Complex I assembly function and fatty acid oxidation enzyme activity of ACAD9 both contribute to disease severity in ACAD9 deficiency.
Schiff MDepartment of Pediatrics, University of Pittsburgh School of Medicine, University of Pittsburgh, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, PA 15224, USA Reference Center for Inborn Errors of Metabolism, Hôpital Robert Debré, APHP, INSERM U1141 and Université Paris-Diderot, Sorbonne Paris Cité, Paris, France manuel.schiff@rdb.aphp.fr vockleyg@upmc.edu.
Haberberger BInstitute of Human Genetics, Technische Universität München, Munich, Germany Institute of Human Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany.
Xia CDepartment of Biochemistry, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
Mohsen AWDepartment of Pediatrics, University of Pittsburgh School of Medicine, University of Pittsburgh, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, PA 15224, USA.
Goetzman ESDepartment of Pediatrics, University of Pittsburgh School of Medicine, University of Pittsburgh, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, PA 15224, USA.
Wang YDepartment of Pediatrics, University of Pittsburgh School of Medicine, University of Pittsburgh, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, PA 15224, USA.
Uppala RDepartment of Pediatrics, University of Pittsburgh School of Medicine, University of Pittsburgh, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, PA 15224, USA.
Zhang YDepartment of Pediatrics, University of Pittsburgh School of Medicine, University of Pittsburgh, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, PA 15224, USA.
Karunanidhi ADepartment of Pediatrics, University of Pittsburgh School of Medicine, University of Pittsburgh, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, PA 15224, USA.
Prabhu DDepartment of Pediatrics, University of Pittsburgh School of Medicine, University of Pittsburgh, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, PA 15224, USA.
Alharbi HDepartment of Pediatrics, University of Pittsburgh School of Medicine, University of Pittsburgh, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, PA 15224, USA.
Prochownik EVDepartment of Pediatrics, University of Pittsburgh School of Medicine, University of Pittsburgh, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, PA 15224, USA.
Haack TInstitute of Human Genetics, Technische Universität München, Munich, Germany Institute of Human Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany.
Häberle JDivision of Metabolism, University Children's Hospital Zurich, Zurich, Switzerland.
Munnich AInstitut Imagine and INSERM U781, Sorbonne Paris Cité, Hôpital Necker-Enfants Malades, APHP, Université Paris-Descartes, Paris, France.
Rötig AInstitut Imagine and INSERM U781, Sorbonne Paris Cité, Hôpital Necker-Enfants Malades, APHP, Université Paris-Descartes, Paris, France.
Taylor RWWellcome Trust Centre for Mitochondrial Research, The Medical School, Newcastle University, Newcastle upon Tyne, UK and.
Nicholls RDDepartment of Pediatrics, University of Pittsburgh School of Medicine, University of Pittsburgh, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, PA 15224, USA Department of Human Genetics, University of Pittsburgh, Pittsburgh, PA 15224, USA.
Kim JJDepartment of Biochemistry, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
Prokisch HInstitute of Human Genetics, Technische Universität München, Munich, Germany Institute of Human Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany.
Vockley JDepartment of Pediatrics, University of Pittsburgh School of Medicine, University of Pittsburgh, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, PA 15224, USA Department of Human Genetics, University of Pittsburgh, Pittsburgh, PA 15224, USA manuel.schiff@rdb.aphp.fr vockleyg@upmc.edu.
English
Acyl-CoA dehydrogenase 9 (ACAD9) is an assembly factor for mitochondrial respiratory chain Complex I (CI), and ACAD9 mutations are recognized as a frequent cause of CI deficiency. ACAD9 also retains enzyme ACAD activity for long-chain fatty acids in vitro, but the biological relevance of this function remains controversial partly because of the tissue specificity of ACAD9 expression: high in liver and neurons and minimal in skin fibroblasts. In this study, we hypothesized that this enzymatic ACAD activity is required for full fatty acid oxidation capacity in cells expressing high levels of ACAD9 and that loss of this function is important in determining phenotype in ACAD9-deficient patients. First, we confirmed that HEK293 cells express ACAD9 abundantly. Then, we showed that ACAD9 knockout in HEK293 cells affected long-chain fatty acid oxidation along with Cl, both of which were rescued by wild type ACAD9. Further, we evaluated whether the loss of ACAD9 enzymatic fatty acid oxidation affects clinical severity in patients with ACAD9 mutations. The effects on ACAD activity of 16 ACAD9 mutations identified in 24 patients were evaluated using a prokaryotic expression system. We showed that there was a significant inverse correlation between residual enzyme ACAD activity and phenotypic severity of ACAD9-deficient patients. These results provide evidence that in cells where it is strongly expressed, ACAD9 plays a physiological role in fatty acid oxidation, which contributes to the severity of the phenotype in ACAD9-deficient patients. Accordingly, treatment of ACAD9 patients should aim at counteracting both CI and fatty acid oxidation dysfunctions.