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Elife. 2019 Sep 30;8. pii: e46592. doi: 10.7554/eLife.46592.

Casein kinase 1 family proteins promote Slimb-dependent Expanded degradation.

Author information

Centre for Tumour Biology, Barts Cancer Institute, Queen Mary University of London, London, United Kingdom.
Department of Developmental Biology, Washington University School of Medicine, St. Louis, United States.
Apoptosis and Proliferation Control Laboratory, The Francis Crick Institute, London, United Kingdom.
Proteomics, The Francis Crick Institute, London, United Kingdom.
Contributed equally


Hippo signalling integrates diverse stimuli related to epithelial architecture to regulate tissue growth and cell fate decisions. The Hippo kinase cascade represses the growth-promoting transcription co-activator Yorkie. The FERM protein Expanded is one of the main upstream Hippo signalling regulators in Drosophila as it promotes Hippo kinase signalling and directly inhibits Yorkie. To fulfil its function, Expanded is recruited to the plasma membrane by the polarity protein Crumbs. However, Crumbs-mediated recruitment also promotes Expanded turnover via a phosphodegron-mediated interaction with a Slimb/β-TrCP SCF E3 ligase complex. Here, we show that the Casein Kinase 1 (CKI) family is required for Expanded phosphorylation. CKI expression promotes Expanded phosphorylation and interaction with Slimb/β-TrCP. Conversely, CKI depletion in S2 cells impairs Expanded degradation downstream of Crumbs. In wing imaginal discs, CKI loss leads to elevated Expanded and Crumbs levels. Thus, phospho-dependent Expanded turnover ensures a tight coupling of Hippo pathway activity to epithelial architecture.


D. melanogaster; casein kinase 1; cell biology; developmental biology; expanded; hippo signalling; tissue growth

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