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Lookup NU author(s): Dr Michael Thompson
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Addition of the synthetic glucocorticoid, dexamethasone (Dex) to serum- deprived C2C12 myotubes elicited time- and concentration-dependent changes in N(γ)-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 E2 Ub-conjugating enzyme and Ub) of the ATP-Ub-dependent pathway. The data demonstrate that Dex stimulates preferential hydrolysis of myofibrillar proteins in C2C12 myotubes and suggests that the ATP-Ub-dependent pathway is involved in this response.
Author(s): Thompson MG, Thom A, Partridge K, Garden K, Campbell GP, Calder G, Palmer RM
Publication type: Article
Publication status: Published
Journal: Journal of Cellular Physiology
Year: 1999
Volume: 181
Issue: 3
Pages: 455-461
Print publication date: 01/01/1999
ISSN (print): 00219541
ISSN (electronic):
DOI: 10.1002/(SICI)1097-4652(199912)181:3<455::AID-JCP9>3.0.CO;2-K
PubMed id: 10528231
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