Identification of transmembrane protein 88 (TMEM88) as a dishevelled-binding protein.
Wnt signaling pathways are involved in embryonic development and adult tissue maintenance and have been implicated in tumorigenesis. Dishevelled (Dvl/Dsh) protein is one of key components in Wnt signaling and plays essential roles in regulating these pathways through protein-protein interactions. Identifying and characterizing Dvl-binding proteins are key steps toward understanding biological functions. Given that the tripeptide VWV (Val-Trp-Val) binds to the PDZ domain of Dvl, we searched publically available databases to identify proteins containing the VWV motif at the C terminus that could be novel Dvl-binding partners. On the basis of the cellular localization and expression patterns of the candidates, we selected for further study the TMEM88 (target protein transmembrane 88), a two-transmembrane-type protein. The interaction between the PDZ domain of Dvl and the C-terminal tail of TMEM88 was confirmed by using NMR and fluorescence spectroscopy. Furthermore, in HEK293 cells, TMEM88 attenuated the Wnt/β-catenin signaling induced by Wnt-1 ligand in a dose-dependent manner, and TMEM88 knockdown by RNAi increased Wnt activity. In Xenopus, TMEM88 protein is sublocalized at the cell membrane and inhibits Wnt signaling induced by Xdsh but not β-catenin. In addition, TMEM88 protein inhibits the formation of a secondary axis normally induced by Xdsh. The findings suggest that TMEM88 plays a role in regulating Wnt signaling. Indeed, analysis of microarray data revealed that the expression of the Tmem88 gene was strongly correlated with that of Wnt signaling-related genes in embryonic mouse intestines. Together, we propose that TMEM88 associates with Dvl proteins and regulates Wnt signaling in a context-dependent manner.
Department of Structural Biology, St Jude Children’s Research Hospital, Memphis, Tennessee 38105, USA.
Ho-Jin
HJ
Lee
David
D
Finkelstein
Xiaofeng
X
Li
Dianqing
D
Wu
De-Li
DL
Shi
Jie J
JJ
Zheng
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D000072261:Dishevelled Proteins; D006801:Humans; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000378:metabolism*; D011485:Protein Binding; D025941:Protein Interaction Mapping; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D051155:Wnt1 Protein / Q000378:metabolism; D014981:Xenopus; D029867:Xenopus Proteins
D048868:Adaptor Proteins, Signal Transducing; C000606586:DVL1 protein, Xenopus; D000072261:Dishevelled Proteins; D008024:Ligands; D008565:Membrane Proteins; D010750:Phosphoproteins; C555652:TMEM88 protein, human; C555653:TMEM88 protein, mouse; C495247:WNT1 protein, human; D051155:Wnt1 Protein; C495246:Wnt1 protein, mouse; D029867:Xenopus Proteins