title: HER2-Akt signaling in regulating COP9 signalsome subunit 6 and p53.
abstract: HER2/neu oncogene is frequently overexpressed in various types of cancer, and the (PI3K)-Akt signaling pathway is often activated in HER2-overexpressing cancer cells. CSN6, subunit 6 of the COP9 signalosome complex, is pivotal in regulating MDM2 to destabilize p53, but its upstream regulators remain unclear. Here we show that the HER2-Akt axis is linked to CSN6 regulation, and that Akt is a positive regulator of CSN6. Ectopic expression of Akt can increase the expression of CSN6; accordingly, Akt inhibition leads to CSN6 destabilization. Mechanistic studies show that Akt causes CSN6 phosphorylation at Ser 60, which, in turn, reduces ubiquitin-mediated protein degradation of CSN6. Significantly, Akt's positive impact on CSN6 elevation translates into p53 degradation, potentiating transformational activity and increasing DNA damage. Akt inhibition can attenuate these defects caused by CSN6. These data suggest that Akt is an important positive regulator of CSN6, and that activation of Akt in many types of cancer could lead to abnormal elevation of CSN6 and result in downregulated p53 and increased DNA damage, which promotes cancer cell growth.
authors.affiliation: Department of Pulmonary Medicine, Qilu Hospital of Shandong University, Jinan, Shandong, China.
authors.forename: Yuwen
authors.initials: Y
authors.lastname: Xue
authors.forename: Jian
authors.initials: J
authors.lastname: Chen
authors.forename: Hyun-Ho
authors.initials: HH
authors.lastname: Choi
authors.forename: Liem
authors.initials: L
authors.lastname: Phan
authors.forename: Ping-Chieh
authors.initials: PC
authors.lastname: Chou
authors.forename: Ruiying
authors.initials: R
authors.lastname: Zhao
authors.forename: Huiling
authors.initials: H
authors.lastname: Yang
authors.forename: Janice
authors.initials: J
authors.lastname: Santiago
authors.forename: Mo
authors.initials: M
authors.lastname: Liu
authors.forename: Giselle E
authors.initials: GE
authors.lastname: Yeung
authors.forename: Sai-Ching J
authors.initials: SC
authors.lastname: Yeung
authors.forename: Mong-Hong
authors.initials: MH
authors.lastname: Lee
mesh_terms: D000595:Amino Acid Sequence; D064127:Aurora Kinases; D000075686:COP9 Signalosome Complex; D045744:Cell Line, Tumor; D004249:DNA Damage; D045325:HCT116 Cells; D057809:HEK293 Cells; D006801:Humans; D046912:Multiprotein Complexes / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000378:metabolism*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D055550:Protein Stability; D021122:Protein Subunits / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051736:Proto-Oncogene Proteins c-mdm2 / Q000378:metabolism; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D015398:Signal Transduction; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism; D054875:Ubiquitination
chemical_list: D064127:Aurora Kinases; D000075686:COP9 Signalosome Complex; D046912:Multiprotein Complexes; D010447:Peptide Hydrolases; D017346:Protein Serine-Threonine Kinases; D021122:Protein Subunits; D051057:Proto-Oncogene Proteins c-akt; D051736:Proto-Oncogene Proteins c-mdm2; D018719:Erb-b2 Receptor Tyrosine Kinases; D016159:Tumor Suppressor Protein p53; D025801:Ubiquitin