Cryo-EM structure of the mammalian ATP synthase tetramer bound with inhibitory protein IF1.
Science (New York, N.Y.)
The mitochondrial adenosine triphosphate (ATP) synthase produces most of the ATP required by mammalian cells. We isolated porcine tetrameric ATP synthase and solved its structure at 6.2-angstrom resolution using a single-particle cryo-electron microscopy method. Two classical V-shaped ATP synthase dimers lie antiparallel to each other to form an H-shaped ATP synthase tetramer, as viewed from the matrix. ATP synthase inhibitory factor subunit 1 (IF1) is a well-known in vivo inhibitor of mammalian ATP synthase at low pH. Two IF1 dimers link two ATP synthase dimers, which is consistent with the ATP synthase tetramer adopting an inhibited state. Within the tetramer, we refined structures of intact ATP synthase in two different rotational conformations at 3.34- and 3.45-Å resolution.
10.1126/science.aaw4852
Nrg1/ErbB signaling networks in Schwann cell development and myelination.
Newbern Jason,Birchmeier Carmen
Seminars in cell & developmental biology
Neuregulin-1 (Nrg1) provides a key axonal signal that regulates Schwann cell proliferation, migration and myelination through binding to ErbB2/3 receptors. The analysis of a number of genetic models has unmasked fundamental mechanisms underlying the specificity of the Nrg1/ErbB signaling axis. Differential expression of Nrg1 isoforms, Nrg1 processing, and ErbB receptor localization and trafficking represent important regulatory themes in the control of Nrg1/ErbB function. Nrg1 binding to ErbB2/3 receptors results in the activation of intracellular signal transduction pathways that initiate changes in Schwann cell behavior. Here, we review data that has defined the role of key Nrg1/ErbB signaling components like Shp2, ERK1/2, FAK, Rac1/Cdc42 and calcineurin in development of the Schwann cell lineage in vivo. Many of these regulators receive converging signals from other cues that are provided by Notch, integrin or G-protein coupled receptors. Signaling by multiple extracellular factors may act as key modifiers and allow Schwann cells at different developmental stages to respond in distinct manners to the Nrg1/ErbB signal.
10.1016/j.semcdb.2010.08.008
Resveratrol regulates the recovery of rat sciatic nerve crush injury by promoting the autophagy of Schwann cells.
Zhang Jiayi,Ren Jingyan,Liu Yang,Huang Dongxu,Lu Laijin
Life sciences
Resveratrol has the ability to promote functional recovery after sciatic nerve crush injury (SNCI), though the mechanism through which this occurs in not fully understood. Resveratrol can promote autophagy, a key process in Wallerian degeneration; thus, we hypothesized that resveratrol could promote recovery from SNCI by promoting Schwann cell autophagy and acceleration of Wallerian degeneration. Motor function recovery was assessed by calculating Sciatic Function Indexes (SFIs) at days 7, 14, 21, 28 post SNCI. Autophagy and myelin clearance were assessed by microtubule-associated protein light chain 3B (LC3B) and myelin protein zero (MPZ) immunofluorescence and Western blot analysis on the fourth day after SNCI. The autophagy of Schwann cells following resveratrol administration was quantified by immunofluorescence in RSC96 cells. Immunofluorescence and Transmission electron microscopy (TEM) were also used in Resveratrol treated sciatic nerve four days post-SNCI to find LC3B positive areas and typical double membrane structures represent for autophagy. The SNCI+resveratrol (crush+Res) groups recovered faster than the SNCI+vehicles (crush+V) group. On day four, almost all of the myelin had regenerated in the crush+Res rats, while the crush+V group's myelin remained intact and the expression levels of LC3-II/I was the highest. On day 28 post-injury, both the control and crush+Res groups' myelin neurofibers reached peak numbers as did the thickness of the myelin sheath. Both in vitro and in vivo immunofluorescence showed that LC3B was colocalized with Schwann cells. This is the first study to observe that resveratrol can promote recovery from SCNI by accelerating the myelin clearance process by promoting autophagy of Schwann cells.
