scholarly journals Proteolipid domains form in biomimetic and cardiac mitochondrial vesicles and are regulated by cardiolipin concentration but not monolyso-cardiolipin

2018 ◽  
Vol 293 (41) ◽  
pp. 15933-15946 ◽  
Author(s):  
Edward Ross Pennington ◽  
E. Madison Sullivan ◽  
Amy Fix ◽  
Sahil Dadoo ◽  
Tonya N. Zeczycki ◽  
...  
Keyword(s):  
Morphological Changes ◽  
Fluorescent Imaging ◽  
Domain Formation ◽  
Inner Mitochondrial Membrane ◽  
Anionic Phospholipid ◽  
Inner Membrane ◽  
Mixing Properties ◽  
Mitochondrial Inner Membrane ◽  
Acyl Chains ◽  
Underlying Mechanisms

Cardiolipin (CL) is an anionic phospholipid mainly located in the inner mitochondrial membrane, where it helps regulate bioenergetics, membrane structure, and apoptosis. Localized, phase-segregated domains of CL are hypothesized to control mitochondrial inner membrane organization. However, the existence and underlying mechanisms regulating these mitochondrial domains are unclear. Here, we first isolated detergent-resistant cardiac mitochondrial membranes that have been reported to be CL-enriched domains. Experiments with different detergents yielded only nonspecific solubilization of mitochondrial phospholipids, suggesting that CL domains are not recoverable with detergents. Next, domain formation was investigated in biomimetic giant unilamellar vesicles (GUVs) and newly synthesized giant mitochondrial vesicles (GMVs) from mouse hearts. Confocal fluorescent imaging revealed that introduction of cytochrome c into membranes promotes macroscopic proteolipid domain formation associated with membrane morphological changes in both GUVs and GMVs. Domain organization was also investigated after lowering tetralinoleoyl-CL concentration and substitution with monolyso-CL, two common modifications observed in cardiac pathologies. Loss of tetralinoleoyl-CL decreased proteolipid domain formation in GUVs, because of a favorable Gibbs-free energy of lipid mixing, whereas addition of monolyso-CL had no effect on lipid mixing. Moreover, murine GMVs generated from cardiac acyl-CoA synthetase-1 knockouts, which have remodeled CL acyl chains, did not perturb proteolipid domains. Finally, lowering the tetralinoleoyl-CL content had a stronger influence on the oxidation status of cytochrome c than did incorporation of monolyso-CL. These results indicate that proteolipid domain formation in the cardiac mitochondrial inner membrane depends on tetralinoleoyl-CL concentration, driven by underlying lipid-mixing properties, but not the presence of monolyso-CL.

scholarly journals The mitochondrial carrier pathway transports non-canonical substrates with an odd number of transmembrane segments

BMC Biology ◽  
2020 ◽  
Vol 18 (1) ◽  
Author(s):  
Heike Rampelt ◽  
Iva Sucec ◽  
Beate Bersch ◽  
Patrick Horten ◽  
Inge Perschil ◽  
...  
Keyword(s):  
Intermembrane Space ◽  
Inner Mitochondrial Membrane ◽  
Inner Membrane ◽  
Mitochondrial Carrier ◽  
Transmembrane Segments ◽  
Mitochondrial Inner Membrane ◽  
N Terminus ◽  
The Matrix ◽  
Mitochondrial Carrier Family ◽  
Mitochondrial Intermembrane Space

Abstract Background The mitochondrial pyruvate carrier (MPC) plays a central role in energy metabolism by transporting pyruvate across the inner mitochondrial membrane. Its heterodimeric composition and homology to SWEET and semiSWEET transporters set the MPC apart from the canonical mitochondrial carrier family (named MCF or SLC25). The import of the canonical carriers is mediated by the carrier translocase of the inner membrane (TIM22) pathway and is dependent on their structure, which features an even number of transmembrane segments and both termini in the intermembrane space. The import pathway of MPC proteins has not been elucidated. The odd number of transmembrane segments and positioning of the N-terminus in the matrix argues against an import via the TIM22 carrier pathway but favors an import via the flexible presequence pathway. Results Here, we systematically analyzed the import pathways of Mpc2 and Mpc3 and report that, contrary to an expected import via the flexible presequence pathway, yeast MPC proteins with an odd number of transmembrane segments and matrix-exposed N-terminus are imported by the carrier pathway, using the receptor Tom70, small TIM chaperones, and the TIM22 complex. The TIM9·10 complex chaperones MPC proteins through the mitochondrial intermembrane space using conserved hydrophobic motifs that are also required for the interaction with canonical carrier proteins. Conclusions The carrier pathway can import paired and non-paired transmembrane helices and translocate N-termini to either side of the mitochondrial inner membrane, revealing an unexpected versatility of the mitochondrial import pathway for non-cleavable inner membrane proteins.

scholarly journals Mitofilin complexes: conserved organizers of mitochondrial membrane architecture

2012 ◽  
Vol 393 (11) ◽  
pp. 1247-1261 ◽  
Author(s):  
Ralf M. Zerbes ◽  
Ida J. van der Klei ◽  
Marten Veenhuis ◽  
Nikolaus Pfanner ◽  
Martin van der Laan ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Mitochondrial Membrane ◽  
Protein Complexes ◽  
Boundary Region ◽  
Inner Mitochondrial Membrane ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Oligomeric Protein ◽  
Enzyme Complexes ◽  
Boundary Membrane

