P.41 Inhibition of protein synthesis and of ubiquitinproteasomeproteolysis in murine skeletal muscle following chemotherapy

Tilignac, Thomas; Temparis, Sandrine; Rallière, Cécile; Taillandier, Daniel; Madelmont, Jean‐Claude; Attaix, Didier

doi:10.1016/s0261-5614(98)80197-0

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“…These data were repeatedly obtained in two different experiments and were confirmed by measuring proteasome activities using another technique (i.e. partially purified proteasomes on a glycerol gradient (Tilignac et al 2002; Combaret et al 2004; data not shown)). However, rates of ubiquitination also tended to decrease ( P < 0.06) in the PP state in the 22‐month‐old animals (Fig.…”

Section: Discussionsupporting

confidence: 58%

“…Total RNA was extracted (Chomczynski & Sacchi, 1987), and Northern blots were performed as previously described (Combaret et al 2004). The membranes were hybridized with cDNA probes encoding polyUb, the 14‐kDa E2, and the C2 and X subunits of the 20S proteasome (Mansoor et al 1996; Tilignac et al 2002; Combaret et al 2004). The hybridizations were performed with [ 32 P] cDNA fragments labelled by random priming.…”

Section: Methodsmentioning

confidence: 99%

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A leucine‐supplemented diet restores the defective postprandial inhibition of proteasome‐dependent proteolysis in aged rat skeletal muscle

Combaret

Dardevet

Rieu

et al. 2005

The Journal of Physiology

134

109

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We tested the hypothesis that skeletal muscle ubiquitin-proteasome-dependent proteolysis is dysregulated in ageing in response to feeding. In Experiment 1 we measured rates of proteasome-dependent proteolysis in incubated muscles from 8-and 22-month-old rats, proteasome activities, and rates of ubiquitination, in the postprandial and postabsorptive states. Peptidase activities of the proteasome decreased in the postabsorptive state in 22-month-old rats compared with 8-month-old animals, while the rate of ubiquitination was not altered. Furthermore, the down-regulation of in vitro proteasome-dependent proteolysis that prevailed in the postprandial state in 8-month-old rats was defective in 22-month-old rats. Next, we tested the hypothesis that the ingestion of a 5% leucine-supplemented diet may correct this defect. Leucine supplementation restored the postprandial inhibition of in vitro proteasome-dependent proteolysis in 22-month-old animals, by down-regulating both rates of ubiquitination and proteasome activities. In Experiment 2, we verified that dietary leucine supplementation had long-lasting effects by comparing 8-and 22-month-old rats that were fed either a leucine-supplemented diet or an alanine-supplemented diet for 10 days. The inhibited in vitro proteolysis was maintained in the postprandial state in the 22-month-old rats fed the leucine-supplemented diet. Moreover, elevated mRNA levels for ubiquitin, 14-kDa ubiquitin-conjugating enzyme E2, and C2 and X subunits of the 20S proteasome that were characteristic of aged muscle were totally suppressed in 22-month-old animals chronically fed the leucine-supplemented diet, demonstrating an in vivo effect. Thus the defective postprandial down-regulation of in vitro proteasome-dependent proteolysis in 22-month-old rats was restored in animals chronically fed a leucine-supplemented diet.

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Section: Discussionsupporting

confidence: 58%