Toxic and nutritional factors trigger Leber hereditary optic neuropathy due to a mitochondrial tRNA mutation.

Leber hereditary optic neuropathy is a mitochondrial disease mainly due to pathologic mutations in mitochondrial genes related to the respiratory complex I of the oxidative phosphorylation system. Genetic, physiological, and environmental factors modulate the penetrance of these mutations. We report two patients suffering from this disease and harboring a m.15950G > A mutation in the mitochondrial DNA-encoded gene for the threonine transfer RNA. We also provide evidences supporting the pathogenicity of this mutation.

Mitochondrial DNA pathogenic mutations in multiple symmetric lipomatosis.

The frequency of dermatological manifestations in diseases due to mitochondrial DNA mutations is not well known, although multiple symmetric lipomatosis has been repeatedly associated to mitochondrial DNA mutations. Here, we present a patient suffering from multiple symmetric lipomatosis and other skin signs. We found a new mitochondrial DNA mutation, m.8357T>C, in the tRNALys -coding gene and, using a cybrid approach, confirmed its pathogenicity. A meta-analysis of the dermatological signs of the patient shows that they are not common in patients with confirmed mitochondrial DNA mutations and suggests that, in these cases, lipomatosis is not related to the oxidative phosphorylation dysfunction, but to an alteration of an additional function associated to particular mitochondrial tRNAs.

Oxidative Phosphorylation Dysfunction Modifies the Cell Secretome.

Mitochondrial oxidative phosphorylation disorders are extremely heterogeneous conditions. Their clinical and genetic variability makes the identification of reliable and specific biomarkers very challenging. Until now, only a few studies have focused on the effect of a defective oxidative phosphorylation functioning on the cell's secretome, although it could be a promising approach for the identification and pre-selection of potential circulating biomarkers for mitochondrial diseases. Here, we review the insights obtained from secretome studies with regard to oxidative phosphorylation dysfunction, and the biomarkers that appear, so far, to be promising to identify mitochondrial diseases. We propose two new biomarkers to be taken into account in future diagnostic trials.

ISR pathway contribution to tissue specificity of mitochondrial diseases.

Mitochondrial genetic defects caused by whole-body mutations typically affect different tissues in different ways. Elucidating the molecular determinants that cause certain cell types to be primarily affected has become a critical research target within the field. We propose a differential activation of the integrated stress response as a potential contributor to this tissue specificity.

The structural conformation of the tachykinin domain drives the anti-tumoural activity of an octopus peptide in melanoma BRAFV600E.

BACKGROUND AND PURPOSE: Over past decades, targeted therapies and immunotherapy have improved survival and reduced the morbidity of patients with BRAF-mutated melanoma. However, drug resistance and relapse hinder overall success. Therefore, there is an urgent need for novel compounds with therapeutic efficacy against BRAF-melanoma. This prompted us to investigate the antiproliferative profile of a tachykinin-peptide from the Octopus kaurna, Octpep-1 in melanoma. EXPERIMENTAL APPROACH: We evaluated the cytotoxicity of Octpep-1 by MTT assay. Mechanistic insights on viability and cellular damage caused by Octpep-1 were gained via flow cytometry and bioenergetics. Structural and pharmacological characterization was conducted by molecular modelling, molecular biology, CRISPR/Cas9 technology, high-throughput mRNA and calcium flux analysis. In vivo efficacy was validated in two independent xerograph animal models (mice and zebrafish). KEY RESULTS: Octpep-1 selectively reduced the proliferative capacity of human melanoma BRAFV600E -mutated cells with minimal effects on fibroblasts. In melanoma-treated cells, Octpep-1 increased ROS with unaltered mitochondrial membrane potential and promoted non-mitochondrial and mitochondrial respiration with inefficient ATP coupling. Molecular modelling revealed that the cytotoxicity of Octpep-1 depends upon the α-helix and polyproline conformation in the C-terminal region of the peptide. A truncated form of the C-terminal end of Octpep-1 displayed enhanced potency and efficacy against melanoma. Octpep-1 reduced the progression of tumours in xenograft melanoma mice and zebrafish. CONCLUSION AND IMPLICATIONS: We unravel the intrinsic anti-tumoural properties of a tachykinin peptide. This peptide mediates the selective cytotoxicity in BRAF-mutated melanoma in vitro and prevents tumour progression in vivo, providing a foundation for a therapy against melanoma.