Regulation of the protein kinase activity of Shaggy(Zeste-white3) by components of the wingless pathway in Drosophila cells and embryos.
The protein-serine kinase Shaggy(Zeste-white3) (Sgg(Zw3)) is the Drosophila homolog of mammalian glycogen synthase kinase-3 and has been genetically implicated in signal transduction pathways necessary for the establishment of patterning. Sgg(Zw3) is a putative component of the Wingless (Wg) pathway, and epistasis analyses suggest that Sgg(Zw3) function is repressed by Wg signaling. Here, we have investigated the biochemical consequences of Wg signaling with respect to the Sgg(Zw3) protein kinase in two types of Drosophila cell lines and in embryos. Our results demonstrate that Sgg(Zw3) activity is inhibited following exposure of cells to Wg protein and by expression of downstream components of Wg signaling, Drosophila frizzled 2 and dishevelled. Wg-dependent inactivation of Sgg(Zw3) is accompanied by serine phosphorylation. We also show that the level of Sgg(Zw3) activity regulates the stability of Armadillo protein and modulates the level of phosphorylation of D-Axin and Armadillo. Together, these results provide direct biochemical evidence in support of the genetic model of Wg signaling and provide a model for dissecting the molecular interactions between the signaling proteins.
Division of Experimental Therapeutics, Ontario Cancer Institute, and the Department of Medical Biophysics, University of Toronto, Toronto, Ontario M5G 2M9, Canada.
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Ruel
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Stambolic
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Manoukian
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Woodgett
D000818:Animals; D002460:Cell Line; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000196:embryology / Q000235:genetics* / Q000502:physiology*; D004625:Embryo, Nonmammalian / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic; D038362:Glycogen Synthase Kinase 3; D008668:Metallothionein / Q000235:genetics; D011401:Promoter Regions, Genetic; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D015398:Signal Transduction; D014162:Transfection; D051155:Wnt1 Protein
D029721:Drosophila Proteins; D011518:Proto-Oncogene Proteins; D011994:Recombinant Proteins; D012097:Repressor Proteins; D051155:Wnt1 Protein; C074622:wg protein, Drosophila; D008668:Metallothionein; D017346:Protein Serine-Threonine Kinases; C080335:Sgg protein, Drosophila; D038362:Glycogen Synthase Kinase 3