EBP50, a beta-catenin-associating protein, enhances Wnt signaling and is over-expressed in hepatocellular carcinoma.
Wnt signaling mediated by beta-catenin plays crucial roles in the development of hepatocellular carcinoma and other cancers such as colorectal cancer. beta-Catenin associates with T-cell factor (TCF) transcription factors and functions as a transcriptional activator in the nucleus. By protein interaction screening, we identified EBP50, a cytoplasmic protein with 2 PDZ domains, as a beta-catenin-associating molecule. EBP50 interacted with beta-catenin through its carboxyl-PDZ domain in vitro and in vivo. Northern blot and RT-PCR analysis revealed an increase of EBP50 messenger RNA (mRNA) in hepatocellular carcinoma (HCC) cell lines and surgical specimens of human HCC. Over-expression of EBP50 protein with focal nuclear localization was detected in human HCC. In human HCC and colorectal cancer cell lines, EBP50 enhanced beta-catenin/TCF-dependent transcription in a dose-dependent manner. In an HCC cell line, over-expression of the carboxyl PDZ domain resulted in a decrease of endogenous beta-catenin/TCF transactivation. EBP50 promoted beta-catenin-mediated transactivation only in cells in which beta-catenin was already stabilized, suggesting that EBP50 may work with stabilized beta-catenin for transcriptional regulation. In conclusion, the EBP50/beta-catenin complex promotes Wnt signaling, and over-expression of EBP50 may work cooperatively with beta-catenin in the development of liver cancer.
Shibata
Tatsuhiro
T
Pathology Division, National Cancer Center Research Institute, Tokyo, Japan.
Chuma
Makoto
M
Kokubu
Akiko
A
Sakamoto
Michiie
M
Hirohashi
Setsuo
S
D006528:Carcinoma, Hepatocellular; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D003598:Cytoskeletal Proteins / Q000737:chemistry / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D008113:Liver Neoplasms; D010750:Phosphoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D017923:Sodium-Hydrogen Exchangers; D015534:Trans-Activators / Q000737:chemistry / Q000378:metabolism*; D015533:Transcriptional Activation / Q000502:physiology; D051153:Wnt Proteins; D029961:Zebrafish Proteins; D051176:beta Catenin
C495270:CTNNB1 protein, human; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; D017923:Sodium-Hydrogen Exchangers; D015534:Trans-Activators; D051153:Wnt Proteins; D029961:Zebrafish Proteins; D051176:beta Catenin; C093376:sodium-hydrogen exchanger regulatory factor