Phosphorylation-independent repression of Yorkie in Fat-Hippo signaling

Dev Biol. 2009 Nov 1;335(1):188-97. doi: 10.1016/j.ydbio.2009.08.026. Epub 2009 Sep 3.

Abstract

The Fat-Hippo signaling pathway plays an important role in the regulation of normal organ growth during development, and in pathological growth during cancer. Fat-Hippo signaling controls growth through a transcriptional co-activator protein, Yorkie. A Fat-Hippo pathway has been described in which Yorkie is repressed by phosphorylation, mediated directly by the kinase Warts and indirectly by upstream tumor suppressors that promote Warts kinase activity. We present here evidence for an alternate pathway in which Yorkie activity is repressed by direct physical association with three other pathway components: Expanded, Hippo, and Warts. Each of these Yorkie repressors contains one or more PPXY sequence motifs, and associates with Yorkie via binding of these PPXY motifs to WW domains of Yorkie. This direct binding inhibits Yorkie activity independently from effects on Yorkie phosphorylation, and does so both in vivo and in cultured cell assays. These results emphasize the importance of the relative levels of Yorkie and its upstream tumor suppressors to Yorkie regulation, and suggest a dual repression model, in which upstream tumor suppressors can regulate Yorkie activity both by promoting Yorkie phosphorylation and by direct binding.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Genetically Modified
  • Cell Adhesion Molecules / genetics
  • Cell Adhesion Molecules / metabolism*
  • Drosophila Proteins / genetics
  • Drosophila Proteins / metabolism*
  • Drosophila melanogaster / anatomy & histology
  • Drosophila melanogaster / embryology
  • Drosophila melanogaster / genetics
  • Gene Expression Regulation, Developmental*
  • Intracellular Signaling Peptides and Proteins / genetics
  • Intracellular Signaling Peptides and Proteins / metabolism*
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • Phosphorylation
  • Protein Kinases / genetics
  • Protein Kinases / metabolism
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism*
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Signal Transduction / physiology*
  • Trans-Activators / genetics
  • Trans-Activators / metabolism*

Substances

  • Cell Adhesion Molecules
  • Drosophila Proteins
  • Intracellular Signaling Peptides and Proteins
  • Membrane Proteins
  • Nuclear Proteins
  • Recombinant Fusion Proteins
  • Trans-Activators
  • Yki protein, Drosophila
  • ex protein, Drosophila
  • ft protein, Drosophila
  • Protein Kinases
  • wts protein, Drosophila
  • Protein-Serine-Threonine Kinases
  • hpo protein, Drosophila