bims-resufa 2024-03-31 papers

Issue of 2024‒03‒31
four papers selected by
Gavin McStay, Liverpool John Moores University

IUBMB Life. 2024 Mar 26.

Mitochondrial respiratory supercomplexes of the yeast Saccharomyces cerevisiae.

Mazzen H Eldeeb, Lizeth J Camacho Lopez, Flavia Fontanesi.

The functional and structural relationship among the individual components of the mitochondrial respiratory chain constitutes a central aspect of our understanding of aerobic catabolism. This interplay has been a subject of intense debate for over 50 years. It is well established that individual respiratory enzymes associate into higher-order structures known as respiratory supercomplexes, which represent the evolutionarily conserved organizing principle of the mitochondrial respiratory chain. In the yeast Saccharomyces cerevisiae, supercomplexes are formed by a complex III homodimer flanked by one or two complex IV monomers, and their high-resolution structures have been recently elucidated. Despite the wealth of structural information, several proposed supercomplex functions remain speculative and our understanding of their physiological relevance is still limited. Recent advances in the field were made possible by the construction of yeast strains where the association of complex III and IV into supercomplexes is impeded, leading to diminished respiratory capacity and compromised cellular competitive fitness. Here, we discuss the experimental evidence and hypotheses relative to the functional roles of yeast respiratory supercomplexes. Moreover, we review the current models of yeast complex III and IV assembly in the context of supercomplex formation and highlight the data scattered throughout the literature suggesting the existence of cross talk between their biogenetic processes.

Keywords: III2IV1; III2IV2; OXPHOS biogenesis; Saccharomyces cerevisiae; cellular respiratory capacity; mitochondrial respiratory supercomplexes

DOI: https://doi.org/10.1002/iub.2817

Sci Rep. 2024 Mar 28. 14(1): 7411

High OXPHOS efficiency in RA-FUdr-differentiated SH-SY5Y cells: involvement of cAMP signalling and respiratory supercomplexes.

Maria Laura Matrella, Alessio Valletti, Isabella Gigante, Domenico De Rasmo, Anna Signorile, Silvia Russo, Simona Lobasso, Donatella Lobraico, Michele Dibattista, Consiglia Pacelli, Tiziana Cocco.

Neurons are highly dependent on mitochondria to meet their bioenergetic needs and understanding the metabolic changes during the differentiation process is crucial in the neurodegeneration context. Several in vitro approaches have been developed to study neuronal differentiation and bioenergetic changes. The human SH-SY5Y cell line is a widely used cellular model and several differentiation protocols have been developed to induce a neuron-like phenotype including retinoic acid (RA) treatment. In this work we obtained a homogeneous functional population of neuron-like cells by a two-step differentiation protocol in which SH-SY5Y cells were treated with RA plus the mitotic inhibitor 2-deoxy-5-fluorouridine (FUdr). RA-FUdr treatment induced a neuronal phenotype characterized by increased expression of neuronal markers and electrical properties specific to excitable cells. In addition, the RA-FUdr differentiated cells showed an enrichment of long chain and unsaturated fatty acids (FA) in the acyl chain composition of cardiolipin (CL) and the bioenergetic analysis evidences a high coupled and maximal respiration associated with high mitochondrial ATP levels. Our results suggest that the observed high oxidative phosphorylation (OXPHOS) capacity may be related to the activation of the cyclic adenosine monophosphate (cAMP) pathway and the assembly of respiratory supercomplexes (SCs), highlighting the change in mitochondrial phenotype during neuronal differentiation.

DOI: https://doi.org/10.1038/s41598-024-57613-x

J Xenobiot. 2024 Feb 27. 14(1): 308-319

Xenobiotics Triggering Acute Intermittent Porphyria and Their Effect on Mouse Brain Respiratory Complexes.

Johanna Romina Zuccoli, María Del Carmen Martínez, Pablo Vallecorsa, Ana María Buzaleh.

Heme enzyme dysfunction causes a group of diseases called porphyrias. Particularly, a decrease in porphobilinogen deaminase, involved in the third step of heme biosynthesis, leads to acute intermittent porphyria (AIP). Considering our previous works demonstrating the multiplicity of brain metabolisms affected by porphyrinogenic agents, this study aimed to elucidate whether they cause any alteration on the mitochondrial respiratory chain. The activities of respiratory chain complexes (I to IV) were measured in encephalon mitochondria of CF1 male mice receiving volatile anesthetics: isoflurane (2 mL/kg) and sevoflurane (1.5 mL/kg), ethanol (30%), allylisopropylacetamide (AIA) (350 mg/kg), and barbital (167 mg/kg). Moreover, they were compared versus animals with pathological levels of 5-aminolevulinic acid (ALA, 40 mg/kg). Complex I-III activity was induced by isoflurane and decreased by AIA, ethanol, and ALA. Complex II-III activity was increased by sevoflurane and decreased by isoflurane and AIA. Complex II activity was increased by sevoflurane and barbital and decreased by AIA, ethanol, and ALA. Complex IV activity was increased by barbital and ALA and decreased by sevoflurane. The damage to the respiratory chain by ALA could be reflecting the pathophysiological condition of patients with AIP. Better understanding the broad effect of porphyrinogenic drugs and the mechanisms acting on the onset of AIP is vital in translational medicine.

Keywords: 5-aminolevulinic acid; acute intermittent porphyria; isoflurane; mitochondria; porphyrinogenic agents; respiratory chain complexes; sevoflurane

DOI: https://doi.org/10.3390/jox14010019

J Biol Chem. 2024 Mar 27. pii: S0021-9258(24)01732-0. [Epub ahead of print] 107235

Deafness-associated tRNAPhe mutation impaired mitochondrial and cellular integrity.

Xiaowan Chen, Feilong Meng, Chao Chen, Shujuan Li, Zhiqiang Chou, Baicheng Xu, Jun Q Mo, Yufen Guo, Min-Xin Guan.

Defects in mitochondrial RNA metabolism have been linked to sensorineural deafness that often occurs as a consequence of damaged or deficient inner ear hair cells. In this report, we investigated the molecular mechanism underlying a deafness-associated tRNAPhe 593T>C mutation that changed a highly conserved uracil to cytosine at the position 17 of DHU-loop. The m.593T>C mutation altered tRNAPhe structure and function, including increased melting temperature, resistance to S1 nuclease-mediated digestion and conformational changes. The aberrant tRNA metabolism impaired mitochondrial translation, which was especially pronounced by decreases in levels of ND1, ND5, CYTB, CO1 and CO3 harboring higher numbers of phenylalanine. These alterations resulted in aberrant assembly, instability and reduced activities of respiratory chain enzyme complexes I, III, IV and intact supercomplexes overall. Furthermore, we found that the m.593T>C mutation caused markedly diminished membrane potential, and increased the production of reactive oxygen species in the mutant cell lines carrying the m.593T>C mutation. These mitochondrial dysfunctions led to the mitochondrial dynamic imbalance via increasing fission with abnormal mitochondrial morphology. Excessive fission impaired the process of autophagy including initiation phase, formation and maturation of the autophagosome. In particular, the m.593T>C mutation upregulated the PARKIN-dependent mitophagy pathway. These alterations promoted an intrinsic apoptotic process for the removal of damaged cells. Our findings provide critical insights into the pathophysiology of maternally inherited deafness arising from tRNA mutation-induced defects in mitochondrial and cellular integrity.

Keywords: apoptosis; deafness; mitochondrial dynamics; mitochondrial tRNA mutation; mitophagy

DOI: https://doi.org/10.1016/j.jbc.2024.107235