Highly specific ubiquitin-competing molecules effectively promote frataxin accumulation and partially rescue the aconitase defect in Friedreich ataxia cells.
Bottom Line: The underlying genetic defect leads to reduced expression of the mitochondrial protein frataxin.By extending our search for effective UCM, we identified a set of new and more potent compounds that more efficiently promote frataxin accumulation.Interestingly, these UCM are not effective on the ubiquitin-resistant frataxin mutant, indicating their specific action on preventing frataxin ubiquitination.
Affiliation: Laboratory of Signal Transduction, Department of Biomedicine and Prevention, University of Rome "Tor Vergata," Via Montpellier 1, Rome 00133, Italy; Fratagene Therapeutics Ltd., 22 Northumberland Rd., Dublin, Ireland.Show MeSH
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Mentions: We finally analyzed the efficacy of our compounds in cells derived from FRDA patients. Lymphoblast cell lines derived from two different patients, FRDA 798 and FRDA 214 were cultured for 5 days in the presence of 10 μM of UCM53 or UCM108, the two most promising compounds. UCM71 could not be evaluated because of its toxicity over a long-term treatment (Fig. S1). Frataxin levels were quantified by western blot analysis on whole cell extracts. Importantly, we could observe a significant accumulation of mature frataxin when cells are cultured in the presence of UCM53 or UCM108, compared to cells treated with vehicle alone (control), or UCM72 (Figs. 6A and B). Frataxin levels in treated cells derived from patients are also compared to the levels observed in cells derived from unaffected carrier siblings (FRDA 241 and FRDA 215). These UCM are also more effective than the previously described compounds (Rufini et al., 2011). Indeed, at the concentration of 10 μM that is efficacious for the new UCM, the previously described compound does not show a significant effect (Fig. S2). Moreover, to validate a functional recovery of frataxin levels, rescue of cellular aconitases activity was evaluated in FRDA cells upon treatment with UCM. A significant increase in aconitases activity was observed in patient-derived lymphoblast cell line FRDA 214 after treatment with UCM108 for 5 days (Fig. 6C). Aconitases activity in cells derived from an unaffected carrier sibling (FRDA 215) is also shown for comparison. Thus, importantly, these data indicate that treatment with UCM allows accumulation of a functional form of mature frataxin with consequent reactivation of ISC biogenesis.
Affiliation: Laboratory of Signal Transduction, Department of Biomedicine and Prevention, University of Rome "Tor Vergata," Via Montpellier 1, Rome 00133, Italy; Fratagene Therapeutics Ltd., 22 Northumberland Rd., Dublin, Ireland.