title: Dapper 1 antagonizes Wnt signaling by promoting dishevelled degradation.
abstract: Wnt signaling plays pivotal roles in the regulation of embryogenesis and cancer development. Xenopus Dapper (Dpr) was identified as an interacting protein for Dishevelled (Dvl), a Wnt signaling mediator, and modulates Wnt signaling. However, it is largely unclear how Dpr regulates Wnt signaling. Here, we present evidence that human Dpr1, the ortholog of Xenopus Dpr, inhibits Wnt signaling. We have identified the regions responsible for the Dpr-Dvl interaction in both proteins and found that the interaction interface is formed between the DEP (Dishevelled, Egl-10, and pleckstrin) domain of Dvl and the central and the C-terminal regions of Dpr1. The inhibitory function of human Dpr1 requires both its N and C terminus. Overexpression of the C-terminal region corresponding to the last 225 amino acids of Dpr1, in contrast to wild-type Dpr1, enhances Wnt signaling, suggesting a dominant negative function of this region. Furthermore, we have shown that Dpr1 induces Dvl degradation via a lysosome inhibitor-sensitive and proteasome inhibitor-insensitive mechanism. Knockdown of Dpr1 by RNA interference up-regulates endogenous Dvl2 protein. Taken together, our data indicate that the inhibitory activity of Dpr on Wnt signaling is conserved from Xenopus to human and that Dpr1 antagonizes Wnt signaling by inducing Dvl degradation.
authors.affiliation: State Key Laboratory of Biomembrane and Membrane Biotechnology, Department of Biological Sciences and Biotechnology, Tsinghua University, Beijing 100084, China.
authors.forename: Long
authors.initials: L
authors.lastname: Zhang
authors.forename: Xia
authors.initials: X
authors.lastname: Gao
authors.forename: Jun
authors.initials: J
authors.lastname: Wen
authors.forename: Yuanheng
authors.initials: Y
authors.lastname: Ning
authors.forename: Ye-Guang
authors.initials: YG
authors.lastname: Chen
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000032:analysis / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D000595:Amino Acid Sequence; D002460:Cell Line; D000072261:Dishevelled Proteins; D004305:Dose-Response Relationship, Drug; D005452:Fluoresceins; D019085:Fluorescent Antibody Technique, Direct; D005456:Fluorescent Dyes; D017930:Genes, Reporter; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D007211:Indoles; D008156:Luciferases / Q000378:metabolism; D008163:Luminescent Measurements; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D010750:Phosphoproteins / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D010957:Plasmids; D011233:Precipitin Tests; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D012235:Rhodamines; D015398:Signal Transduction; D014162:Transfection; D051153:Wnt Proteins / Q000032:analysis / Q000037:antagonists & inhibitors*; D029867:Xenopus Proteins
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C491683:DACT1 protein, human; C000606586:DVL1 protein, Xenopus; C000606581:DVL2 protein, human; D000072261:Dishevelled Proteins; D005452:Fluoresceins; D005456:Fluorescent Dyes; D007211:Indoles; D009687:Nuclear Proteins; D010750:Phosphoproteins; D034741:RNA, Small Interfering; D012235:Rhodamines; D051153:Wnt Proteins; D029867:Xenopus Proteins; C007293:DAPI; D008156:Luciferases