Tilokani, L. | Search bioRxiv

bioRxiv2021

Selective and reversible disruption of mitochondrial inner membrane protein complexes by lipophilic cations

Triphenylphosphonium (TPP) derivatives are commonly used to target chemical into mitochondria. We show that alkyl-TPP cause reversible, dose- and hydrophobicity-dependent alterations of mitochondrial morphology and function and a selective decrease of mitochondrial inner membrane proteins including subunits of the respiratory chain complexes, as well as components of the mitochondrial calcium uniporter complex. The treatment with alkyl-TPP resulted in the cleavage of the pro-fusion and cristae organisation regulator Optic atrophy-1. The structural and functional effects of alkyl-TPP were found to be reversible and not merely due to loss of membrane potential. A similar effect was observed with the mitochondria-targeted antioxidant MitoQ.

biochemistry↗

bioRxiv2020

In vivo and in vitro mechanistic characterization of a clinically relevant PolγA mutation

Mutations in POLG, encoding POL{gamma}A, the catalytic subunit of the mitochondrial DNA polymerase, cause a spectrum of disorders characterized by mtDNA instability. However, the molecular pathogenesis of POLG-related diseases is poorly understood and efficient treatments are missing. Here, we generated a POLGA449T/A449T mouse model, which reproduces the most common human recessive mutation of POLG, encoding the A467T change, and dissected the mechanisms underlying pathogenicity. We show that the A449T mutation impairs DNA binding and mtDNA synthesis activities of POL{gamma} in vivo and in vitro. Interestingly, the A467T mutation also strongly impairs interactions with POL{gamma}B, the homodimeric accessory subunit of holo-POL{gamma}. This allows the free POL{gamma}A to become a substrate for LONP1 protease degradation, leading to dramatically reduced levels of POL{gamma}A, which in turn exacerbates the molecular phenotypes of PolgA449T/A449T mice. Importantly, we validated this mechanism for other mutations affecting the interaction between the two POL{gamma} subunits. We suggest that LONP1 dependent degradation of POL{gamma}A can be exploited as a target for the development of future therapies.

genetics↗