PT  - JOURNAL ARTICLE
AU  - Nashwa Cheema
AU  - Jessie M. Cameron
AU  - David A. Hood
TI  - Effect of rapamycin on mitochondria and lysosomes in fibroblasts from patients with mtDNA mutations
AID  - 10.1101/2021.03.31.437507
DP  - 2021 Jan 01
TA  - bioRxiv
PG  - 2021.03.31.437507
4099  - http://biorxiv.org/content/early/2021/04/01/2021.03.31.437507.short
4100  - http://biorxiv.org/content/early/2021/04/01/2021.03.31.437507.full
AB  - Maintaining mitochondrial function and dynamics is crucial for cellular health. In muscle, defects in mitochondria result in severe myopathies where accumulation of damaged mitochondria causes deterioration and dysfunction. Importantly, understanding the role of mitochondria in disease is a necessity to determine future therapeutics. One of the most common myopathies is mitochondrial encephalopathy lactic acidosis stroke-like episodes (MELAS), which has no current treatment. Recently, MELAS patients treated with rapamycin exhibited improved clinical outcomes. However, the cellular mechanisms of rapamycin effects in MELAS patients are currently unknown. In this study, we used cultured skin fibroblasts as a window into the mitochondrial dysfunction evident in MELAS cells, as well as to study the mechanisms of rapamycin action, compared to control, healthy individuals. We observed that mitochondria from patients were fragmented, had a 3-fold decline in the average speed of motility, a 2-fold reduced mitochondrial membrane potential and a 1.5–2-fold decline in basal respiration. Despite the reduction in mitochondrial function, mitochondrial import protein Tim23 was elevated in patient cell lines. MELAS fibroblasts had increased MnSOD, p62 and lysosomal function when compared to healthy controls. Treatment of MELAS fibroblasts with rapamycin for 24 hrs resulted in increased mitochondrial respiration compared to control cells, a higher lysosome content, and a greater localization of mitochondria to lysosomes. Our studies suggest that rapamycin has the potential to improve cellular health even in the presence of mtDNA defects, primarily via an increase in lysosomal content.Competing Interest StatementThe authors have declared no competing interest.