title: An unconventional nuclear localization motif is crucial for function of the Drosophila Wnt/wingless antagonist Naked cuticle.
abstract: Wnt/beta-catenin signals orchestrate cell fate and behavior throughout the animal kingdom. Aberrant Wnt signaling impacts nearly the entire spectrum of human disease, including birth defects, cancer, and osteoporosis. If Wnt signaling is to be effectively manipulated for therapeutic advantage, we first must understand how Wnt signals are normally controlled. Naked cuticle (Nkd) is a novel and evolutionarily conserved inducible antagonist of Wnt/beta-catenin signaling that is crucial for segmentation in the model genetic organism, the fruit fly Drosophila melanogaster. Nkd can bind and inhibit the Wnt signal transducer Dishevelled (Dsh), but the mechanism by which Nkd limits Wnt signaling in the fly embryo is not understood. Here we show that nkd mutants exhibit elevated levels of the beta-catenin homolog Armadillo but no alteration in Dsh abundance or distribution. In the fly embryo, Nkd and Dsh are predominantly cytoplasmic, although a recent report suggests that vertebrate Dsh requires nuclear localization for activity in gain-of-function assays. While Dsh-binding regions of Nkd contribute to its activity, we identify a conserved 30-amino-acid motif, separable from Dsh-binding regions, that is essential for Nkd function and nuclear localization. Replacement of the 30-aa motif with a conventional nuclear localization sequence rescued a small fraction of nkd mutant animals to adulthood. Our studies suggest that Nkd targets Dsh-dependent signal transduction steps in both cytoplasmic and nuclear compartments of cells receiving the Wnt signal.
authors.affiliation: Department of Pathology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9072, USA.
authors.forename: Sharon
authors.initials: S
authors.lastname: Waldrop
authors.forename: Chih-Chiang
authors.initials: CC
authors.lastname: Chan
authors.forename: Tolga
authors.initials: T
authors.lastname: Cagatay
authors.forename: Shu
authors.initials: S
authors.lastname: Zhang
authors.forename: Raphaël
authors.initials: R
authors.lastname: Rousset
authors.forename: Judy
authors.initials: J
authors.lastname: Mack
authors.forename: Wenlin
authors.initials: W
authors.lastname: Zeng
authors.forename: Matt
authors.initials: M
authors.lastname: Fish
authors.forename: Mei
authors.initials: M
authors.lastname: Zhang
authors.forename: Manami
authors.initials: M
authors.lastname: Amanai
authors.forename: Keith A
authors.initials: KA
authors.lastname: Wharton
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology; D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry / Q000378:metabolism; D020816:Amino Acid Motifs / Q000502:physiology; D000595:Amino Acid Sequence; D000818:Animals; D000852:Anopheles / Q000235:genetics; D051186:Armadillo Domain Proteins / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D000072261:Dishevelled Proteins; D004330:Drosophila / Q000196:embryology / Q000235:genetics / Q000378:metabolism*; D029721:Drosophila Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D004625:Embryo, Nonmammalian; D051379:Mice; D008954:Models, Biological; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000502:physiology; D009154:Mutation; D019913:Nuclear Localization Signals / Q000502:physiology*; D010750:Phosphoproteins / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014018:Tissue Distribution; D014157:Transcription Factors / Q000378:metabolism; D051153:Wnt Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051155:Wnt1 Protein; D051176:beta Catenin / Q000378:metabolism
chemical_list: C495305:ARM protein, Drosophila; D048868:Adaptor Proteins, Signal Transducing; D051186:Armadillo Domain Proteins; D000072261:Dishevelled Proteins; D029721:Drosophila Proteins; D050505:Mutant Proteins; D019913:Nuclear Localization Signals; D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; D014157:Transcription Factors; D051153:Wnt Proteins; D051155:Wnt1 Protein; D051176:beta Catenin; C000606588:dsh protein, Drosophila; C405336:nkd protein, Drosophila; C074622:wg protein, Drosophila