Characterization and pharmacological Modulation of DHTKD1: new therapeutic approach for glutaric aciduria type I

• Applicants: Professor Dr. Stefan Kölker; Dr. Holger Prokisch; Privatdozent Dr. Sven Sauer
• Subject Area: Epidemiology and Medical Biometry/Statistics
• Term: from 2014 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 264597059

Glutaric aciduria type I is an autosomal-recessive defect of the enzyme glutaryl-CoA dehydrogenase (GCDH) in lysine metabolism. Due to the enzymatic defect the neurotoxic metabolites glutaryl-CoA, glutaric acid, and 3-hydroxyglutaric acid accumulate. Untreated patients develop bilateral striatal lesions. Gcdh-deficient (Gcdh-/-) mice show the same biochemical phenotype as patients and develop a neurological phenotype under lysine-enriched diet. 2-Amino-/2-oxoadipic aciduria is another inherited defect in lysine metabolism. Recently, we have identified disease-causing mutations in the protein DHTKD1 (dehydrogenase E1 and transketolase domain containing 1). Half of the patients remains asymptomatic, whereas the other half displays a mild neurological phenotype. All affected individuals are characterized by accumulation of 2-aminoadipate and 2-oxoadipate. DHTKD1 is a subunit of an alternative 2-oxoglutarate-dehydrogenase complex (OGDHc) catalyzing the formation of glutaryl-CoA from 2-oxoadipate and, thereby, being one enzymatic step before GCDH. The lacking or mild phenotype of patients affected with 2-amino- / 2-oxoadipate aciduria suggests that pharmacologic inhibition of DHTKD1 is a promising new therapeutic approach for glutaric aciduria type I. To gain a better understanding of the role of DHTKD1 in cellular metabolism and to evaluate potential risks of the aforementioned therapy, we have created Dhtkd1-/- mice using transcription activator-like effector nucleases technique. After characterization of these mice, they will be crossbred with Gcdh-/- mice. The double knock out-mice will be used to investigate the efficacy of the new therapeutic approach, i.e. reduction of glutaric and 3-hydroxyglutaric acid levels as well as a reduced susceptibility to a lysine-enriched diet. In parallel we will purify and characterize the OGDHc-like complex containing DHTKD1 from prokaryotic and eukaryotic expression systems. The purified protein will be used to establish an enzymatic assay system for inhibitor studies. Using High-Throughput-Drug screen we will identify small molecules / antimetabolites to inhibit DHTKD1. Inhibitory efficacy of these compounds will be studied in vitro using the purified protein and in fibroblasts of glutaric aciduria type I patients as well as in vivo in Gcdh-/- mice.

• DFG Programme: Research Grants