowledge that 3T3 fibroblasts contain actin in the cytoskeleton. 3-MH was detected both in protein and upon its release into the medium. Actin degradation measured over a 48 h period gave a value half that obtained for total degradation, but the results suggest that the release of 3-MH by fibroblasts in vivo could be appreciable. The development of this methodology should provide a useful tool to investigate signalling mechanisms regulating actin degradation in a variety of cell types.

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“…Previous studies in this (4 -6) and other (7) laboratories have shown that these two agents both stimulate protein synthesis and reduce the release of N -methylhistidine, a marker of myofibrillar protein degradation from intact skeletal muscle in vitro and skeletal muscle cells in culture. However, the mechanism(s) mediating these effects are poorly understood.…”

mentioning

confidence: 83%

“…Although PLD is clearly not involved in the stimulation of protein synthesis by vasopressin, both this agonist and TPA also reduce myofibrillar protein degradation in skeletal muscle (6,7). It remains to be determined whether PLD plays a role in the regulation of this component of protein turnover.…”

Section: Stimulation Of Protein Synthesis By Exogenous Pld-mentioning

confidence: 99%

Regulation of Phospholipase D in L6 Skeletal Muscle Myoblasts

Thompson¹,

Mackie²,

Thom³

et al. 1997

Journal of Biological Chemistry

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The addition of vasopressin or 12-O-tetradecanoylphorbol-13-acetate (TPA) to prelabeled L6 myoblasts elicited increases in [ 14 C]ethanolamine release, suggesting the activation of phospholipase D activity or activities. While the effects of both agonists on intracellular release were rapid and transient, when extracellular release of [ 14 C]ethanolamine was measured, the effect of vasopressin was again rapid and transient, whereas that of TPA was delayed but sustained. Effects of both agonists on intra-and extracellular release were inhibited by the protein kinase C (PKC) inhibitor, Ro-31-8220, and PKC down-regulation by preincubation with TPA. The formation of phosphatidylbutanol elicited by vasopressin and TPA mirrored their effects on extracellular [ 14 C]ethanolamine release in that the former was transient, whereas the latter was sustained. Responses to both agonists were abolished by PKC down-regulation. When protein synthesis was examined, the stimulation of translation by TPA and transcription by vasopressin were inhibited by Ro-31-8220. In contrast, down-regulation of PKC inhibited the synthesis response to TPA but not vasopressin. Furthermore, following down-regulation, the effect of vasopressin was still blocked by the PKC inhibitors, Ro-31-8220 and bisindolylmaleimide. Analysis of PKC isoforms in L6 cells showed the presence of ␣, ⑀, ␦, , , and . Down-regulation removed both cytosolic (␣) and membrane-bound (⑀ and ␦) isoforms. Thus, the elevation of phospholipase D activity or activities induced by both TPA and vasopressin and the stimulation of translation by TPA involves PKC-␣, -⑀, and/or -␦. In contrast, the increase in transcription elicited by vasopressin involves , , and/or . Hence, although phospholipase D may be linked to increases in translation elicited by TPA, it is not involved in the stimulation of transcription by vasopressin.Loss of skeletal muscle is an acute metabolic response to infection and neoplastic disease and results from a decrease in the rate of protein synthesis and an increase in the rate of protein degradation (e.g. see Refs. 1-3). To reverse this process, an understanding of the signaling pathways regulating protein turnover is essential.We have used 12-O-tetradecanoylphorbol-13-acetate (TPA) 1 and vasopressin to investigate the coordinate regulation of protein turnover. Previous studies in this (4 -6) and other (7) laboratories have shown that these two agents both stimulate protein synthesis and reduce the release of N -methylhistidine, a marker of myofibrillar protein degradation from intact skeletal muscle in vitro and skeletal muscle cells in culture. However, the mechanism(s) mediating these effects are poorly understood.Many extracellular signals such as hormones, neurotransmitters, and growth factors elicit their response by activating an intracellular signaling cascade that is initiated by the hydrolysis of membrane phospholipids (8 -11). In L6 skeletal muscle cells, we have demonstrated that TPA and vasopressin stimulate both protein synthesis and a phospholip...

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Acute alterations in sodium flux in vitro lead to decreased myofibrillar protein breakdown in rat skeletal muscle

Cited by 23 publications

References 45 publications

Stimulation of myofibrillar protein degradation and expression of mRNA encoding the ubiquitin-proteasome system in C2C12 myotubes by dexamethasone: effect of the proteasome inhibitor MG-132

Stimulation of myofibrillar protein degradation and expression of mRNA encoding the ubiquitin-proteasome system in C2C12 myotubes by dexamethasone: effect of the proteasome inhibitor MG-132

Measurement of protein degradation by release of labelled 3-methylhistidine from skeletal muscle and non-muscle cells

Regulation of Phospholipase D in L6 Skeletal Muscle Myoblasts

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