title: Missense mutations in the human SDHB gene increase protein degradation without altering intrinsic enzymatic function.
abstract: Mutations of succinate dehydrogenase subunit B (SDHB) play a crucial role in the pathogenesis of the most aggressive and metastatic pheochromocytomas (PHEOs) and paragangliomas (PGLs). Although a variety of missense mutations in the coding sequence of the SDHB gene have been found in PHEOs and PGLs, it has been unclear whether these mutations impair mRNA expression, protein stability, subcellular localization, or intrinsic protein function. RT-PCR and Western blot analysis of SDHB mRNA and protein expression from SDHB-related PHEOs and PGLs demonstrated intact mRNA expression but significantly reduced protein expression compared to non-SDHB PHEOs and PGLs. A pulse-chase assay of common SDHB missense mutations in transfected HeLa cell lines demonstrated that the loss of SDHB function was due to a reduction in mutant protein half-life, whereas colocalization of SDHB with mitochondria and immunoprecipitation with SDHA demonstrated intact subcellular localization and complex formation. The half-life of the SDHB protein increased after treatment with histone deacetylase inhibitors (HDACis), implicating the protein quality control machinery in the degradation of mutant SDHB protein. These findings provide the first direct mechanism of functional loss resulting from SDHB mutations and suggest that reducing protein degradation with HDACis may serve as a novel therapeutic paradigm for preventing the development of SDHB-related tumors.
authors: Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892-1414, USA.
authors: Chunzhang
authors: C
authors: Yang
authors: Joey C
authors: JC
authors: Matro
authors: Kristin M
authors: KM
authors: Huntoon
authors: Donald Y
authors: DY
authors: Ye
authors: Thanh T
authors: TT
authors: Huynh
authors: Stephanie M J
authors: SM
authors: Fliedner
authors: Jan
authors: J
authors: Breza
authors: Zhengping
authors: Z
authors: Zhuang
authors: Karel
authors: K
authors: Pacak
mesh_terms: D003001:Cloning, Molecular; D004795:Enzyme Stability; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D006367:HeLa Cells; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology; D006801:Humans; D008928:Mitochondria / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D020125:Mutation, Missense; D010235:Paraganglioma / Q000378:metabolism; D010673:Pheochromocytoma / Q000378:metabolism; D011485:Protein Binding; D059748:Proteolysis; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013385:Succinate Dehydrogenase / Q000235:genetics* / Q000378:metabolism*
chemical_list: D056572:Histone Deacetylase Inhibitors; D012333:RNA, Messenger; C108095:SDHB protein, human; D013385:Succinate Dehydrogenase