bims-cytox1 2021-09-05 papers

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

Mitochondrion. 2021 Aug 25. pii: S1567-7249(21)00114-8. [Epub ahead of print]

Leber's Hereditary Optic Neuropathy: Current approaches and future perspectives on Mesenchymal stem cell-mediated rescue.

Mohana Devi Subramaniam, B Abishek Kumar, Mahalaxmi Iyer, Balachandar Vellingiri.

Leber's Hereditary Optic Neuropathy (LHON) is an inherited optic nerve disorder. It is a mitochondrially inherited disease due to point mutation in the MT-ND1, MT-ND4, and MT-ND6 genes of mitochondrial DNA (mtDNA) coding for complex I subunit proteins. These mutations affect the assembly of the mitochondrial complex I and hence the electron transport chain leading to mitochondrial dysfunction and oxidative damage. Optic nerve cells like retinal ganglion cells (RGCs) are more sensitive to mitochondrial loss and oxidative damage which results in the progressive degeneration of RGCs at the axonal region of the optic nerve leading to bilateral vision loss. Currently, gene therapy using Adeno-associated viral vector (AAV) is widely studied for the therapeutics application in LHON. Our review highlights the application of cell-based therapy for LHON. Mesenchymal stem cells (MSCs) are known to rescue cells from the pre-apoptotic stage by transferring healthy mitochondria through tunneling nanotubes (TNT) for cellular oxidative function. Empowering the transfer of healthy mitochondria using MSCs may replace the mitochondria with pathogenic mutation and possibly benefit the cells from progressive damage. This review discusses the ongoing research in LHON and mitochondrial transfer mechanisms to explore its scope in inherited optic neuropathy.

Keywords: Cell-mediated rescue; LHON; Mesenchymal stem cell; Mitochondrial dysfunction; Mitochondrial transfer; Tunneling nanotubes

DOI: https://doi.org/10.1016/j.mito.2021.08.013

Front Physiol. 2021 ;12 693734

Leigh Syndrome: A Tale of Two Genomes.

Ajibola B Bakare, Edward J Lesnefsky, Shilpa Iyer.

Leigh syndrome is a rare, complex, and incurable early onset (typically infant or early childhood) mitochondrial disorder with both phenotypic and genetic heterogeneity. The heterogeneous nature of this disorder, based in part on the complexity of mitochondrial genetics, and the significant interactions between the nuclear and mitochondrial genomes has made it particularly challenging to research and develop therapies. This review article discusses some of the advances that have been made in the field to date. While the prognosis is poor with no current substantial treatment options, multiple studies are underway to understand the etiology, pathogenesis, and pathophysiology of Leigh syndrome. With advances in available research tools leading to a better understanding of the mitochondria in health and disease, there is hope for novel treatment options in the future.

Keywords: Leigh syndrome; mitochondria; mitochondrial DNA; mitochondrial genetics; respiratory chain complex

DOI: https://doi.org/10.3389/fphys.2021.693734

Bio Protoc. 2021 Aug 05. 11(15): e4110

Purification of Mitochondrial Ribosomes with the Translocase Oxa1L from HEK Cells.

Hanting Yang, Nirupa Desai.

Mitochondrial ribosomes (mitoribosomes) perform protein synthesis inside mitochondria, the organelles responsible for energy conversion and adenosine triphosphate (ATP) production in eukaryotic cells. To investigate their functions and structures, large-scale purification of intact mitoribosomes from mitochondria-rich animal tissues or HEK cells have been developed. However, the fast purification of mitoribosomes anchored to the mitochondrial inner membrane in complex with the Oxa1L translocase remains particularly challenging. Herein, we present a protocol recently developed and modified in our lab that provides details for the efficient isolation of intact mitoribosomes with its translocase Oxa1L. We combined the cell culture of PDE12-/- or wild-type HEK293 cell lines with the isolation of mitochondria and the purification steps used for the biochemical and structural studies of mitoribosomes and Oxa1L. Graphic abstract: Schematic procedure for the purification of mitoribosomes from HEK cells. The protocol described herein includes two main sections: 1) isolation of mitochondria from HEK cells; and 2) purification of mitoribosome-Oxa1L from mitochondria. RB: Resuspension Buffer (see Recipes) (Created with BioRender.com).

