title: Ubiquitin ligase CHIP induces TRAF2 proteasomal degradation and NF-κB inactivation to regulate breast cancer cell invasion.
abstract: Transcriptional factor nuclear factor-kappaB (NF-κB) plays a crucial role in human breast cancer cell invasion and metastasis. The carboxyl terminus of Hsc70-interacting protein (CHIP) is a U-box-type ubiquitin ligase that induces ubiquitination and proteasomal degradation of its substrate proteins. In this study, we investigated the role of CHIP in the NF-κB pathway in the invasion of MDA-MB-231 cells, a highly aggressive breast cancer cell line. We showed that overexpression of CHIP significantly inhibits the invasion of the MDA-MB-231 cells. The overexpression of CHIP suppressed expression of urokinase plasminogen activator (uPA) and matrix metalloproteinase-9 (MMP-9) in MDA-MB-231 cells. Moreover, CHIP strongly inhibited the nuclear localization and the transcriptional activity of NF-κB. The activation of the IkappaB kinase complex (IKK) was also blocked by CHIP overexpression. Importantly, CHIP overexpression resulted in a significant decrease in the level of TNF receptor-associated factor 2 (TRAF2), an upstream key player in the NF-κB pathway. However, the level of TRAF2 was restored after treatment with a proteasome inhibitor, MG-132. Moreover, CHIP overexpression promoted the ubiquitination of TRAF2. We also found cell invasion significantly decreased in cells transfected with TRAF2 small interfering RNA (siRNA). In contrast, when CHIP expression was suppressed by siRNA in poorly invasive MCF-7 cells, cell invasion significantly increased in conjunction with enhanced NF-κB activation and TRAF2 levels. Taken together, these results suggest that CHIP regulates NF-κB-mediated cell invasion via the down-regulation of TRAF2.
authors.affiliation: Graduate Program in Science for Aging & Yonsei Research Institute of Aging Science, Yonsei University, Seoul 120-749, Korea.
authors.forename: Kang Won
authors.initials: KW
authors.lastname: Jang
authors.forename: Kyung Hye
authors.initials: KH
authors.lastname: Lee
authors.forename: Soo Hyuk
authors.initials: SH
authors.lastname: Kim
authors.forename: Taewon
authors.initials: T
authors.lastname: Jin
authors.forename: Eun Young
authors.initials: EY
authors.lastname: Choi
authors.forename: Hyun Ju
authors.initials: HJ
authors.lastname: Jeon
authors.forename: Eunsuk
authors.initials: E
authors.lastname: Kim
authors.forename: Ye Sun
authors.initials: YS
authors.lastname: Han
authors.forename: Ji Hyung
authors.initials: JH
authors.lastname: Chung
mesh_terms: D001483:Base Sequence; D001943:Breast Neoplasms / Q000201:enzymology / Q000378:metabolism / Q000473:pathology*; D045744:Cell Line, Tumor; D017931:DNA Primers; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006801:Humans; D016328:NF-kappa B / Q000378:metabolism*; D009361:Neoplasm Invasiveness; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D059748:Proteolysis; D060888:Real-Time Polymerase Chain Reaction; D047992:TNF Receptor-Associated Factor 2 / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D016328:NF-kappa B; D047992:TNF Receptor-Associated Factor 2; C467728:STUB1 protein, human; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex