title: AMP-activated protein kinase induces p53 by phosphorylating MDMX and inhibiting its activity.
abstract: AMP-activated protein kinase (AMPK) has been shown to activate p53 in response to metabolic stress. However, the underlying mechanisms remain unclear. Here we show that metabolic stresses induce AMPK-mediated phosphorylation of human MDMX on Ser342 in vitro and in cells, leading to enhanced association between MDMX and 14-3-3. This markedly inhibits p53 ubiquitylation and significantly stabilizes and activates p53. By striking contrast, no phosphorylation of MDM2 by AMPK was noted. AMPK-mediated MDMX phosphorylation, MDMX-14-3-3 binding, and p53 activation were drastically reduced in mouse embryo fibroblasts harboring endogenous MDMX with S341A (mouse homologue of human serine 342), S367A, and S402A (mouse homologue of human serine 403) mutations. Moreover, deficiency of AMPK prevented MDMX-14-3-3 interaction and p53 activation. The activation of p53 through AMPK-mediated MDMX phosphorylation and inactivation was further confirmed by using cell and animal model systems with two AMPK activators, metformin and salicylate (the active form of aspirin). Together, the results unveil a mechanism by which metabolic stresses activate AMPK, which, in turn, phosphorylates and inactivates MDMX, resulting in p53 stabilization and activation.
authors.affiliation: Department of Biochemistry & Molecular Biology, Tulane University School of Medicine and Tulane Cancer Center, New Orleans, Louisiana, USA.
authors.forename: Guifen
authors.initials: G
authors.lastname: He
authors.forename: Yi-Wei
authors.initials: YW
authors.lastname: Zhang
authors.forename: Jun-Ho
authors.initials: JH
authors.lastname: Lee
authors.forename: Shelya X
authors.initials: SX
authors.lastname: Zeng
authors.forename: Yunyuan V
authors.initials: YV
authors.lastname: Wang
authors.forename: Zhijun
authors.initials: Z
authors.lastname: Luo
authors.forename: X Charlie
authors.initials: XC
authors.lastname: Dong
authors.forename: Benoit
authors.initials: B
authors.lastname: Viollet
authors.forename: Geoffrey M
authors.initials: GM
authors.lastname: Wahl
authors.forename: Hua
authors.initials: H
authors.lastname: Lu
mesh_terms: D048948:14-3-3 Proteins / Q000378:metabolism; D000263:Adenylate Kinase / Q000378:metabolism*; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D059447:Cell Cycle Checkpoints; D018797:Cell Cycle Proteins; D055786:Gene Knockout Techniques; D045325:HCT116 Cells; D057809:HEK293 Cells; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013312:Stress, Physiological; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D054875:Ubiquitination
chemical_list: D048948:14-3-3 Proteins; D018797:Cell Cycle Proteins; C482775:MDM4 protein, human; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D000263:Adenylate Kinase