title: The von Hippel-Lindau tumor suppressor protein mediates ubiquitination of activated atypical protein kinase C.
abstract: The von Hippel-Lindau tumor-suppressor protein (pVHL) forms a protein complex (VCB-Cul2) with elongin C, elongin B, Cul-2, and Rbx1, which functions as a ubiquitin-protein ligase (E3). The alpha-subunits of the hypoxia-inducible factors have been identified as targets for the VCB-Cul2 ubiquitin ligase. However, a variety of cellular defects caused by the depletion of pVHL cannot be explained solely by the ubiquitin-mediated degradation of hypoxia-inducible factor-alpha. We show here that a member of the atypical protein kinase C (PKC) group, PKClambda, is ubiquitinated by the pVHL-containing E3 enzyme. An active PKClambda mutant is ubiquitinated more extensively than wild-type PKClambda in HEK293 cells, and the ubiquitination is further enhanced by the overexpression of pVHL. The activation of wild-type PKClambda by serum stimulation of cells enhances the ubiquitination of the protein, supporting the notion that active PKClambda is preferentially ubiquitinated by VCB-Cul2 ubiquitin ligase. Furthermore, we show that PKClambda can be ubiquitinated in vitro in a cell-free ubiquitination assay using purified recombinant components including VCB-Cul2. Given the known function of aPKC in the regulation of cell polarity and cell growth, PKClambda may be a target of pVHL in its function as a tumor suppressor.
authors.affiliation: Department of Urology, Kochi Medical School, Kochi 783-8505, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Okuda
authors.forename: K
authors.initials: K
authors.lastname: Saitoh
authors.forename: S
authors.initials: S
authors.lastname: Hirai
authors.forename: K
authors.initials: K
authors.lastname: Iwai
authors.forename: Y
authors.initials: Y
authors.lastname: Takaki
authors.forename: M
authors.initials: M
authors.lastname: Baba
authors.forename: N
authors.initials: N
authors.lastname: Minato
authors.forename: S
authors.initials: S
authors.lastname: Ohno
authors.forename: T
authors.initials: T
authors.lastname: Shuin
mesh_terms: D002460:Cell Line; D003546:Cysteine Endopeptidases / Q000187:drug effects; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004789:Enzyme Activation; D006801:Humans; D006868:Hydrolysis; D007527:Isoenzymes; D008025:Ligases / Q000378:metabolism / Q000502:physiology*; D009097:Multienzyme Complexes / Q000187:drug effects; D046988:Proteasome Endopeptidase Complex; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000378:metabolism / Q000502:physiology*; D025801:Ubiquitin / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases; D051794:Von Hippel-Lindau Tumor Suppressor Protein; D006623:von Hippel-Lindau Disease / Q000378:metabolism; D000099293:Protein Kinase C-lambda
chemical_list: D003546:Cysteine Endopeptidases; D015853:Cysteine Proteinase Inhibitors; D007527:Isoenzymes; D008025:Ligases; D009097:Multienzyme Complexes; D046988:Proteasome Endopeptidase Complex; D011493:Protein Kinase C; D025521:Tumor Suppressor Proteins; D025801:Ubiquitin; D044767:Ubiquitin-Protein Ligases; D051794:Von Hippel-Lindau Tumor Suppressor Protein; D000099293:Protein Kinase C-lambda; C497446:VHL protein, human