title: MAFbx/Atrogin-1 controls the activity of the initiation factor eIF3-f in skeletal muscle atrophy by targeting multiple C-terminal lysines.
abstract: We recently presented evidence that the subunit eIF3-f of the eukaryotic initiation translation factor eIF3 that interacts with the E3-ligase Atrogin-1/muscle atrophy F-box (MAFbx) for polyubiquitination and proteasome-mediated degradation is a key target that accounts for MAFbx function during muscle atrophy. To understand this process, deletion analysis was used to identify the region of eIF3-f that is required for its proteolysis. Here, we report that the highly conserved C-terminal domain of eIF3-f is implicated for MAFbx-directed polyubiquitination and proteasomal degradation. Site-directed mutagenesis of eIF3-f revealed that the six lysine residues within this domain are required for full polyubiquitination and degradation by the proteasome. In addition, mutation of these six lysines (mutant K(5-10)R) displayed hypertrophic activity in cellulo and in vivo and was able to protect against starvation-induced muscle atrophy. Taken together, our data demonstrate that the C-terminal modifications, believed to be critical for proper eIF3-f regulation, are essential and contribute to a fine-tuning mechanism that plays an important role for eIF3-f function in skeletal muscle.
authors.affiliation: Université de Montpellier-Sud de France.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Csibi
authors.forename: Marie Pierre
authors.initials: MP
authors.lastname: Leibovitch
authors.forename: Karen
authors.initials: K
authors.lastname: Cornille
authors.forename: Lionel A
authors.initials: LA
authors.lastname: Tintignac
authors.forename: Serge A
authors.initials: SA
authors.lastname: Leibovitch
mesh_terms: D000818:Animals; D002460:Cell Line; D039621:Eukaryotic Initiation Factor-3 / Q000235:genetics / Q000378:metabolism*; D008239:Lysine / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000473:pathology; D009133:Muscular Atrophy / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D016297:Mutagenesis, Site-Directed; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary / Q000235:genetics; D044843:SKP Cullin F-Box Protein Ligases / Q000235:genetics / Q000378:metabolism*; D013217:Starvation / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D054875:Ubiquitination / Q000235:genetics
chemical_list: D039621:Eukaryotic Initiation Factor-3; D009124:Muscle Proteins; C486691:Fbxo32 protein, mouse; D044843:SKP Cullin F-Box Protein Ligases; D046988:Proteasome Endopeptidase Complex; D008239:Lysine