10.1016/j.lfs.2020.117959
Genome-wide RNAi screen identifies ATPase inhibitory factor 1 (ATPIF1) as essential for PARK2 recruitment and mitophagy.
Autophagy
Mitochondrial dysfunction is a hallmark of aging and numerous human diseases, including Parkinson disease (PD). Multiple homeostatic mechanisms exist to ensure mitochondrial integrity, including the selective autophagic program mitophagy, that is activated during starvation or in response to mitochondrial dysfunction. Following prolonged loss of potential across the inner mitochondrial membrane (ΔΨ), PTEN-induced putative kinase 1 (PINK1) and the E3-ubiquitin ligase PARK2 work in the same pathway to trigger mitophagy of dysfunctional mitochondria. Mutations in PINK1 and PARK2, as well as PARK7/DJ-1, underlie autosomal recessive Parkinsonism and impair mitochondrial function and morphology. In a genome-wide RNAi screen searching for genes that are required for PARK2 translocation to the mitochondria, we identified ATPase inhibitory factor 1 (ATPIF1/IF1) as essential for PARK2 recruitment and mitophagy in cultured cells. During uncoupling, ATPIF1 promotes collapse of ΔΨ and activation of the PINK-PARK2 mitophagy pathway by blocking the ATPase activity of the F 1-Fo ATP synthase. Restoration of ATPIF1 in Rho0 cells, which lack mtDNA and a functional electron transport chain, lowers ΔΨ and triggers PARK2 recruitment. Our findings identified ATPIF1 and the ATP synthase as novel components of the PINK1-PARK2 mitophagy pathway and provide genetic evidence that loss of ΔΨ is an essential trigger for mitophagy.
10.4161/auto.25413
Peripheral nerve repair with epimysium conduit.
Yang Xiao-Nan,Jin Yu-Qing,Bi Hui,Wei Wu,Cheng Jia,Liu Zhang-Yin,Shen Zunli,Qi Zuo-Liang,Cao Yilin
Biomaterials
Autologous tissues such as skeletal muscle have high biocampatibility and can effectively promote nerve regeneration compared to other biological and artificial materials; however, the reasonable and effective application of skeletal muscle requires further study. The purpose of this investigation was to assess the possibility of preparing a hollow nerve conduit, termed the epimysium conduit (EMC), using thin crimps of epimysium with skeletal muscle fibers and evaluate its effectiveness in repairing peripheral nerve defects. We prepared nerve conduits containing lumen with the external oblique muscle of the CAG-EFGP transgenic mice using microsurgical techniques for bridge repair of a 5-mm long sciatic nerve defect in wild-type mice. Systematic histological and functional assessments of the regenerated nerves were performed 8 and 12 weeks after surgery. EMC was found to effectively repair the sciatic nerve defect with significantly greater effectiveness than artificial conduits; however, the repair effect of EMC was lower than that of autologous nerve grafting for some parameters. In addition, our findings showed that some EMC-derived cell components migrated into the region of the regenerated nerves and contributed to reconstruction. Based on these findings, we conclude that a hollow conduit prepared with epimysium and a few skeletal muscle fibers is ideal for repairing peripheral nerve defects, and the cell components in the grafts contribute to nerve regeneration and structural remodeling, which provides an alternative option for the emergency primary repair of peripheral nerve defects in clinical practice.
10.1016/j.biomaterials.2013.04.018
Nanosilver incurs an adaptive shunt of energy metabolism mode to glycolysis in tumor and nontumor cells.
