title: Regulation of the tumour suppressor Fbw7α by PKC-dependent phosphorylation and cancer-associated mutations.
abstract: Fbw7 (F-box WD40 protein 7) is a major tumour suppressor, which mediates the degradation of several potent oncogenes. PKC (protein kinase C) comprises a serine/threonine kinase family that can promote transformation when dysregulated. In the present study, we investigated the relationship between Fbw7 and PKC. Multiple members of the PKC superfamily interact with the substrate-binding domain of Fbw7. However, we find no evidence for Fbw7-mediated degradation of PKC. Instead, we demonstrate that Fbw7 is a novel substrate for PKC. Two residues within the isoform-specific N-terminus of Fbw7α are phosphorylated in a PKC-dependent manner, both in vitro and in mammalian cells (Ser¹⁰ and Ser¹⁸). Mutational analyses reveal that phosphorylation of Fbw7α at Ser10 can regulate its nuclear localization. Cancer-associated mutations in nearby residues (K11R and the addition of a proline residue at position 16) influence Fbw7α localization in a comparable manner, suggesting that mislocalization of this protein may be of pathological significance. Together these results provide evidence for both physical and functional interactions between the PKC and Fbw7 families, and yield insights into the isoform-specific regulation of Fbw7α.
authors.affiliation: London Research Institute, Cancer Research UK, UK.
authors.forename: Joanne
authors.initials: J
authors.lastname: Durgan
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Parker
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D019556:COS Cells; D020134:Catalytic Domain; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D002522:Chlorocebus aethiops; D044783:F-Box Proteins / Q000235:genetics* / Q000378:metabolism; D000073979:F-Box-WD Repeat-Containing Protein 7; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009154:Mutation; D009369:Neoplasms / Q000235:genetics / Q000473:pathology; D010766:Phosphorylation; D011485:Protein Binding; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D011493:Protein Kinase C / Q000235:genetics* / Q000378:metabolism; D034622:RNA Interference; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D020798:Two-Hybrid System Techniques; D044767:Ubiquitin-Protein Ligases / Q000235:genetics* / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; D044783:F-Box Proteins; D000073979:F-Box-WD Repeat-Containing Protein 7; C513273:FBXW7 protein, human; D020033:Protein Isoforms; D049452:Green Fluorescent Proteins; D012694:Serine; D044767:Ubiquitin-Protein Ligases; D011493:Protein Kinase C