Protein instability and functional defects caused by mutations of dihydro-orotate dehydrogenase in Miller syndrome patients.

Abstract

Miller syndrome is a recessive inherited disorder characterized by postaxial acrofacial dysostosis. It is caused by dysfunction of the DHODH (dihydroorotate dehydrogenase) gene, which encodes a key enzyme in the pyrimidine de novo biosynthesis pathway and is localized at mitochondria intermembrane space. We investigated the consequence of three missense mutations, G202A, R346W and R135C of DHODH, which were previously identified in patients with Miller syndrome. First, we established HeLa cell lines stably expressing DHODH with Miller syndrome-causative mutations: G202A, R346W and R135C. These three mutant proteins retained the proper mitochondrial localization based on immunohistochemistry and mitochondrial subfractionation studies. The G202A, R346W DHODH proteins showed reduced protein stability. On the other hand, the third one R135C, in which the mutation lies at the ubiquinone-binding site, was stable but possessed no enzymatic activity. In conclusion, the G202A and R346W mutation causes deficient protein stability, and the R135C mutation does not affect stability but impairs the substrate-induced enzymatic activity, suggesting that impairment of DHODH activity is linked to the Miller syndrome phenotype.

• Authors: JingXian Fang, Takeshi Uchiumi, Mikako Yagi, Shinya Matsumoto, Rie Amamoto, Toshiro Saito, Shinya Takazaki, Tomotake Kanki, Haruyoshi Yamaza, Kazuaki Nonaka, Dongchon Kang
• Journal: Bioscience reports (Biosci Rep) Vol. 32 Issue 6 Pg. 631-9 (Dec 2012) ISSN: 1573-4935 [Electronic] England
• PMID: 22967083 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Dihydroorotate Dehydrogenase
• Ubiquinone
• Oxidoreductases Acting on CH-CH Group Donors
• Succinate Dehydrogenase
• Electron Transport Complex III

Topics

• Abnormalities, Multiple (enzymology, genetics, metabolism)
• Dihydroorotate Dehydrogenase
• Electron Transport Complex III (metabolism)
• HeLa Cells
• Humans
• Limb Deformities, Congenital (enzymology, genetics, metabolism)
• Mandibulofacial Dysostosis (enzymology, genetics, metabolism)
• Micrognathism (enzymology, genetics, metabolism)
• Mitochondria (enzymology, metabolism)
• Mutation, Missense
• Oxidoreductases Acting on CH-CH Group Donors (analysis, genetics, metabolism)
• Protein Stability
• Succinate Dehydrogenase (metabolism)
• Ubiquinone (metabolism)