PhD Defense - Molecular insights into the LRPPRC/SLIRP complex and its role in mitochondrial disease

par Louise LAMBERT

vendredi 24 avr. 2026, 13:00 → 15:00 Europe/Paris

Amphi Recherche

(The PhD defense will be in French)

The LRPPRC/SLIRP complex is a key post-transcriptional regulator of mitochondrial DNA (mtDNA) expression. Acting as an mRNA chaperone, this complex promotes the stability and translation of mitochondrial mRNAs by facilitating their polyadenylation and delivery to the mitoribosome. Mutations in LRPPRC are associated with several mitochondrial diseases, primarily affecting the oxidative phosphorylation (OXPHOS) system.
In this thesis, we analyzed in vitro the RNA-binding affinity of wild-type (WT) LRPPRC and three pathogenic variants: A354V, the most frequent mutation responsible for the French-Canadian form of Leigh syndrome, K909del, and R1276_K1300del. Electrophoretic mobility shift assays (EMSAs) were performed using probes corresponding to the ATP6 mRNA and a poly(A) RNA, used to mimic the poly(A) tails of mitochondrial mRNAs. In the absence of SLIRP, all mutants displayed reduced RNA binding, particularly with the poly(A) RNA probe, with the R1276_K1300del mutant showing no detectable binding. In contrast, in the presence of SLIRP, RNA binding of the R1276_K1300del mutant was largely restored on the mATP6 probe. Titration experiments revealed that this mutant required between two and three SLIRP molecules per LRPPRC to reach ~50% of the binding level observed for the WT protein. Single-molecule measurements by acoustic force spectroscopy further demonstrated that the RNA-binding modes of WT and R1276_K1300del LRPPRC/SLIRP complexes were comparable. Additionally, in silico structural predictions indicate that SLIRP binding induces a conformational rearrangement of the mutant protein, bringing it closer to the WT structure.
Taken together, these results demonstrate that all three mutations severely impair the intrinsic RNA-binding capacity of LRPPRC. However, SLIRP can partially restore the function of the R1276_K1300del mutant, suggesting a SLIRP-mediated stabilization of the mutant protein. These findings highlight the essential role of SLIRP in modulating LRPPRC function and open perspectives for potential therapeutic approaches in LRPPRC-related mitochondrial diseases.