Keywords: Biochemistry; Cryo-EM; Mitochondria; Mitoribosome; Oxa1L; Ribosome purification

DOI: https://doi.org/10.21769/BioProtoc.4110

J Biol Chem. 2021 Aug 27. pii: S0021-9258(21)00936-4. [Epub ahead of print] 101135

Aim32 is a dual-localized 2Fe-2S mitochondrial protein that functions in redox quality control.

Danyun Zhang, Owen R Dailey, Daniel J Simon, Kamilah Roca-Datzer, Yasaman Jami-Alahmadi, Mikayla S Hennen, James A Wolfschlegel, Carla M Koehler, Deepa V Dabir.

Yeast is a facultative anaerobe and uses diverse electron acceptors to maintain redox-regulated import of cysteine-rich precursors via the mitochondrial intermembrane space assembly (MIA) pathway. With the growing diversity of substrates utilizing the MIA pathway, understanding the capacity of the intermembrane space (IMS) to handle different types of stress is crucial. We used mass spectrometry to identify additional proteins that interacted with the sulfhydryl oxidase Erv1 of the MIA pathway. Aim32, a thioredoxin-like [2Fe-2S] ferredoxin protein, was identified as an Erv1 binding protein. Detailed localization studies showed that Aim32 resided in both the mitochondrial matrix and IMS. Aim32 interacted with additional proteins including redox protein Osm1 and protein import components Tim17, Tim23, and Tim22. Deletion of Aim32 or mutation of conserved cysteine residues that coordinate the Fe-S center in Aim32 resulted in an increased accumulation of proteins with aberrant disulfide linkages. In addition, the steady-state level of assembled TIM22, TIM23, and Oxa1 protein import complexes was decreased. Aim32 also bound to several mitochondrial proteins under nonreducing conditions, suggesting a function in maintaining the redox status of proteins by potentially targeting cysteine residues that may be sensitive to oxidation. Finally, Aim32 was essential for growth in conditions of stress such as elevated temperature and hydroxyurea (HU), and under anaerobic conditions. These studies suggest that the Fe-S protein Aim32 has a potential role in general redox homeostasis in the matrix and IMS. Thus, Aim32 may be poised as a sensor or regulator in quality control for a broad range of mitochondrial proteins.

Keywords: disulfide; mitochondria; mitochondrial transport; protein import; redox regulation; thiol; thioredoxin

DOI: https://doi.org/10.1016/j.jbc.2021.101135

Biomaterials. 2021 Aug 28. pii: S0142-9612(21)00464-6. [Epub ahead of print]277 121108

Gene therapy strategies for rare monogenic disorders with nuclear or mitochondrial gene mutations.

Yi Wang, Li-Fan Hu, Tian-Jiao Zhou, Lian-Yu Qi, Lei Xing, Jaiwoo Lee, Feng-Zhen Wang, Yu-Kyoung Oh, Hu-Lin Jiang.

Rare monogenic disorders are a group of single-gene-mutated diseases that have a low incidence rate (less than 0.5‰) and eventually lead to patient disability and even death. Due to the relatively low number of people affected, these diseases typically fail to attract a great deal of commercial investment and research interest, and the affected patients thus have unmet medical needs. Advances in genomics biology, gene editing, and gene delivery can now offer potentially effective options for treating rare monogenic diseases. Herein, we review the application of gene therapy strategies (traditional gene therapy and gene editing) against various rare monogenic diseases with nuclear or mitochondrial gene mutations, including eye, central nervous system, pulmonary, systemic, and blood cell diseases. We summarize their pathologic features, address the barriers to gene delivery for these diseases, discuss available therapies in the clinic and in clinical trials, and sum up in-development gene delivery systems for various rare monogenic disorders. Finally, we elaborate the possible directions and outlook of gene therapy for rare monogenic disorders.

Keywords: Gene delivery systems; Gene editing; Gene therapy; Rare monogenic disorders

DOI: https://doi.org/10.1016/j.biomaterials.2021.121108