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The opening of the mitochondrial permeability transition pore (PTP), a Ca2+‐dependent pore located in the inner mitochondrial membrane, triggers mitochondrial outer membrane permeabilization (MOMP) and induces organelle rupture. However, the underlying mechanism of PTP‐induced MOMP remains unclear. Mitochondrial carrier homolog 2 (MTCH2) mediates MOMP process by facilitating the recruitment of tBID to mitochondria. Here, we show that MTCH2 binds to cyclophilin D (CyPD) and promotes the dimerization of F‐ATP synthase via interaction with subunit j. The interplay between MTCH2 and subunit j coordinates MOMP and PTP to mediate the occurrence of mitochondrial permeability transition. Knockdown of CyPD, MTCH2 and subunit j markedly sensitizes cells to RSL3‐induced ferroptosis, which is prevented by MitoTEMPO, suggesting that mitochondrial permeability transition mediates ferroptosis defense. [ABSTRACT FROM AUTHOR]

Establishing an ultra-high-precision link for time–frequency comparisons between satellites and ground stations is critically important. This endeavor is fundamental to the advancement of pioneering space science exploration and the development of a robust space-based time–frequency system featuring ultra-high-precision space atomic clocks. In response to the requirements for assessing the long-term stability of high-precision space atomic clocks, we have designed and implemented a satellite–ground microwave time–frequency comparison system and method based on a three-frequency mode. Ground-based experimental results demonstrate that the equipment layer can achieve a satellite–ground time comparison accuracy better than 0.4 ps (RMS), with the equipment delay stability (ADEV) for all three frequencies being better than 8 × 10−18 at 86,400. By leveraging the ground-based experimental results, we constructed a satellite–ground time–frequency comparison simulation and verification platform. This platform realizes ultra-high-precision satellite–ground time–frequency comparison based on the China Space Station (CSS). After correcting various transmission delay errors, the satellite–ground time comparison achieved an accuracy better than 0.8 ps and an ADEV better than 2 × 10−17 at 86,400. This validation of our novel satellite–ground time–frequency comparison system and method, capable of achieving an 10−17 magnitude stability, is not only a significant contribution to the field of space time–frequency systems but also paves the way for future advancements and applications in space science exploration. [ABSTRACT FROM AUTHOR]

Specific emitter identification (SEI) is a professional technology to recognize different emitters by measuring the unique features of received signals. It has been widely used in both civilian and military fields. Recently, many SEI methods based on deep learning have been proposed, most of which assume that the training set and testing set have the same data distribution. However, in reality, the testing set is generally used later than the training set and lacks labels. The long time span may change the signal transmission environment and fingerprint features. These changes result in considerable differences in data distribution between the training and testing sets, thereby affecting the recognition and prediction abilities of the model. Therefore, the existing works cannot achieve satisfactory results for a long time span SEI. To address this challenge and obtain stable fingerprints, we transform the long time span SEI problem into a domain adaptive problem and propose an unsupervised domain adaptive method called LTS-SEI. Noteworthily, LTS-SEI uses a multilayer convolutional feature extractor to learn feature knowledge and confronts a domain discriminator to generate domain-invariant shallow fingerprints. The classifier of LTS-SEI applies feature matching to source domain samples and target domain samples to achieve the domain alignment of deep fingerprints. The classifier further reduces the intraclass diversity of deep features to alleviate the misclassification problem of edge samples in the target domain. To confirm the effectiveness and reliability of LTS-SEI, we collect multiple sets of real satellite navigation signals using two antennas with 13 m- and 40 m-large apertures, respectively, and construct two available datasets. Numerous experiments demonstrate that LTS–SEI can considerably increase the recognition accuracy of the long time span SEI and is superior to the other existing methods. [ABSTRACT FROM AUTHOR]

