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Development of an in-vitro model system to investigate the mechanism of muscle protein catabolism induced by proteolysis-inducing factor.

Gomes-Marcondes MC, Smith HJ, Cooper JC, Tisdale MJ - Br. J. Cancer (2002)

Bottom Line: In myoblasts this followed a bell-shaped dose-response curve with maximal effects at a proteolysis-inducing factor concentration between 2 and 4 nM, while in myotubes increased protein degradation was seen at all concentrations of proteolysis-inducing factor up to 10 nM, again with a maximum of 4 nM proteolysis-inducing factor.There was also an increased expression of the 19S regulatory complex as well as the ubiquitin-conjugating enzyme (E2(14k)), and in myotubes a decrease in myosin expression was seen with increasing concentrations of proteolysis-inducing factor.These results show that proteolysis-inducing factor co-ordinately upregulates both ubiquitin conjugation and proteasome activity in both myoblasts and myotubes and may play an important role in the muscle wasting seen in cancer cachexia.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology and Biophysics, University of Campinas, UNICAMP, SP, Brazil 13083-970. M.J.Tisdale@aston.ac.uk

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(A) Effect of PIF on total protein degradation in C2C12 myotubes after 24 h (×) and 48 h (solid square) incubation. Measurements were made in the presence of excess (2 mM) phenylalanine and are the average of nine determinations. Differences from controls in the absence of PIF are indicated as a, P<0.05 and b, P<0.01. (B) Chymotryptic activity of soluble extracts of C2C12 myotubes after treatment with PIF for 24 h. Values shown represent mean±s.e.m where n=8. Differences from controls in the absence of PIF are shown as a, P<0.05 and b, P<0.01.
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fig4: (A) Effect of PIF on total protein degradation in C2C12 myotubes after 24 h (×) and 48 h (solid square) incubation. Measurements were made in the presence of excess (2 mM) phenylalanine and are the average of nine determinations. Differences from controls in the absence of PIF are indicated as a, P<0.05 and b, P<0.01. (B) Chymotryptic activity of soluble extracts of C2C12 myotubes after treatment with PIF for 24 h. Values shown represent mean±s.e.m where n=8. Differences from controls in the absence of PIF are shown as a, P<0.05 and b, P<0.01.

Mentions: Further studies were carried out using C2C12 myotubes, since these contain the myofibrillar proteins actin and myosin, characteristic of skeletal muscle. The effect of PIF on total protein catabolism, as determined by [3H]phenylalanine release is shown in Figure 4AFigure 4


Development of an in-vitro model system to investigate the mechanism of muscle protein catabolism induced by proteolysis-inducing factor.

Gomes-Marcondes MC, Smith HJ, Cooper JC, Tisdale MJ - Br. J. Cancer (2002)

(A) Effect of PIF on total protein degradation in C2C12 myotubes after 24 h (×) and 48 h (solid square) incubation. Measurements were made in the presence of excess (2 mM) phenylalanine and are the average of nine determinations. Differences from controls in the absence of PIF are indicated as a, P<0.05 and b, P<0.01. (B) Chymotryptic activity of soluble extracts of C2C12 myotubes after treatment with PIF for 24 h. Values shown represent mean±s.e.m where n=8. Differences from controls in the absence of PIF are shown as a, P<0.05 and b, P<0.01.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2746596&req=5

fig4: (A) Effect of PIF on total protein degradation in C2C12 myotubes after 24 h (×) and 48 h (solid square) incubation. Measurements were made in the presence of excess (2 mM) phenylalanine and are the average of nine determinations. Differences from controls in the absence of PIF are indicated as a, P<0.05 and b, P<0.01. (B) Chymotryptic activity of soluble extracts of C2C12 myotubes after treatment with PIF for 24 h. Values shown represent mean±s.e.m where n=8. Differences from controls in the absence of PIF are shown as a, P<0.05 and b, P<0.01.
Mentions: Further studies were carried out using C2C12 myotubes, since these contain the myofibrillar proteins actin and myosin, characteristic of skeletal muscle. The effect of PIF on total protein catabolism, as determined by [3H]phenylalanine release is shown in Figure 4AFigure 4

Bottom Line: In myoblasts this followed a bell-shaped dose-response curve with maximal effects at a proteolysis-inducing factor concentration between 2 and 4 nM, while in myotubes increased protein degradation was seen at all concentrations of proteolysis-inducing factor up to 10 nM, again with a maximum of 4 nM proteolysis-inducing factor.There was also an increased expression of the 19S regulatory complex as well as the ubiquitin-conjugating enzyme (E2(14k)), and in myotubes a decrease in myosin expression was seen with increasing concentrations of proteolysis-inducing factor.These results show that proteolysis-inducing factor co-ordinately upregulates both ubiquitin conjugation and proteasome activity in both myoblasts and myotubes and may play an important role in the muscle wasting seen in cancer cachexia.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology and Biophysics, University of Campinas, UNICAMP, SP, Brazil 13083-970. M.J.Tisdale@aston.ac.uk

Show MeSH
Related in: MedlinePlus