Biochemical Characterization of the Drosophila Wingless Signaling Pathway Based on RNA Interference
- 1 March 2004
- journal article
- Published by Informa UK Limited in Molecular and Cellular Biology
- Vol. 24 (5), 2012-24
- https://doi.org/10.1128/mcb.24.5.2012-2024.2004
Abstract
Regulation of Armadillo (Arm) protein levels through ubiquitin-mediated degradation plays a central role in the Wingless (Wg) signaling. Although zeste-white3 (Zw3)-mediated Arm phosphorylation has been implicated in its degradation, we have recently shown that casein kinase Ialpha (CKIalpha) also phosphorylates Arm and induces its degradation. However, it remains unclear how CKIalpha and Zw3, as well as other components of the Arm degradation complex, regulate Arm phosphorylation in response to Wg. In particular, whether Wg signaling suppresses CKIalpha- or Zw3-mediated Arm phosphorylation in vivo is unknown. To clarify these issues, we performed a series of RNA interference (RNAi)-based analyses in Drosophila S2R+ cells by using antibodies that specifically recognize Arm phosphorylated at different serine residues. These analyses revealed that Arm phosphorylation at serine-56 and at threonine-52, serine-48, and serine-44, is mediated by CKIalpha and Zw3, respectively, and that Zw3-directed Arm phosphorylation requires CKIalpha-mediated priming phosphorylation. Daxin stimulates Zw3- but not CKIalpha-mediated Arm phosphorylation. Wg suppresses Zw3- but not CKIalpha-mediated Arm phosphorylation, indicating that a vital regulatory step in Wg signaling is Zw3-mediated Arm phosphorylation. In addition, further RNAi-based analyses of the other aspects of the Wg pathway clarified that Wg-induced Dishevelled phosphorylation is due to CKIalpha and that presenilin and protein kinase A play little part in the regulation of Arm protein levels in Drosophila tissue culture cells.Keywords
This publication has 52 references indexed in Scilit:
- A Wnt-Wnt SituationDevelopmental Cell, 2003
- The Mechanism of γ-Secretase Activities through High Molecular Weight Complex Formation of Presenilins Is Conserved inDrosophila melanogaster and MammalsJournal of Biological Chemistry, 2002
- Presenilin Couples the Paired Phosphorylation of β-Catenin Independent of AxinCell, 2002
- Wnt signal transduction: kinase cogs in a nano-machine?Trends in Biochemical Sciences, 2002
- Glycogen Synthase Kinase-3β Mutagenesis Identifies a Common Binding Domain for GBP and AxinPublished by Elsevier BV ,2002
- Physiological regulation of β-catenin stability by Tcf3 and CK1ϵ The Journal of cell biology, 2001
- Synergistic Activation of the Wnt Signaling Pathway by Dvl and Casein Kinase IεJournal of Biological Chemistry, 2001
- Wnt-induced dephosphorylation of Axin releases beta -catenin from the Axin complexGenes & Development, 1999
- MECHANISMS OF WNT SIGNALING IN DEVELOPMENTAnnual Review of Cell and Developmental Biology, 1998
- Biological activity of soluble wingless protein in cultured Drosophila imaginal disc cellsNature, 1994