WWOX binds the specific proline-rich ligand PPXY: identification of candidate interacting proteins.
WWOX, the gene that maps to common chromosomal fragile site FRA16D, is frequently affected by aberrations in multiple types of cancers. WWOX encodes a 46 kDa protein that contains two WW domains and a short-chain oxidoreductase (SDR) domain. We recently demonstrated that ectopic expression of WWOX inhibits xenograft tumor growth of tumorigenic breast cancer cells. Little is known of the biochemical function(s) of WWOX. The SDR domain is predicted to be involved in sex-steroid metabolism and the WW domains are likely involved in protein-protein interactions. In this report, we identify the specific proline-rich ligand for WWOX as PPXY and show that the amino-terminal WW domain is responsible for this interaction. Using the WWOX WW domains as a probe, we screened high-density protein arrays and identified five candidate-binding partners. The binding to one of these candidates, small membrane protein of the lysosome/late endosome (SIMPLE), was further analysed, and we observed that a specific PPSY motif in the SIMPLE amino-acid sequence was required to interact with the amino-terminal WW domain of WWOX. In addition, immunofluorescence staining demonstrated that endogenous WWOX and SIMPLE co-localize to perinuclear compartments of MCF-7 human breast cancer cells. These studies demonstrate that WWOX contains a Group I WW domain that binds known cellular proteins containing the specific ligand PPXY. Identification and characterization of WWOX interacting proteins will lead to an understanding of the biological functions of WWOX in normal and tumor cells.
Ludes-Meyers
John H
JH
Department of Carcinogenesis, University of Texas, MD Anderson Cancer Center, Science Park-Research Division, PO Box 389, Smithville, TX 78957-0389, USA.
Kil
Hyunsuk
H
Bednarek
Andrzej K
AK
Drake
Jeff
J
Bedford
Mark T
MT
Aldaz
C Marcelo
CM
D000595:Amino Acid Sequence; D001665:Binding Sites; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D008024:Ligands; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism; D010088:Oxidoreductases / Q000378:metabolism*; D011392:Proline / Q000031:analogs & derivatives / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D014157:Transcription Factors / Q000378:metabolism; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins; D000074584:WW Domain-Containing Oxidoreductase
C118738:LITAF protein, human; D008024:Ligands; D009687:Nuclear Proteins; C487612:PPXY ligand; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D011392:Proline; D010088:Oxidoreductases; D000074584:WW Domain-Containing Oxidoreductase; C486071:WWOX protein, human