title: Tissue specificity of a human mitochondrial disease: differentiation-enhanced mis-splicing of the Fe-S scaffold gene ISCU renders patient cells more sensitive to oxidative stress in ISCU myopathy.
abstract: BACKGROUND
  ISCU myopathy is a disease caused by muscle-specific deficiency of the Fe-S cluster scaffold protein ISCU.
  
  
  RESULTS
  MyoD expression enhanced ISCU mRNA mis-splicing, and oxidative stress exacerbated ISCU depletion in patient cells.
  
  
  CONCLUSIONS
  ISCU protein deficiency in patients results from muscle-specific mis-splicing as well as oxidative stress.
  
  
  CONCLUSIONS
  Oxidative stress negatively influences the mammalian Fe-S cluster assembly machinery by destabilization of ISCU. Iron-sulfur (Fe-S) cluster cofactors are formed on the scaffold protein ISCU. ISCU myopathy is a disease caused by an intronic mutation that leads to abnormally spliced ISCU mRNA. We found that two predominant mis-spliced ISCU mRNAs produce a truncated and short-lived ISCU protein product in multiple patient cell types. Expression of the muscle-specific transcription factor MyoD further diminished normal splicing of ISCU mRNA in patient myoblasts, demonstrating that the process of muscle differentiation enhances the loss of normal ISCU mRNA splicing. ISCU protein was nearly undetectable in patient skeletal muscle, but was higher in patient myoblasts, fibroblasts, and lymphoblasts. We next treated patient cells with pro-oxidants to mimic the oxidative stress associated with muscle activity. Brief hydrogen peroxide treatment or incubation in an enriched oxygen atmosphere led to a marked further reduction of ISCU protein levels, which could be prevented by pretreatment with the antioxidant ascorbate. Thus, we conclude that skeletal muscle differentiation of patient cells causes a higher degree of abnormal ISCU splicing and that oxidative stress resulting from skeletal muscle work destabilizes the small amounts of normal ISCU protein generated in patient skeletal muscles.
authors.affiliation: Department of Biochemistry, Molecular and Cellular Biology, Georgetown University Medical Center, Washington, DC 20057, USA.
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Crooks
authors.forename: Suh Young
authors.initials: SY
authors.lastname: Jeong
authors.forename: Wing-Hang
authors.initials: WH
authors.lastname: Tong
authors.forename: Manik C
authors.initials: MC
authors.lastname: Ghosh
authors.forename: Hayden
authors.initials: H
authors.lastname: Olivierre
authors.forename: Ronald G
authors.initials: RG
authors.lastname: Haller
authors.forename: Tracey A
authors.initials: TA
authors.lastname: Rouault
mesh_terms: D000328:Adult; D000368:Aged; D000818:Animals; D002454:Cell Differentiation; D005260:Female; D006801:Humans; D007506:Iron-Sulfur Proteins / Q000235:genetics* / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008875:Middle Aged; D028361:Mitochondrial Diseases / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D018482:Muscle, Skeletal / Q000166:cytology* / Q000378:metabolism; D017570:MyoD Protein / Q000235:genetics / Q000378:metabolism; D009928:Organ Specificity; D018384:Oxidative Stress; D012326:RNA Splicing; D055815:Young Adult
chemical_list: C506160:ISCU protein, human; D007506:Iron-Sulfur Proteins; C523690:IscU protein, mouse; D017570:MyoD Protein