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Mitochondria are essential for cellular metabolism, serving as the primary source of adenosine triphosphate (ATP). This energy is generated by the oxidative phosphorylation (OXPHOS) system located in the inner mitochondrial membrane. Impairments in this machinery are linked to serious human diseases, especially in tissues with high energy demands. Assembly of the OXPHOS system requires the coordinated expression of genes encoded by both the nuclear and mitochondrial genomes. The mitochondrial DNA encodes for 13 protein components, which are synthesized by mitochondrial ribosomes and inserted into the inner membrane during translation. Despite progress, key aspects of how mitochondrial gene expression is regulated remain elusive, largely due to the organelle’s limited genetic accessibility. However, emerging technologies now offer new tools to manipulate various stages of this process. In this review, we explore recent strategies that expand our ability to target mitochondria genetically.

Mitochondrial function relies heavily on the proper targeting and insertion of nuclear-encoded proteins into the outer mitochondrial membrane (OMM), a process mediated by specialised biogenesis factors known as insertases. These insertases are essential for the membrane integration of α-helical OMM proteins, which contain one or multiple hydrophobic transmembrane segments. While the general mechanisms of mitochondrial protein import are well established, recent research has shed light on the diversity and evolutionary conservation of OMM insertases across eukaryotic lineages. In Saccharomyces cerevisiae , the mitochondrial import (MIM) complex, composed of Mim1 and Mim2, facilitates the integration of various α-helical OMM proteins, often in cooperation with import receptors such as Tom20 and Tom70. In Trypanosoma brucei , the functional MIM counterpart pATOM36 performs a similar role despite lacking sequence and structural homology, reflecting a case of convergent evolution. In mammals, MTCH2 has emerged as the principal OMM insertase, with MTCH1 playing a secondary, partially redundant role. This review provides a comparative analysis of these insertases, emphasising their conserved functionality, species-specific adaptations, and mechanistic nuances.

The mitochondrial solute carrier family, also called SLC25 family, comprises a group of structurally and evolutionary related transporters that are embedded in the mitochondrial inner membrane. About 35 and 53 mitochondrial carrier proteins are known in yeast and human cells, respectively, which transport nucleotides, metabolites, amino acids, fatty acids, inorganic ions and cofactors across the inner membrane. They are proposed to function by a common rocker-switch mechanism, alternating between conformations that expose substrate-binding pockets to the intermembrane space (cytoplasmic state) and to the matrix (matrix state). The substrate specificities of both states differ so that carriers can operate as antiporters, symporters or uniporters. Carrier proteins share a characteristic structure comprising six transmembrane domains and expose both termini to the intermembrane space. Most carriers lack N-terminal presequences but use carrier-specific internal targeting signals that direct them into mitochondria via a specific import route, known as the ‘carrier pathway’. Owing to their hydrophobicity and aggregation-prone nature, the mistargeting of carriers can lead to severe proteotoxic stress and diseases. In this review article, we provide an overview about the structure, biogenesis and physiology of carrier proteins, focusing on baker’s yeast where their biology is particularly well characterized.

The application of synthetic riboswitches or aptamer-based biosensors for the monitoring of engineered metabolic pathways greatly depends on a high degree of target molecule specificity. Since metabolic pathways include close derivatives that often differ only in single moieties, the binding specificity of aptamers utilized for these systems has to be high. In the present study, we selected an RNA aptamer that is highly specific in its binding to homoeriodictyol while discriminating its close derivatives eriodictyol and naringenin. This high degree in specificity was achieved through three consecutive SELEX approaches while the selection parameters were adjusted and refined from one to the next. The adjustments along the process, with the selection outcome and next-generation sequencing analysis of the selection rounds, led to valuable insights into the stringency necessary to facilitate target specificity in aptamers obtained from SELEX. From the third selection, we obtained a highly binding specific aptamer and examined its structure and binding properties. Overall, our results connect the importance of selection stringency with SELEX outcome and aptamer specificity while providing a highly selective, homoeriodictyol-binding RNA aptamer.

Tripterygium wilfordii has been used for a long time to treat autoimmune diseases. Its toxic side effects limit its clinical application. Mitophagy plays a protective role in various diseases. TANK-binding kinase 1 (TBK1) is a mitophagy-promoting molecule. This study aimed to investigate whether TBK1 could alleviate triptolide (TP)-induced nephrotoxicity by regulating mitophagy. To establish TP-induced nephrotoxic injury in animal model, 16 Sprague-Dawley rats were administered with TP by gavage, then renal tissues were collected for hematoxylin and eosin (HE) staining, western blotting and immunofluorescence analysis. To investigate whether up-regulation of TBK1 could alleviate TP-induced nephrotoxic injury and the specific mechanism, HK-2 cells were cultured in vitro , transfected with TBK1-overexpression recombinant lentivirus, then treated with TP. Western blotting, immunofluorescence, flow cytometry, multifunctional microplate detector were used to detect the relevant molecules. Here we found that TP caused kidney function damage, declined mitophagy levels, decreased the expression of TBK1 and mitophagy-related proteins in rats. TP stimulation decreased cell viability, mitochondrial membrane potential, mitophagy-protein, the formation of mito-autophagosomes and mito-autophagolysosomes in HK-2 cells. Upregulating TBK1 could reverse these damages. In summary, TP-induced cell injury had decreased mitophagy levels. Up-regulating TBK1 could increase mitophagy and further alleviate TP-induced cell injury.

Gastric cancer is the most common digestive malignant tumor worldwild. EDD1 was reported to be frequently amplified in several tumors and played an important role in the tumorigenesis process. However, the biological role and potential mechanism of EDD1 in gastric cancer remains poorly understood. In this study, we are aim to investigate the effect of EDD1 on gastric cancer progression and to explore the underlying mechanism. The results showed the significant up-regulation of EDD1 in -gastric cancer cell tissues and lines. The expression level of EDD1 was also positively associated with advanced clinical stages and predicted poor overall patient survival and poor disease-free patient survival. Besides, EDD1 knockdown markedly inhibited cell viability, colony formation, and suppressed tumor growth. Opposite results were obtained in gastric cancer cells with EDD1 overexpression. EDD1 knockdown was also found to induce gastric cancer cells apoptosis. Further investigation indicated that the oncogenic role of EDD1 in regulating gastric cancer cells growth and apoptosis was related to its PABC domain and directly through targeting miR-22, which was significantly down-regulated in gastric cancer tissues. Totally, our study suggests that EDD1 plays an oncogenic role in gastric cancer and may be a potential therapeutic target for gastric cancer.

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Recent studies have demonstrated that acquisition of epithelial-mesenchymal transition (EMT) is associated with drug resistance in lung cancer cells. However, the underlying mechanisms are not fully elucidated. Emerging evidence suggests that microRNAs play a crucial role in controlling EMT. The aim of this study was to explore the potential role of miR-125b in governing EMT in paclitaxel-resistant (PR) lung cancer cells. To achieve this goal, we explored the role of miR-125b in regulation of EMT in stable PR lung cancer cells, namely A549-PR and H460-PR. We found that miR-125b was significantly downregulated in A549-PR and H460-PR cells. Notably, ectopic expression of miR-125b led to the reversal of EMT phenotype. Moreover, we found that miR-125b governed PR-induced EMT partly due to down-regulation of its target Sema4C. More importantly, overexpression of miR-125b or depletion of Sema4C sensitized PR cells to paclitaxel. Furthermore, stable overexpression miR-125b in A549-PR cells inhibited tumor xenograft growth in immunodeficient mice. Our study implied that up-regulation of miR-125b could be a novel approach to reverse chemotherapy resistance in lung cancers.