Simvastatin represses protein synthesis in the muscle-derived C₂C₁₂cell line with a concomitant reduction in eukaryotic initiation factor 2B expression

Abstract

Tuckow AP, Jefferson SJ, Kimball SR, Jefferson LS. Simvastatin represses protein synthesis in the muscle-derived C 2C12 cell line with a concomitant reduction in eukaryotic initiation factor 2B expression. Am J Physiol Endocrinol Metab 300: E564 -E570, 2011. First published January 11, 2011; doi:10.1152/ajpendo.00383.2010Statins are a widely prescribed class of cholesterol lowering drugs whose use is frequently associated with muscle-related ailments. A number of mechanisms have been implicated in statin-induced myotoxicity including alterations in both protein synthesis and protein degradation. The objective of the present study was to explore the mechanism(s) contributing to the statin-induced reduction in protein synthesis in the muscle-derived C 2C12 cell line. Cells were treated with 10 M simvastatin or vehicle alone for 24 h in 1% serum. Cells exposed to simvastatin exhibited reduced rates of protein synthesis, as evidenced by [35 S]methionine and [ 35 S]cysteine incorporation into protein. The reduction in protein synthesis occurred with a concomitant decrease in expression and activity of eukaryotic initiation factor 2B (eIF2B), a regulated and rate-controlling guanine nucleotide exchange factor known to affect global rates of protein synthesis. The reductions in protein synthesis and eIF2B expression were prevented by coincubation with mevalonate. Simvastatin treatment also resulted in a proteasome-sensitive reduction in the protein expression of all the subunits of the eIF2B heteropentameric complex. Finally, increased phosphorylation of the catalytic ⑀-subunit at Ser 535 was observed, an event consistent with an observed reduction in eIF2B activity. These results suggest that repression of eIF2B expression and activity may contribute, at least in part, to the statin-induced reduction in protein synthesis.messenger RNA translation; 3-hydroxy-3-methylglutaryl coenzyme A-reductase; myoblasts; myotubes STATINS [3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors] are a widely prescribed and effective class of lipid lowering drugs that have demonstrated enormous clinical benefit not only for reducing cardiovascular risk (26) but also for several additional and unexpected pleiotropic benefits (e.g., anti-inflammatory and immunomodulatory effects) (10, 23). One of the less desirable effects of statin use is the incidence of myopathies ranging from complaints of muscle pain and weakness (i.e., myalgia) to the most severe case of rhabdomyolysis, which is rare but can be fatal (2, 34). The mechanisms implicated in the myotoxic effects of statins are still poorly understood. Recently, statins have been shown to upregulate the "atrogenes" MAFbx and/or MuRF-1 in human, zebrafish, and rodent skeletal muscle, which may contribute to increased rates of muscle proteolysis (4,11,21). In addition to enhanced proteolysis, other groups have reported decrements in the rate of protein synthesis in embryonic chick cardiomyocytes (28) and rat primary myocytes (8, 22), although the mechanism for the repression...

Role of p70S6K1-mediated Phosphorylation of eIF4B and PDCD4 Proteins in the Regulation of Protein Synthesis

“…Lysates were rocked at 4°C for 30 min and centrifuged at 1,000 ϫ g for 5 min. Global rates of protein synthesis were calculated by the incorporation of [ 35 S]methionine and [ 35 S]cysteine into TCA-precipitable protein as described previously (16). HA-tagged constitutively active S6K1 expression plasmid was a kind gift from Dr. John Blenis (Harvard Medical School) and has been described previously (17).…”

The AKT/mTOR signaling pathway plays a key role in statin-induced myotoxicity

“…Different factors could play a role; for example impaired mitochondrial function [8,9], induction of skeletal muscle breakdown due to increased expression of atrogin-1/MaFbx [10], reduction of skeletal muscle protein synthesis [11], inhibition of small GTPases due to impaired prenylation [12] and/or impaired creatine synthesis [13].…”

A short-term statin treatment changes the contractile properties of fast-twitch skeletal muscles

“…These fibers appear to be especially prone to SIM-induced dysfunction and necrosis [29–31]. The failure to preserve physiological resting cytosolic Ca 2+ concentrations in SIM may potentially activate the calpain Ca 2+− dependant proteolytic pathway [21], repress protein synthesis [32, 33], and stimulate the ubiquitin-proteasome system [34, 35], favoring atrophy [33], myocellular damage [34] and, ultimately, apoptosis [36, 37]. …”