title: FBXO32 Targets c-Myc for Proteasomal Degradation and Inhibits c-Myc Activity.
abstract: FBXO32 (MAFbx/Atrogin-1) is an E3 ubiquitin ligase that is markedly up-regulated in muscle atrophy. Although some data indicate that FBXO32 may play an important role in tumorigenesis, the molecular mechanism of FBXO32 in tumorigenesis has been poorly understood. Here, we present evidence that FBXO32 targets the oncogenic protein c-Myc for ubiquitination and degradation through the proteasome pathway. Phosphorylation of c-Myc at Thr-58 and Ser-62 is dispensable for FBXO32 to induce c-Myc degradation. Mutation of the lysine 326 in c-Myc reduces c-Myc ubiquitination and prevents the c-Myc degradation induced by FBXO32. Furthermore, overexpression of FBXO32 suppresses c-Myc activity and inhibits cell growth, but knockdown of FBXO32 enhances c-Myc activity and promotes cell growth. Finally, we show that FBXO32 is a direct downstream target of c-Myc, highlighting a negative feedback regulation loop between c-Myc and FBXO32. Thus, FBXO32 may function by targeting c-Myc. This work explains the function of FBXO32 and highlights its mechanisms in tumorigenesis.
authors.affiliation: From the Key Laboratory of Aquatic Biodiversity and Conservation and.
authors.forename: Zhichao
authors.initials: Z
authors.lastname: Mei
authors.affiliation: From the Key Laboratory of Aquatic Biodiversity and Conservation and.
authors.forename: Dawei
authors.initials: D
authors.lastname: Zhang
authors.affiliation: From the Key Laboratory of Aquatic Biodiversity and Conservation and.
authors.forename: Bo
authors.initials: B
authors.lastname: Hu
authors.affiliation: From the Key Laboratory of Aquatic Biodiversity and Conservation and.
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.affiliation: the First Hospital of Wenzhou Medical University, Wenzhou 325000, China.
authors.forename: Xian
authors.initials: X
authors.lastname: Shen
authors.affiliation: From the Key Laboratory of Aquatic Biodiversity and Conservation and the State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China and w-xiao@ihb.ac.cn.
authors.forename: Wuhan
authors.initials: W
authors.lastname: Xiao
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D049109:Cell Proliferation; D006801:Humans; D051379:Mice; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism; D009133:Muscular Atrophy / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D011485:Protein Binding; D059748:Proteolysis; D016271:Proto-Oncogene Proteins c-myc / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D044843:SKP Cullin F-Box Protein Ligases / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination
chemical_list: D009124:Muscle Proteins; D016271:Proto-Oncogene Proteins c-myc; C440907:FBXO32 protein, human; D044843:SKP Cullin F-Box Protein Ligases; D046988:Proteasome Endopeptidase Complex
keywords: FBXO32; Myc (c-Myc); cell proliferation; muscle atrophy; oncogene; proteasomal degradation; ubiquitylation (ubiquitination)