Combined in silico/in vitro approaches for identifying modulators of the activity of the p.Tyr110Cys Carnitine O-Acetyltransferase (CRAT) variant associated to an early onset case of Leigh syndrome.

Carnitine O-acetyltransferase (CRAT) is a crucial enzyme involved in mitochondrial energy metabolism. Alterations in CRAT activity have emerged as significant contributors to the pathogenesis of Leigh syndrome and related mitochondrial disorders. In this study we employed an integrated approach combining in silico docking analysis and virtual screening of chemical libraries with subsequent in vitro validation to identify small molecule modulators of the activity of the wild type (WT) CRAT and the p.Tyr110Cys (Y110C) variant associated to an early onset case of Leigh syndrome. Through 3D molecular modeling, docking simulations, and virtual screening of chemical libraries, potential CRAT modulators were prioritized based on their predicted binding affinities and interactions with the 3D models of the WT-CRAT and of the p.Tyr110Cys-CRAT mutant. The performed in silico analyses were validated through in vitro assays on the purified recombinant CRAT proteins and cell-lysates from control fibroblasts and the fibroblasts of a patient with genetic diagnosis of CRAT-deficiency, carrying the compound heterozygous missense variants in the CRAT gene, namely p.Tyr110Cys and p.Val569Met. Based on the above screening by applying the indicated filtering strategy and mentioned criteria, 3 commercially available approved drugs (also known for their possible interactions with mitochondria) namely glimepiride, artemisinin and dorzolamide, as well as suramin (already known for its ability to interact with mitochondrial proteins) were tested in in vitro assays. We found that suramin (1-1000 μM) dose-dependently inhibited the activity of both WT-CRAT and p.Tyr110Cys_CRAT variant. Artemisinin (0.1-200 μM) dose-dependently stimulated the activity of the recombinant p.Tyr110Cys CRAT mutant, whereas glimepiride and dorzolamide did not change the activity of these proteins towards acetyl-CoA. This study demonstrates the effectiveness of this combined approach in identifying novel compounds for modulating CRAT enzyme activity, providing valuable insights for potential therapeutic interventions targeting CRAT-related disorders.