| 1. |
- Diessl, Jutta, 1989-, et al.
(författare)
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Manganese-driven CoQ deficiency
- 2022
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Overexposure to manganese disrupts cellular energy metabolism across species, but the molecular mechanism underlying manganese toxicity remains enigmatic. Here, we report that excess cellular manganese selectively disrupts coenzyme Q (CoQ) biosynthesis, resulting in failure of mitochondrial bioenergetics. While respiratory chain complexes remain intact, the lack of CoQ as lipophilic electron carrier precludes oxidative phosphorylation and leads to premature cell and organismal death. At a molecular level, manganese overload causes mismetallation and proteolytic degradation of Coq7, a diiron hydroxylase that catalyzes the penultimate step in CoQ biosynthesis. Coq7 overexpression or supplementation with a CoQ headgroup analog that bypasses Coq7 function fully corrects electron transport, thus restoring respiration and viability. We uncover a unique sensitivity of a diiron enzyme to mismetallation and define the molecular mechanism for manganese-induced bioenergetic failure that is conserved across species. Across phylae, excess manganese disrupts energy metabolism by unclear mechanisms. Here, Diessl et al. report that failure of mitochondrial bioenergetics upon manganese overload is due to mismetallation of a diiron enzyme crucial for CoQ biosynthesis
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| 2. |
- Kohler, Andreas, Dr. rer. nat. 1988-, et al.
(författare)
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Early fate decision for mitochondrially encoded proteins by a molecular triage
- 2023
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Ingår i: Molecular Cell. - : Cell Press. - 1097-2765 .- 1097-4164. ; 83:19
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Tidskriftsartikel (refereegranskat)abstract
- Folding of newly synthesized proteins poses challenges for a functional proteome. Dedicated protein quality control (PQC) systems either promote the folding of nascent polypeptides at ribosomes or, if this fails, ensure their degradation. Although well studied for cytosolic protein biogenesis, it is not understood how these processes work for mitochondrially encoded proteins, key subunits of the oxidative phosphorylation (OXPHOS) system. Here, we identify dedicated hubs in proximity to mitoribosomal tunnel exits coordinating mitochondrial protein biogenesis and quality control. Conserved prohibitin (PHB)/m-AAA protease supercomplexes and the availability of assembly chaperones determine the fate of newly synthesized proteins by molecular triaging. The localization of these competing activities in the vicinity of the mitoribosomal tunnel exit allows for a prompt decision on whether newly synthesized proteins are fed into OXPHOS assembly or are degraded.
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| 3. |
- Berndtsson, Jens, 1989-
(författare)
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Structural and functional studies of protein complexes involved in energy metabolism
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Mitochondria are eukaryotic organelles with a multitude of functions including biosynthesis of molecules and cellular regulation. Most prominently though is their role in energy conversion which culminates with the production of ATP, the universal molecular unit of currency. This is done through several metabolic pathways, including the pyruvate dehydrogenase bridging reaction, the citric acid cycle and the oxidative phosphorylation. In the latter pathway, electrons are transferred from electron carriers formed in the previous pathways and shuttled trough a chain of protein complexes (complex I – complex IV) via the mobile electron carriers coenzyme Q and cytochrome c. Collectively this is known as the respiratory chain. This process harnesses energy from the transferred electrons to translocate protons across the mitochondrial inner membrane, forming an electrochemical gradient that the ATP synthase uses to generate ATP. In this thesis we study parts of these metabolic pathways both structurally and functionally, using a combination of cryo-EM, biochemistry and cell biology. In the first project we used cryo-EM to solve the structure of the pyruvate dehydrogenase complex of E. coli, gaining new insight into how the flexible lipoyl-domain interacts with the active site of the core of the complex. We could determine that this interaction is mediated through electrostatic interaction formed between an acidic patch of amino acids of the lipoyl-domain and positively charged amino acids on the core. In the second project we again employed cryo-EM, this time to solve the structure of the yeast respiratory supercomplex, and for the first time we could obtain a near-atomic resolution structure of how complex III and complex IV in yeast interact with each other to form respiratory supercomplexes. Two forms of these higher order assemblies exist in the respiratory chain of yeast (CIII2/CIV and CIII2/CIV2), which assembles very differently compared to the mammalian CI/CIII2/CIV respirasome. The main interaction point of the yeast supercomplexes occurs between the subunits Cor1 and Cox5a. Through selective point mutations, we were able to disrupt this interaction and effectively hinder supercomplex formation in yeast. Using biochemistry and cell biology on such disrupted cells, we could determine that supercomplexes form to facilitate better diffusion of cytochrome c between the individual complexes of the supercomplex. In the third project we look at how manganese toxicity impacts the respiratory chain in yeast on a molecular level. By combining proteomics, biochemistry and metal analyses, we found that manganese overload causes mismetalation of Coq7, an essential subunit of the coenzyme Q synthesis pathway, which causes a loss of the electron carrier between complex II and complex III. This loss of coenzyme Q could be restored when cells were augmented with Coq7 overexpression, which restored functional respiration and prevented age-related cell death.
