MKKS is a centrosome-shuttling protein degraded by disease-causing mutations via CHIP-mediated ubiquitination

Mol Biol Cell. 2008 Mar;19(3):899-911. doi: 10.1091/mbc.e07-07-0631. Epub 2007 Dec 19.


McKusick-Kaufman syndrome (MKKS) is a recessively inherited human genetic disease characterized by several developmental anomalies. Mutations in the MKKS gene also cause Bardet-Biedl syndrome (BBS), a genetically heterogeneous disorder with pleiotropic symptoms. However, little is known about how MKKS mutations lead to disease. Here, we show that disease-causing mutants of MKKS are rapidly degraded via the ubiquitin-proteasome pathway in a manner dependent on HSC70 interacting protein (CHIP), a chaperone-dependent ubiquitin ligase. Although wild-type MKKS quickly shuttles between the centrosome and cytosol in living cells, the rapidly degraded mutants often fail to localize to the centrosome. Inhibition of proteasome functions causes MKKS mutants to form insoluble structures at the centrosome. CHIP and partner chaperones, including heat-shock protein (HSP)70/heat-shock cognate 70 and HSP90, strongly recognize MKKS mutants. Modest knockdown of CHIP by RNA interference moderately inhibited the degradation of MKKS mutants. These results indicate that the MKKS mutants have an abnormal conformation and that chaperone-dependent degradation mediated by CHIP is a key feature of MKKS/BBS diseases.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bardet-Biedl Syndrome / genetics*
  • Cell Line
  • Centrosome / metabolism*
  • Cytosol / metabolism
  • Glutamic Acid / genetics
  • Glycine / genetics
  • Group II Chaperonins
  • Humans
  • Mice
  • Microtubules / metabolism
  • Molecular Chaperones / metabolism*
  • Mutant Proteins / metabolism
  • Mutation / genetics*
  • Proteasome Inhibitors
  • Protein Processing, Post-Translational*
  • Protein Structure, Quaternary
  • Protein Transport
  • Solubility
  • Ubiquitin-Protein Ligases / metabolism*
  • Ubiquitination*


  • MKKS protein, human
  • Mkks protein, mouse
  • Molecular Chaperones
  • Mutant Proteins
  • Proteasome Inhibitors
  • Glutamic Acid
  • STUB1 protein, human
  • Ubiquitin-Protein Ligases
  • Group II Chaperonins
  • Glycine