bims-cytox1 2021-05-09 papers

Issue of 2021–05–09
three papers selected by
Gavin McStay, Staffordshire University

Nat Protoc. 2021 May 05.

Monitoring mammalian mitochondrial translation with MitoRiboSeq.

Sophia Hsin-Jung Li, Michel Nofal, Lance R Parsons, Joshua D Rabinowitz, Zemer Gitai.

Several essential components of the electron transport chain, the major producer of ATP in mammalian cells, are encoded in the mitochondrial genome. These 13 proteins are translated within mitochondria by 'mitoribosomes'. Defective mitochondrial translation underlies multiple inborn errors of metabolism and has been implicated in pathologies such as aging, metabolic syndrome and cancer. Here, we provide a detailed ribosome profiling protocol optimized to interrogate mitochondrial translation in mammalian cells (MitoRiboSeq), wherein mitoribosome footprints are generated with micrococcal nuclease and mitoribosomes are separated from cytosolic ribosomes and other RNAs by ultracentrifugation in a single straightforward step. We highlight critical steps during library preparation and provide a step-by-step guide to data analysis accompanied by open-source bioinformatic code. Our method outputs mitoribosome footprints at single-codon resolution. Codons with high footprint densities are sites of mitoribosome stalling. We recently applied this approach to demonstrate that defects in mitochondrial serine catabolism or in mitochondrial tRNA methylation cause stalling of mitoribosomes at specific codons. Our method can be applied to study basic mitochondrial biology or to characterize abnormalities in mitochondrial translation in patients with mitochondrial disorders.

DOI: https://doi.org/10.1038/s41596-021-00517-1

Int J Mol Sci. 2021 Apr 30. pii: 4793. [Epub ahead of print]22(9):

Mitochondrial Transplantation as a Novel Therapeutic Strategy for Mitochondrial Diseases.

Anna Park, Mihee Oh, Su Jeong Lee, Kyoung-Jin Oh, Eun-Woo Lee, Sang Chul Lee, Kwang-Hee Bae, Baek Soo Han, Won Kon Kim.

Mitochondria are the major source of intercellular bioenergy in the form of ATP. They are necessary for cell survival and play many essential roles such as maintaining calcium homeostasis, body temperature, regulation of metabolism and apoptosis. Mitochondrial dysfunction has been observed in variety of diseases such as cardiovascular disease, aging, type 2 diabetes, cancer and degenerative brain disease. In other words, the interpretation and regulation of mitochondrial signals has the potential to be applied as a treatment for various diseases caused by mitochondrial disorders. In recent years, mitochondrial transplantation has increasingly been a topic of interest as an innovative strategy for the treatment of mitochondrial diseases by augmentation and replacement of mitochondria. In this review, we focus on diseases that are associated with mitochondrial dysfunction and highlight studies related to the rescue of tissue-specific mitochondrial disorders. We firmly believe that mitochondrial transplantation is an optimistic therapeutic approach in finding a potentially valuable treatment for a variety of mitochondrial diseases.

Keywords: mitochondria; mitochondrial disease; mitochondrial dysfunction; mitochondrial function; mitochondrial transplantation

DOI: https://doi.org/10.3390/ijms22094793

FASEB J. 2021 Jun;35(6): e21538

Atp23p and Atp10p coordinate to regulate the assembly of yeast mitochondrial ATP synthase.

Guangying Yang, Yuanyuan Ding, Xiaohui Shang, Tong Zhao, Shan Lu, Jinghan Tian, Jun Weng, Xiaomei Zeng.

Two chaperones, Atp23p and Atp10p, were previously shown to regulate the assembly of yeast mitochondrial ATP synthase, and extra expression of ATP23 was found to partially rescue an atp10 deletion mutant, by an unknown mechanism. Here, we identified that the residues 112-115 (LRDK) of Atp23p were required for its function in assisting assembly of the synthase, and demonstrated both functions of Atp23p, processing subunit 6 precursor and assisting assembly of the synthase, were required for the partial rescue of atp10 deletion mutant. By chasing labeling with isotope 35 S-methionine, we found the stability of subunit 6 of the synthase increased in atp10 null strain upon overexpression of ATP23. Further co-immunoprecipitation (Co-IP) and blue native PAGE experiments showed that Atp23p and Atp10p were physically associated with each other in wild type. Moreover, we revealed the expression level of Atp23p increased in atp10 null mutant compared with the wild type. Furthermore, we found that, after 72 hours growth, atp10 null mutant showed leaky growth on respiratory substrates, presence of low level of subunit 6 and partial recovery of oligomycin sensitivity of mitochondrial ATPase activity. Further characterization revealed the expression of Atp23p increased after 24 hours growth in the mutant. These results indicated, in atp10 null mutant, ATP10 deficiency could be partially complemented with increased expression of Atp23p by stabilizing some subunit 6 of the synthase. Taken together, this study revealed the two chaperones Atp23p and Atp10p coordinated to regulate the assembly of mitochondrial ATP synthase, which advanced our understanding of mechanism of assembly of yeast mitochondrial ATP synthase.

Keywords: Atp10p; Atp23p; assembly; coordinate; mitochondrial ATP synthase

DOI: https://doi.org/10.1096/fj.202002475R