The WW domain protein Kibra acts upstream of Hippo in Drosophila.
The conserved Hippo kinase pathway plays a pivotal role in organ size control and tumor suppression by restricting proliferation and promoting apoptosis. Whereas the function of the core kinase cascade, consisting of the serine/threonine kinases Hippo and Warts, in phosphorylating and thereby inactivating the transcriptional coactivator Yorkie is well established, much less is known about the upstream events that regulate Hippo signaling activity. The FERM domain proteins Expanded and Merlin appear to represent two different signaling branches that feed into the Hippo pathway. Signaling by the atypical cadherin Fat may act via Expanded, but how Merlin is regulated has remained elusive. Here, we show that the WW domain protein Kibra is a Hippo signaling component upstream of Hippo and Merlin. Kibra acts synergistically with Expanded, and it physically interacts with Merlin. Thus, Kibra predominantly acts in the Merlin branch upstream of the core kinase cascade to regulate Hippo signaling.
Institute of Molecular Systems Biology, ETH Zürich, Wolfgang-Pauli-Strasse 16, 8093 Zürich, Switzerland.
Roland
R
Baumgartner
Ingrid
I
Poernbacher
Nathalie
N
Buser
Ernst
E
Hafen
Hugo
H
Stocker
D000818:Animals; D030801:Animals, Genetically Modified; D017209:Apoptosis; D002452:Cell Count; D002460:Cell Line; D004330:Drosophila / Q000235:genetics / Q000254:growth & development* / Q000502:physiology*; D029721:Drosophila Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D004843:Epistasis, Genetic; D018507:Gene Expression Regulation, Developmental; D017344:Genes, Insect; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000502:physiology*; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology; D009154:Mutation; D025581:Neurofibromin 2 / Q000235:genetics / Q000502:physiology; D009687:Nuclear Proteins / Q000235:genetics / Q000502:physiology; D009929:Organ Size; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000502:physiology*; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D015534:Trans-Activators / Q000235:genetics / Q000502:physiology; D025521:Tumor Suppressor Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D000091102:YAP-Signaling Proteins; D000099317:Hippo Kinases
D029721:Drosophila Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D025581:Neurofibromin 2; D009687:Nuclear Proteins; D017346:Protein Serine-Threonine Kinases; D015534:Trans-Activators; D025521:Tumor Suppressor Proteins; D000091102:YAP-Signaling Proteins; C503814:Yki protein, Drosophila; C085090:ex protein, Drosophila; C548168:kibra protein, Drosophila; C099885:merlin, Drosophila; C499474:hpo protein, Drosophila; D000099317:Hippo Kinases