Skeletal muscle protein synthesis and the abundance of the mRNA translation initiation repressor PDCD4 are inversely regulated by fasting and refeeding in rats.

Published

Journal Article

Optimal skeletal muscle mass is vital to human health, because defects in muscle protein metabolism underlie or exacerbate human diseases. The mammalian target of rapamycin complex 1 is critical in the regulation of mRNA translation and protein synthesis. These functions are mediated in part by the ribosomal protein S6 kinase 1 (S6K1) through mechanisms that are poorly understood. The tumor suppressor programmed cell death 4 (PDCD4) has been identified as a novel substrate of S6K1. Here, we examined 1) the expression of PDCD4 in skeletal muscle and 2) its regulation by feed deprivation (FD) and refeeding. Male rats (~100 g; n = 6) were subjected to FD for 48 h; some rats were refed for 2 h. FD suppressed muscle fractional rates of protein synthesis and Ser(67) phosphorylation of PDCD4 (-50%) but increased PDCD4 abundance (P < 0.05); refeeding reversed these changes (P < 0.05). Consistent with these effects being regulated by S6K1, activation of this kinase was suppressed by FD (-91%, P < 0.05) but was increased by refeeding. Gavaging rats subjected to FD with a mixture of amino acids partially restored muscle fractional rates of protein synthesis and reduced PDCD4 abundance relative to FD. Finally, when myoblasts were grown in amino acid- and serum-free medium, phenylalanine incorporation into proteins in cells depleted of PDCD4 more than doubled the values in cells with a normal level of PDCD4 (P < 0.0001). Thus feeding stimulates fractional protein synthesis in skeletal muscle in parallel with the reduction of the abundance of this mRNA translation inhibitor.

Full Text

Duke Authors

Cited Authors

  • Zargar, S; Moreira, TS; Samimi-Seisan, H; Jeganathan, S; Kakade, D; Islam, N; Campbell, J; Adegoke, OAJ

Published Date

  • June 2011

Published In

Volume / Issue

  • 300 / 6

Start / End Page

  • E986 - E992

PubMed ID

  • 21406616

Pubmed Central ID

  • 21406616

Electronic International Standard Serial Number (EISSN)

  • 1522-1555

Digital Object Identifier (DOI)

  • 10.1152/ajpendo.00642.2010

Language

  • eng

Conference Location

  • United States