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| 4. |
- Olofsson Bagge, Roger, 1978, et al.
(författare)
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Three-dimensional reconstruction of interstitial extracellular vesicles in human liver as determined by electron tomography
- 2023
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Ingår i: Journal of Extracellular Vesicles. - 2001-3078. ; 12:12
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Tidskriftsartikel (refereegranskat)abstract
- Extracellular vesicles (EVs) are lipid bilayer nanoparticles involved in cell-cell communication that are released into the extracellular space by all cell types. The cargo of EVs includes proteins, lipids, nucleic acids, and metabolites reflecting their cell of origin. EVs have recently been isolated directly from solid tissues, and this may provide insights into how EVs mediate communication between cells in vivo. Even though EVs have been isolated from tissues, their point of origin when they are in the interstitial space has been uncertain. In this study, we performed three-dimensional (3D) reconstruction using transmission electron tomography of metastatic and normal liver tissues with a focus on the presence of EVs in the interstitium. After chemical fixation of the samples and subsequent embedding of tissue pieces in resin, ultrathin slices (300 nm) were cut and imaged on a 120 ekV transmission electron microscopy as a tilt series (a series of subsequent images tilted at different angles). These were then computationally illustrated in a 3D manner to reconstruct the imaged tissue volume. We identified the cells delimiting the interstitial space in both types of tissues, and small distinct spherical structures with a diameter of 30-200 nm were identified between the cells. These round structures appeared to be more abundant in metastatic tissue compared to normal tissue. We suggest that the observed spherical structures in the interstitium of the metastatic and non-metastatic liver represent EVs. This work thus provides the first 3D visualization of EVs in human tissue. Three-dimensional (3D) reconstruction of both liver metastases and normal liver, using transmission electron tomography, identified spherical structures with a diameter of 30-200 nm in the interstitium of both types of tissues.image
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| 5. |
- Tidemand Johansen, Nicolai, et al.
(författare)
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Mg2+-dependent conformational equilibria in CorA and an integrated view on transport regulation
- 2022
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Ingår i: eLIFE. - 2050-084X. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- The CorA family of proteins regulates the homeostasis of divalent metal ions in many bacteria, archaea, and eukaryotic mitochondria, making it an important target in the investigation of the mechanisms of transport and its functional regulation. Although numerous structures of open and closed channels are now available for the CorA family, the mechanism of the transport regulation remains elusive. Here, we investigated the conformational distribution and associated dynamic behaviour of the pentameric Mg2+ channel CorA at room temperature using small-angle neutron scattering (SANS) in combination with molecular dynamics (MD) simulations and solid-state nuclear magnetic resonance spectroscopy (NMR). We find that neither the Mg2+-bound closed structure nor the Mg2+-free open forms are sufficient to explain the average conformation of CorA. Our data support the presence of conformational equilibria between multiple states, and we further find a variation in the behaviour of the backbone dynamics with and without Mg2+. We propose that CorA must be in a dynamic equilibrium between different non-conducting states, both symmetric and asymmetric, regardless of bound Mg2+ but that conducting states become more populated in Mg2+-free conditions. These properties are regulated by backbone dynamics and are key to understanding the functional regulation of CorA.
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