Vertebrate primary cilium is a Hedgehog signaling center but the extent of its involvement in other signaling systems is less well understood. This report delineates a mechanism by which fibroblast growth factor (FGF) controls primary cilia. Employing proteomic approaches to characterize proteins associated with the FGF-receptor, FGFR3, we identified the serine/threonine kinase intestinal cell kinase (ICK) as an FGFR interactor. ICK is involved in ciliogenesis and participates in control of ciliary length. FGF signaling partially abolished ICK's kinase activity, through FGFR-mediated ICK phosphorylation at conserved residue Tyr15, which interfered with optimal ATP binding. Activation of the FGF signaling pathway affected both primary cilia length and function in a manner consistent with cilia effects caused by inhibition of ICK activity. Moreover, knockdown and knockout of ICK rescued the FGF-mediated effect on cilia. We provide conclusive evidence that FGF signaling controls cilia via interaction with ICK.

• Keywords
• FGFR, ICK, cilia length, fibroblast growth factor, intestinal cell kinase,
• MeSH
• NIH 3T3 Cells MeSH
• Cilia metabolism   MeSH
• CRISPR-Cas Systems MeSH
• Fibroblast Growth Factors metabolism   MeSH
• Phosphorylation MeSH
• HEK293 Cells MeSH
• Protein Interaction Domains and Motifs MeSH
• Humans MeSH
• Models, Animal MeSH
• Mice, Knockout MeSH
• Mice MeSH
• Protein Serine-Threonine Kinases genetics   metabolism   MeSH
• Hedgehog Proteins metabolism   MeSH
• Proteomics MeSH
• Receptor, Fibroblast Growth Factor, Type 1 metabolism   MeSH
• Receptor, Fibroblast Growth Factor, Type 3 genetics   metabolism   MeSH
• Receptor, Fibroblast Growth Factor, Type 4 metabolism   MeSH
• Receptors, Fibroblast Growth Factor genetics   metabolism   MeSH
• Signal Transduction MeSH
• Molecular Docking Simulation MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, N.I.H., Extramural MeSH
• Names of Substances
• CILK1 protein, human MeSH Browser
• Cilk1 protein, mouse MeSH Browser
• FGFR1 protein, human MeSH Browser
• FGFR3 protein, human MeSH Browser
• FGFR4 protein, human MeSH Browser
• Fibroblast Growth Factors MeSH
• Protein Serine-Threonine Kinases MeSH
• Hedgehog Proteins MeSH
• Receptor, Fibroblast Growth Factor, Type 1 MeSH
• Receptor, Fibroblast Growth Factor, Type 3 MeSH
• Receptor, Fibroblast Growth Factor, Type 4 MeSH
• Receptors, Fibroblast Growth Factor MeSH

Cilia project from almost every cell integrating extracellular cues with signaling pathways. Constitutive activation of FGFR3 signaling produces the skeletal disorders achondroplasia (ACH) and thanatophoric dysplasia (TD), but many of the molecular mechanisms underlying these phenotypes remain unresolved. Here, we report in vivo evidence for significantly shortened primary cilia in ACH and TD cartilage growth plates. Using in vivo and in vitro methodologies, our data demonstrate that transient versus sustained activation of FGF signaling correlated with different cilia consequences. Transient FGF pathway activation elongated cilia, while sustained activity shortened cilia. FGF signaling extended primary cilia via ERK MAP kinase and mTORC2 signaling, but not through mTORC1. Employing a GFP-tagged IFT20 construct to measure intraflagellar (IFT) speed in cilia, we showed that FGF signaling affected IFT velocities, as well as modulating cilia-based Hedgehog signaling. Our data integrate primary cilia into canonical FGF signal transduction and uncover a FGF-cilia pathway that needs consideration when elucidating the mechanisms of physiological and pathological FGFR function, or in the development of FGFR therapeutics.

• MeSH
• Achondroplasia genetics   physiopathology   MeSH
• NIH 3T3 Cells MeSH
• Chondrocytes metabolism   MeSH
• Cartilage metabolism   MeSH
• Cilia pathology   physiology   MeSH
• Ciliopathies genetics   physiopathology   MeSH
• Phenotype MeSH
• Fibroblast Growth Factors metabolism   MeSH
• Humans MeSH
• Mice MeSH
• Primary Cell Culture MeSH
• Receptor, Fibroblast Growth Factor, Type 3 genetics   metabolism   MeSH
• Growth Plate metabolism   MeSH
• Signal Transduction physiology   MeSH
• Thanatophoric Dysplasia genetics   physiopathology   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, N.I.H., Extramural MeSH
• Names of Substances
• FGFR3 protein, human MeSH Browser
• Fibroblast Growth Factors MeSH
• Receptor, Fibroblast Growth Factor, Type 3 MeSH

Many tyrosine kinase inhibitors (TKIs) have failed to reach human use due to insufficient activity in clinical trials. However, the failed TKIs may still benefit patients if their other kinase targets are identified by providing treatment focused on syndromes driven by these kinases. Here, we searched for novel targets of AZD1480, an inhibitor of JAK2 kinase that recently failed phase two cancer clinical trials due to a lack of activity. Twenty seven human receptor tyrosine kinases (RTKs) and 153 of their disease-associated mutants were in-cell profiled for activity in the presence of AZD1480 using a newly developed RTK plasmid library. We demonstrate that AZD1480 inhibits ALK, LTK, FGFR1-3, RET and TRKA-C kinases and uncover a physical basis of this specificity. The RTK activity profiling described here facilitates inhibitor repurposing by enabling rapid and efficient identification of novel TKI targets in cells.

• Keywords
• AZD1480, drug repurposing, in-cell profiling, inhibitor, receptor tyrosine kinase,
• Publication type
• Journal Article MeSH