pVHL acts as an adaptor to promote the inhibitory phosphorylation of the NF-kappaB agonist Card9 by CK2.

The VHL tumor suppressor protein (pVHL) is part of an E3 ubiquitin ligase that targets HIF for destruction. pVHL-defective renal carcinoma cells exhibit increased NF-kappaB activity but the mechanism is unclear. NF-kappaB affects tumorigenesis and therapeutic resistance in some settings. We found that pVHL associates with the NF-kappaB agonist Card9 ...
but does not target Card9 for destruction. Instead, pVHL serves as an adaptor that promotes the phosphorylation of the Card9 C terminus by CK2. Elimination of these sites markedly enhanced Card9's ability to activate NF-kappaB in VHL(+/+) cells, and Card9 siRNA normalized NF-kappaB activity in VHL(-/-) cells and restored their sensitivity to cytokine-induced apoptosis. Furthermore, downregulation of Card9 in VHL(-/-) cancer cells reduced their tumorigenic potential. Therefore pVHL can serve as an adaptor for both a ubiquitin conjugating enzyme and a kinase. The latter activity, which promotes Card9 phosphorylation, links pVHL to control of NF-kappaB activity and tumorigenesis.
Mesh Terms:
Amino Acid Sequence, Animals, CARD Signaling Adaptor Proteins, Carcinoma, Renal Cell, Casein Kinase II, HeLa Cells, Humans, Kidney Neoplasms, Liver, Mice, Mice, Nude, Molecular Sequence Data, NF-kappa B, Neoplasm Transplantation, PC12 Cells, Phosphorylation, RNA, Small Interfering, Rats, Recombinant Fusion Proteins, Tumor Necrosis Factor-alpha, Von Hippel-Lindau Tumor Suppressor Protein
Mol. Cell
Date: Oct. 12, 2007
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