Down-regulation of genes in the lysosomal and ubiquitin-proteasome proteolytic pathways in calpain-3-deficient muscle.
Calpain-3 deficiency leads to muscular dystrophy in humans and mice and to perturbation of the NFkappaB/IkappaB pathway. As this phenotype is mainly atrophic, this study was performed to determine whether protein turnover and/or proteolytic gene expression was altered in muscles following calpain-3 deficiency. In vitro rates of protein turnover and of substrate ubiquitination, cathepsin B and B+L activities, and mRNA levels for several proteolytic genes were measured in skeletal muscles from 4-5 month-old control and calpain-3 knockout mice. Rates of protein synthesis and breakdown, cathepsin activities, and rates of substrate ubiquitination remained stable in muscles from calpain-3 deficient mice. However, and surprisingly, mRNA levels for cathepsin L, the 14-kDa ubiquitin-conjugating enzyme E2, and the C2 subunit of the 20S proteasome decreased by approximately 47% (P<0.005) in the gastrocnemius muscle from calpain-3 deficient mice. In contrast, muscle mRNA levels for ubiquitin and subunit S5a of the 26S proteasome were unaffected by calpain-3 deficiency. Taken together these data demonstrate that the expression of some genes that are involved in distinct proteolytic pathways is selectively and coordinately down-regulated without any effect on proteolysis. This suggests new pathophysiological hypotheses, e.g. a lack of maturation of NFkappaB precursor and/or a defect in specific substrate targeting.
Combaret
Lydie
L
Human Nutrition Research Center of Clermont-Ferrand, Nutrition and Protein Metabolism Unit, INRA UR551 63122, Ceyrat, France. combaret@clermont.inra.fr <combaret@clermont.inra.fr>
Béchet
Daniel
D
Claustre
Agnès
A
Taillandier
Daniel
D
Richard
Isabelle
I
Attaix
Didier
D
D000818:Animals; D015152:Blotting, Northern; D002154:Calpain / Q000172:deficiency* / Q000235:genetics; D002401:Cathepsin B / Q000378:metabolism; D056668:Cathepsin L; D002403:Cathepsins / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D015536:Down-Regulation; D008247:Lysosomes / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D009097:Multienzyme Complexes / Q000378:metabolism*; D009124:Muscle Proteins; D018482:Muscle, Skeletal / Q000378:metabolism*; D009136:Muscular Dystrophies / Q000235:genetics / Q000378:metabolism*; D010446:Peptide Fragments / Q000172:deficiency* / Q000235:genetics; D010447:Peptide Hydrolases / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D025801:Ubiquitin / Q000378:metabolism*
D009097:Multienzyme Complexes; D009124:Muscle Proteins; D010446:Peptide Fragments; D025801:Ubiquitin; D002403:Cathepsins; D010447:Peptide Hydrolases; D002154:Calpain; C491373:Capn3 protein, mouse; D003546:Cysteine Endopeptidases; D002401:Cathepsin B; C534281:CTSL protein, human; D056668:Cathepsin L; C534278:Ctsl protein, mouse; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease