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

Area of Science:

• Genetics
• Molecular Biology
• Cell Biology

Background:

• McKusick-Kaufman syndrome (MKKS) and Bardet-Biedl syndrome (BBS) are genetic disorders caused by mutations in the MKKS gene.
• The precise molecular mechanisms underlying MKKS/BBS pathogenesis remain largely unknown.

Purpose of the Study:

• To elucidate the cellular mechanisms by which MKKS mutations lead to disease.
• To investigate the role of protein degradation pathways in MKKS/BBS.

Main Methods:

• Utilized cell biology techniques to study MKKS protein localization and degradation in living cells.
• Employed ubiquitin-proteasome pathway inhibitors and RNA interference to assess the role of CHIP and chaperones.
• Analyzed mutant MKKS protein conformation and aggregation.

Main Results:

• Disease-causing MKKS mutants are rapidly degraded via the ubiquitin-proteasome pathway.
• This degradation is dependent on HSC70 interacting protein (CHIP), a chaperone-dependent ubiquitin ligase.
• Mutant MKKS proteins exhibit abnormal conformations, fail to localize correctly to the centrosome, and form insoluble structures upon proteasome inhibition.
• CHIP and chaperones (HSP70, HSP90) recognize MKKS mutants, and CHIP knockdown partially inhibits degradation.

Conclusions:

• Chaperone-dependent degradation mediated by CHIP is a critical factor in the pathogenesis of MKKS/BBS diseases.
• Abnormal protein conformation and subsequent degradation contribute to the developmental anomalies observed in these syndromes.