Abstract Mitofilin proteins are crucial organizers of mitochondrial architecture. They are located in the inner mitochondrial membrane and interact with several protein complexes of the outer membrane, thereby generating contact sites between the two membrane systems of mitochondria. Within the inner membrane, mitofilins are part of hetero-oligomeric protein complexes that have been termed the mitochondrial inner membrane organizing system (MINOS). MINOS integrity is required for the maintenance of the characteristic morphology of the inner mitochondrial membrane, with an inner boundary region closely apposed to the outer membrane and cristae membranes, which form large tubular invaginations that protrude into the mitochondrial matrix and harbor the enzyme complexes of the oxidative phosphorylation machinery. MINOS deficiency comes along with a loss of crista junction structures and the detachment of cristae from the inner boundary membrane. MINOS has been conserved in evolution from unicellular eukaryotes to humans, where alterations of MINOS subunits are associated with multiple pathological conditions.

scholarly journals Elamipretide for Barth syndrome cardiomyopathy: gradual rebuilding of a failed power grid

2021 ◽  
Author(s):  
Hani N. Sabbah
Keyword(s):  
Water Soluble ◽  
Barth Syndrome ◽  
Inner Mitochondrial Membrane ◽  
Cyclic Neutropenia ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Challenges And Opportunities ◽  
Pediatric Cardiomyopathy ◽  
Induced Pluripotent ◽  
Models Of Disease

AbstractBarth syndrome is a rare and potentially fatal X-linked disease characterized by cardiomyopathy, skeletal muscle weakness, growth delays, and cyclic neutropenia. Patients with Barth syndrome are prone to high risk of mortality in infancy and the development of cardiomyopathy with severe weakening of the immune system. Elamipretide is a water-soluble, aromatic-cationic, mitochondria-targeting tetrapeptide that readily penetrates and transiently localizes to the inner mitochondrial membrane. Therapy with elamipretide facilitates cell health by improving energy production and inhibiting excessive formation of reactive oxygen species, thus alleviating oxidative stress. Elamipretide crosses the outer membrane of the mitochondrion and becomes associated with cardiolipin, a constituent phospholipid of the inner membrane. Elamipretide improves mitochondrial bioenergetics and morphology rapidly in induced pluripotent stem cells from patients with Barth syndrome and other genetically related diseases characterized by pediatric cardiomyopathy. Data with elamipretide across multiple models of disease are especially promising, with results from several studies supporting the use of elamipretide as potential therapy for patients with Barth syndrome, particularly where there is a confirmed diagnosis of cardiomyopathy. This review highlights the challenges and opportunities presented in treating Barth syndrome cardiomyopathy patients with elamipretide and addresses evidence supporting the durability of effect of elamipretide as a therapeutic agent for Barth syndrome, especially its likely durable effects on progression of cardiomyopathy following the cessation of drug treatment and the capability of elamipretide to structurally reverse remodel the failing left ventricle at the global, cellular, and molecular level in a gradual manner through specific targeting of the mitochondrial inner membrane.

scholarly journals Atomic structure of the mitochondrial inner membrane AAA+ protease YME1 reveals the mechanism of substrate processing

2017 ◽  
Author(s):  
Cristina Puchades ◽  
Anthony J. Rampello ◽  
Mia Shin ◽  
Christopher J. Giuliano ◽  
R. Luke Wiseman ◽  
...  
Keyword(s):  
Large Scale ◽  
Atp Hydrolysis ◽  
Inner Mitochondrial Membrane ◽  
Inner Membrane ◽  
Conserved Residues ◽  
Mitochondrial Inner Membrane ◽  
Translocation Mechanism ◽  
Substrate Processing ◽  
Aaa Atpases ◽  
Proteolytic Chamber

AbstractWe present the first atomic model of a substrate-bound inner mitochondrial membrane AAA+ quality control protease, YME1. Our ~3.4 Å cryo-EM structure reveals how the ATPases form a closed spiral staircase encircling an unfolded substrate, directing it toward the flat, symmetric protease ring. Importantly, the structure reveals how three coexisting nucleotide states allosterically induce distinct positioning of tyrosines in the central channel, resulting in substrate engagement and translocation to the negatively charged proteolytic chamber. This tight coordination by a network of conserved residues defines a sequential, around-the-ring ATP hydrolysis cycle that results in step-wise substrate translocation. Furthermore, we identify a hinge-like linker that accommodates the large-scale nucleotide-driven motions of the ATPase spiral independently of the contiguous planar proteolytic base. These results define the first molecular mechanism for a mitochondrial inner membrane AAA+ protease and reveal a translocation mechanism likely conserved for other AAA+ ATPases.

scholarly journals MINSTED fluorescence localization and nanoscopy

2021 ◽  
Author(s):  
Michael Weber ◽  
Marcel Leutenegger ◽  
Stefan Stoldt ◽  
Stefan Jakobs ◽  
Tiberiu S. Mihaila ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Super Resolution ◽  
Diffraction Limit ◽  
Stimulated Emission ◽  
Far Field ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Molecular Scale ◽  
Localization Precision ◽  
Super Resolution Microscopy

AbstractWe introduce MINSTED, a fluorophore localization and super-resolution microscopy concept based on stimulated emission depletion (STED) that provides spatial precision and resolution down to the molecular scale. In MINSTED, the intensity minimum of the STED doughnut, and hence the point of minimal STED, serves as a movable reference coordinate for fluorophore localization. As the STED rate, the background and the required number of fluorescence detections are low compared with most other STED microscopy and localization methods, MINSTED entails substantially less fluorophore bleaching. In our implementation, 200–1,000 detections per fluorophore provide a localization precision of 1–3 nm in standard deviation, which in conjunction with independent single fluorophore switching translates to a ~100-fold improvement in far-field microscopy resolution over the diffraction limit. The performance of MINSTED nanoscopy is demonstrated by imaging the distribution of Mic60 proteins in the mitochondrial inner membrane of human cells.

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