As a basic task and key link of space situational awareness, space target recognition has become crucial in threat analysis, communication reconnaissance and electronic countermeasures. Using the fingerprint features carried by the electromagnetic signal to recognize is an effective method. Because traditional radiation source recognition technologies are difficult to obtain satisfactory expert features, automatic feature extraction methods based on deep learning have become popular. Although many deep learning schemes have been proposed, most of them are only used to solve the inter-class separable problem and ignore the intra-class compactness. In addition, the openness of the real space may invalidate the existing closed-set recognition methods. In order to solve the above problems, inspired by the application of prototype learning in image recognition, we propose a novel method for recognizing space radiation sources based on a multi-scale residual prototype learning network (MSRPLNet). The method can be used for both the closed- and open-set recognition of space radiation sources. Furthermore, we also design a joint decision algorithm for an open-set recognition task to identify unknown radiation sources. To verify the effectiveness and reliability of the proposed method, we built a set of satellite signal observation and receiving systems in a real external environment and collected eight Iridium signals. The experimental results show that the accuracy of our proposed method can reach 98.34% and 91.04% for the closed- and open-set recognition of eight Iridium targets, respectively. Compared to similar research works, our method has obvious advantages. [ABSTRACT FROM AUTHOR]

The mitochondrial F-ATP synthase is a complex molecular motor arranged in V-shaped dimers that is responsible for most cellular ATP synthesis in aerobic conditions. In the yeast F-ATP synthase, subunits e and g of the FO sector constitute a lateral domain, which is required for dimer stability and cristae formation. Here, by using site-directed mutagenesis, we identified Arg-8 of subunit e as a critical residue in mediating interactions between subunits e and g, most likely through an interaction with Glu-83 of subunit g. Consistent with this hypothesis, (i) the substitution of Arg-8 in subunit e (eArg-8) with Ala or Glu or of Glu-83 in subunit g (gGlu-83) with Ala or Lys destabilized the digitonin-extracted F-ATP synthase, resulting in decreased dimer formation as revealed by blue-native electrophoresis; and (ii) simultaneous substitution of eArg-8 with Glu and of gGlu-83 with Lys rescued digitonin-stable F-ATP synthase dimers. When tested in lipid bilayers for generation of Ca2+-dependent channels, WT dimers displayed the high-conductance channel activity expected for the mitochondrial megachannel/permeability transition pore, whereas dimers obtained at low digitonin concentrations from the Arg-8 variants displayed currents of strikingly small conductance. Remarkably, double replacement of eArg-8 with Glu and of gGlu-83 with Lys restored high-conductance channels indistinguishable from those seen in WT enzymes. These findings suggest that the interaction of subunit e with subunit g is important for generation of the full-conductance megachannel from F-ATP synthase. [ABSTRACT FROM AUTHOR]

Recent years have seen renewed interest in the permeability transition pore, a high conductance channel responsible for permeabilization of the inner mitochondrial membrane, a process that leads to depolarization and Ca 2+ release. Transient openings may be involved in physiological Ca 2+ homeostasis while long-lasting openings may trigger and/or execute cell death. In this review we specifically focus (i) on the hypothesis that the PTP forms from the F-ATP synthase and (ii) on the mechanisms through which Ca 2+ can reversibly switch this energy-conserving nanomachine into an energy-dissipating device. [ABSTRACT FROM AUTHOR]

[Display omitted] Mitochondria are a major source of ATP provision as well as cellular suicidal weapon store. Accumulating evidences demonstrate that mitochondrial bioenergetics, biosynthesis and signaling are important mediators of tumorigenesis. Metabolic plasticity enables cancer cell reprogramming to cope with cellular and environmental alterations, a process requires mitochondria biology. Mitochondrial metabolism emerges to be a promising arena for cancer therapeutic targets. The permeability transition pore (PTP) participates in physiological Ca2+ and ROS homeostasis as well as cell death depending on the open state. The hypothesis that PTP forms from F-ATP synthase provides clues to the potential collaborative role of mitochondrial respiration and PTP in regulating cancer cell fate and metabolic reprogramming. [ABSTRACT FROM AUTHOR]