Volume 49 Number 3

Mitochondrial respiration leak spurs chemoresistance in MT-ND5 mutant cybrids by suppressing mitophagy

Mohd Fazirul Mustafa^a, Sharida Fakurazi^a, Maizaton Atmadini Abdullah^b, Sandra Maniam^a,*

 
ABSTRACT:     Mitochondrial genomes have high mutation rate due to oxidative damage caused by reactive oxygen species (ROS). The gene encoding subunit 5 of complex I (ND5) was previously reported as a hotspot for mitochondrial DNA mutations in cancer tissues. This prompted us to investigate the role of ND5 mutation in cell proliferation, mitochondria bioenergetics, and cellular quality control that includes autophagy and mitophagy. Cybrid cell lines were developed using 3 commercial cell lines, CRL-1739, HGT-1 and MDA-MB-231 which harbour ND5 mutations. Cell proliferation was assessed through cell viability assays, and data on mitochondrial bioenergetics were obtained by measuring the oxygen consumption rate. Protein markers related to autophagy and mitophagy were evaluated using both immunoblotting and immunofluorescence. The cybrid lines showed significantly higher cell proliferation rate with significantly lower cell death compared to the negative control cells. The mitochondria bioenergetic assay reported an increase in basal respiration and proton leak but a decrease in spare respiratory capacity in cybrid cells compared to the negative control cells. The autophagy and mitophagy protein markers, were significantly decreased compared to negative control except the expression of BNIP-3. This study demonstrated that ND5 mutations resulted in increased proton leak which indicates increased ROS generation and mitochondrial dysfunction. The increased non-mitochondrial respiration is associated with altered metabolic intermediates that further promotes cancer cell viability and proliferation rate. The disruption of mitochondrial bioenergetics, which leads to accumulation of damaged mitochondria, may contribute to compromised cellular quality control, ultimately leading to tumorigenesis.

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* Corresponding author, E-mail: sandra@upm.edu.my

Received 7 Jun 2024, Accepted 0 0000