title: Direct and indirect control of mitogen-activated protein kinase pathway-associated components, BRAP/IMP E3 ubiquitin ligase and CRAF/RAF1 kinase, by the deubiquitylating enzyme USP15.
abstract: The opposing regulators of ubiquitylation status, E3 ligases and deubiquitylases, are often found to be associated in complexes. Here we report on a novel interaction between the E3 ligase BRAP (also referred to as IMP), a negative regulator of the MAPK scaffold protein KSR, and two closely related deubiquitylases, USP15 and USP4. We map the interaction to the N-terminal DUSP-UBL domain of USP15 and the coiled coil region of BRAP. USP15 as well as USP4 oppose the autoubiquitylation of BRAP, whereas BRAP promotes the ubiquitylation of USP15. Importantly, USP15 but not USP4 depletion destabilizes BRAP by promoting its proteasomal degradation, and BRAP-protein levels can be rescued by reintroducing catalytically active but not inactive mutant USP15. Unexpectedly, USP15 depletion results in a decrease in amplitude of MAPK signaling in response to EGF and PDGF. We provide evidence for a model in which the dominant effect of prolonged USP15 depletion upon signal amplitude is due to a decrease in CRAF levels while allowing for the possibility that USP15 may also function to dampen MAPK signaling through direct stabilization of a negative regulator, the E3 ligase BRAP.
authors.affiliation: Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Crown Street, Liverpool L69 3BX, United Kingdom.
authors.forename: Sebastian D
authors.initials: SD
authors.lastname: Hayes
authors.forename: Han
authors.initials: H
authors.lastname: Liu
authors.forename: Ewan
authors.initials: E
authors.lastname: MacDonald
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Sanderson
authors.forename: Judy M
authors.initials: JM
authors.lastname: Coulson
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Clague
authors.forename: Sylvie
authors.initials: S
authors.lastname: Urbé
mesh_terms: D055162:Biocatalysis / Q000187:drug effects; D002460:Cell Line; D010450:Endopeptidases / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D004795:Enzyme Stability / Q000187:drug effects; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000235:genetics; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D059748:Proteolysis / Q000187:drug effects; D019908:Proto-Oncogene Proteins c-raf / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D020798:Two-Hybrid System Techniques; D043222:Ubiquitin Thiolesterase / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*; D064570:Ubiquitin-Specific Proteases; D054875:Ubiquitination / Q000187:drug effects
chemical_list: D010982:Platelet-Derived Growth Factor; D034741:RNA, Small Interfering; C486203:USP4 protein, human; C111164:BRAP protein, human; D044767:Ubiquitin-Protein Ligases; D019908:Proto-Oncogene Proteins c-raf; D020928:Mitogen-Activated Protein Kinases; D010450:Endopeptidases; C579226:USP15 protein, human; D043222:Ubiquitin Thiolesterase; D064570:Ubiquitin-Specific Proteases; D046988:Proteasome Endopeptidase Complex