Regulation of skeletal muscle proteolysis by amino acids.
Skeletal muscle is the major reservoir of body protein that can be mobilized in a number of muscle wasting conditions, that include kidney failure. Increased proteolysis in such conditions provides free amino acids that are used for acute-phase protein synthesis or that are degraded for energy purposes. Amino acids act as signals to regulate both protein synthesis and protein breakdown. We review the current but limited information available on the regulation of proteolytic systems in muscle cells. In particular, recent data have shown that amino acid deprivation in C2C12 myotubes stimulates autophagic sequestration by mechanisms that implicate the Apg system through a class III phosphoinositide-3'-kinase (PI3K III ) signaling cascade.
Béchet
Daniel
D
Human Nutrition Research Center of Clermont-Ferrand, Nutrition and Protein Metabolism Unit, INRA de Theix, Ceyrat, France.
Tassa
Amina
A
Combaret
Lydie
L
Taillandier
Daniel
D
Attaix
Didier
D
D000596:Amino Acids / Q000172:deficiency / Q000502:physiology*; D000818:Animals; D001343:Autophagy; D002154:Calpain / Q000378:metabolism; D020169:Caspases / Q000378:metabolism; D006706:Homeostasis; D006801:Humans; D008247:Lysosomes / Q000201:enzymology; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D018485:Muscle Fibers, Skeletal / Q000201:enzymology; D009124:Muscle Proteins / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000201:enzymology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D015398:Signal Transduction; D025801:Ubiquitin / Q000378:metabolism
D000596:Amino Acids; D009124:Muscle Proteins; D025801:Ubiquitin; D019869:Phosphatidylinositol 3-Kinases; D002154:Calpain; D020169:Caspases; D020778:Matrix Metalloproteinase 2; D046988:Proteasome Endopeptidase Complex