Chen Yue,Wang Zhe,Xu Ming,Wang Xiang,Liu Rui,Liu Qian,Zhang Zhihong,Xia Tian,Zhao Jincai,Jiang Guibin,Xu Yong,Liu Sijin
ACS nano
Due to its significant antimicrobial properties, nanosilver (nAg) has been substantially used in a wide spectrum of areas. This has raised the concerns on the detrimental effects on environment and human health. Although numerous studies have documented nAg-mediated toxicity to cells or organisms, little attempt has been made to study the biological impacts of nAg on cells at nontoxic concentrations, namely, the distinct biological effects that can be separated from direct cytotoxicity. Here, we studied nAg-mediated effects on energy metabolism in cells under sublethal exposure. Treatment of nAg at nontoxic concentrations resulted in a decline of ATP synthesis and attenuation of respiratory chain function in nontumor HEK293T cells and tumor cells with differential respiration rate, including HepG2, HeLa, A498, and PC3 cells. Cellular energy homeostasis was switched from oxidative phosphorylation-based aerobic metabolism to anaerobic glycolysis, which is an adaption process to satisfy the energy demand for cell survival. Nanospheres with smaller size showed greater capability to alter cellular energy metabolism than those with larger size or nanoplates. Mechanistic investigation manifested that inhibition of PGC-1α by nAg was, at least partially, accountable for the transition from oxidative phosphorylation to glycolysis. Additionally, altered expression of a few energy metabolism-related genes (such as PFKFB3 and PDHA1) was also involved in the transition process. We further showed nAg-induced depolarization of mitochondrial membrane potential and reduction of respiratory chain complex activity. Together, our combined results uncovered the mechanisms by which nAg induced energy metabolism reprogramming in both tumor and nontumor cells under sublethal dosage.
10.1021/nn500719m
Spatial mapping of juxtacrine axo-glial interactions identifies novel molecules in peripheral myelination.
Poitelon Y,Bogni S,Matafora V,Della-Flora Nunes G,Hurley E,Ghidinelli M,Katzenellenbogen B S,Taveggia C,Silvestri N,Bachi A,Sannino A,Wrabetz L,Feltri M L
Nature communications
Cell-cell interactions promote juxtacrine signals in specific subcellular domains, which are difficult to capture in the complexity of the nervous system. For example, contact between axons and Schwann cells triggers signals required for radial sorting and myelination. Failure in this interaction causes dysmyelination and axonal degeneration. Despite its importance, few molecules at the axo-glial surface are known. To identify novel molecules in axo-glial interactions, we modified the 'pseudopodia' sub-fractionation system and isolated the projections that glia extend when they receive juxtacrine signals from axons. By proteomics we identified the signalling networks present at the glial-leading edge, and novel proteins, including members of the Prohibitin family. Glial-specific deletion of Prohibitin-2 in mice impairs axo-glial interactions and myelination. We thus validate a novel method to model morphogenesis and juxtacrine signalling, provide insights into the molecular organization of the axo-glial contact, and identify a novel class of molecules in myelination.
10.1038/ncomms9303
The Phr1 ubiquitin ligase promotes injury-induced axon self-destruction.
Babetto Elisabetta,Beirowski Bogdan,Russler Emilie V,Milbrandt Jeffrey,DiAntonio Aaron
Cell reports
Axon degeneration is an evolutionarily conserved process that drives the loss of damaged axons and is an early event in many neurological disorders, so it is important to identify the molecular constituents of this poorly understood mechanism. Here, we demonstrate that the Phr1 E3 ubiquitin ligase is a central component of this axon degeneration program. Loss of Phr1 results in prolonged survival of severed axons in both the peripheral and central nervous systems, as well as preservation of motor and sensory nerve terminals. Phr1 depletion increases the axonal level of the axon survival molecule nicotinamide mononucleotide adenyltransferase 2 (NMNAT2), and NMNAT2 is necessary for Phr1-dependent axon stability. The profound long-term protection of peripheral and central mammalian axons following Phr1 deletion suggests that pharmacological inhibition of Phr1 function may be an attractive therapeutic candidate for amelioration of axon loss in neurological disease.
10.1016/j.celrep.2013.04.013