Putative tumor suppressor EDD interacts with and up-regulates APC.
Adenomatous polyposis coli (APC), whose mutation causes colorectal cancers, is a key player in the Wnt signaling pathway. While the role of APC in inhibition of beta-catenin/LEF1-dependent activation of transformation-inducing genes has been intensively studied and well established, regulation of APC expression at the protein level is only partially understood. Here we report that APC is up-regulated by EDD, the mammalian orthologue of Drosophila melanogaster"hyperplastic discs" gene (hyd) that is considered to be a putative tumor suppressor. Screening of APC immunocomplexes by mass spectrometry identified EDD as a putative APC-interacting protein. Exogenously expressed and endogenous APC interacted with EDD in vivo. Indirect immunofluorescent analyses demonstrated that APC and EDD co-localized in the cytoplasm of the cell. Over-expression of EDD enhanced the protein expression level of APC and its binding partner Axin, resulting in inhibition of Wnt signaling downstream of beta-catenin. Conversely, siRNA knock-down of EDD down-regulated APC at the protein level without altering its mRNA level, causing enhanced protein expression of beta-catenin. Thus, through protein-protein interaction, EDD stabilizes APC and up-regulates APC's function to inhibit beta-catenin, suggesting that EDD could act as a colorectal tumor suppressor.
Ohshima
Ryuichi
R
Division of Gastroenterological Surgery, Department of Surgery, St. Marianna University School of Medicine, Kawasaki 216-8511, Japan.
Ohta
Tomohiko
T
Wu
Wenwen
W
Koike
Ayaka
A
Iwatani
Tsuguo
T
Henderson
Michelle
M
Watts
Colin K W
CK
Otsubo
Takehito
T
D011125:Adenomatous Polyposis Coli / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D025601:Adenomatous Polyposis Coli Protein / Q000502:physiology*; D015179:Colorectal Neoplasms / Q000235:genetics; D029721:Drosophila Proteins; D015972:Gene Expression Regulation, Neoplastic; D016147:Genes, Tumor Suppressor; D006367:HeLa Cells; D006801:Humans; D015534:Trans-Activators / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases; D015854:Up-Regulation; D051155:Wnt1 Protein / Q000502:physiology; D051176:beta Catenin
D025601:Adenomatous Polyposis Coli Protein; D029721:Drosophila Proteins; D015534:Trans-Activators; D025521:Tumor Suppressor Proteins; D051155:Wnt1 Protein; D051176:beta Catenin; C471151:hyd protein, Drosophila; D044767:Ubiquitin-Protein Ligases