title: Amino acids downregulate the expression of several autophagy-related genes in rainbow trout myoblasts.
abstract: Many fish species experience long periods of fasting often associated with seasonal reductions in water temperature and prey availability or spawning migrations. During periods of nutrient restriction, changes in metabolism occur to provide cellular energy via catabolic processes. Muscle is particularly affected by prolonged fasting as proteins of this tissue act as a major energy source. However, the molecular components involved in muscle protein degradation as well as the regulatory networks that control their function are still incompletely defined in fish. The present work aimed to characterize the response of the autophagy-lysosomal degradative pathway to nutrient and serum availability in primary culture of rainbow trout myoblasts. In this aim, 4-day-old cells were incubated in a serum and amino acid-rich medium (complete medium), a serum and amino acid-deprived medium (minimal medium) or a minimal medium plus amino acids, and both the transcription-independent short-term response and the transcription-dependent long-term response of the autophagy-lysosomal degradative pathway were analyzed. We report that serum and amino acids withdrawal is accompanied by a rapid increase of autophagosome formation but also by a slower induction of the expression of several autophagy-related genes (LC3B, gabarapl1, atg4b). We also showed that this latter response is controlled by amino acid (AA) availability and that both TOR-dependent and TOR-independent pathways are involved in this effect. Together these results suggest an important role for AA released by muscle proteolysis during the fasting period in regulating the subtle balance between using proteins as disposable furniture to provide energy, and conserving muscle through protein sparing.
authors.affiliation: INRA, UR1067 Nutrition Métabolisme Aquaculture, St-Pée-sur-Nivelle, France. seiliez@st-pee.inra.fr
authors.forename: Iban
authors.initials: I
authors.lastname: Seiliez
authors.forename: Jean-Charles
authors.initials: JC
authors.lastname: Gabillard
authors.forename: Marine
authors.initials: M
authors.lastname: Riflade
authors.forename: Bastien
authors.initials: B
authors.lastname: Sadoul
authors.forename: Karine
authors.initials: K
authors.lastname: Dias
authors.forename: Julien
authors.initials: J
authors.lastname: Avérous
authors.forename: Sophie
authors.initials: S
authors.lastname: Tesseraud
authors.forename: Sandrine
authors.initials: S
authors.lastname: Skiba
authors.forename: Stéphane
authors.initials: S
authors.lastname: Panserat
mesh_terms: D000596:Amino Acids / Q000494:pharmacology*; D000818:Animals; D001343:Autophagy / Q000187:drug effects* / Q000235:genetics*; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics*; D029941:Fish Proteins / Q000235:genetics / Q000378:metabolism; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism; D032446:Myoblasts / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D017686:Oncorhynchus mykiss / Q000235:genetics*; D010588:Phagosomes / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D044967:Serum / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D020123:Sirolimus / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D013997:Time Factors
chemical_list: D000596:Amino Acids; D029941:Fish Proteins; D036341:Intercellular Signaling Peptides and Proteins; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus