scholarly journals Mitochondrial morphology, topology, and membrane interactions in skeletal muscle: a quantitative three-dimensional electron microscopy study

2013 ◽  
Vol 114 (2) ◽  
pp. 161-171 ◽  
Author(s):  
Martin Picard ◽  
Kathryn White ◽  
Douglass M. Turnbull
Keyword(s):  
Electron Microscopy ◽  
Skeletal Muscle ◽  
Mitochondrial Membrane ◽  
Freeze Fracture ◽  
Membrane Dynamics ◽  
Mitochondrial Morphology ◽  
Mitochondrial Membranes ◽  
Intact Mouse ◽  
Mouse Skeletal Muscle

Dynamic remodeling of mitochondrial morphology through membrane dynamics are linked to changes in mitochondrial and cellular function. Although mitochondrial membrane fusion/fission events are frequent in cell culture models, whether mitochondrial membranes dynamically interact in postmitotic muscle fibers in vivo remains unclear. Furthermore, a quantitative assessment of mitochondrial morphology in intact muscle is lacking. Here, using electron microscopy (EM), we provide evidence of interacting membranes from adjacent mitochondria in intact mouse skeletal muscle. Electron-dense mitochondrial contact sites consistent with events of outer mitochondrial membrane tethering are also described. These data suggest that mitochondrial membranes interact in vivo among mitochondria, possibly to induce morphology transitions, for kiss-and-run behavior, or other processes involving contact between mitochondrial membranes. Furthermore, a combination of freeze-fracture scanning EM and transmission EM in orthogonal planes was used to characterize and quantify mitochondrial morphology. Two subpopulations of mitochondria were studied: subsarcolemmal (SS) and intermyofibrillar (IMF), which exhibited significant differences in morphological descriptors, including form factor (means ± SD for SS: 1.41 ± 0.45 vs. IMF: 2.89 ± 1.76, P < 0.01) and aspect ratio (1.97 ± 0.83 vs. 3.63 ± 2.13, P < 0.01) and circularity (0.75 ± 0.16 vs. 0.45 ± 0.22, P < 0.01) but not size (0.28 ± 0.31 vs. 0.27 ± 0.20 μm2). Frequency distributions for mitochondrial size and morphological parameters were highly skewed, suggesting the presence of mechanisms to influence mitochondrial size and shape. In addition, physical continuities between SS and IMF mitochondria indicated mixing of both subpopulations. These data provide evidence that mitochondrial membranes interact in vivo in mouse skeletal muscle and that factors may be involved in regulating skeletal muscle mitochondrial morphology.

scholarly journals Acute exercise remodels mitochondrial membrane interactions in mouse skeletal muscle

2013 ◽  
Vol 115 (10) ◽  
pp. 1562-1571 ◽  
Author(s):  
Martin Picard ◽  
Benoit J. Gentil ◽  
Meagan J. McManus ◽  
Kathryn White ◽  
Kyle St. Louis ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Mammalian Cells ◽  
Mitochondrial Membrane ◽  
Acute Exercise ◽  
Exercise Intervention ◽  
Cultured Cells ◽  
Mitochondrial Dynamics ◽  
Membrane Dynamics ◽  
Mitochondrial Morphology ◽  
Membrane Interactions

A unique property of mitochondria in mammalian cells is their ability to physically interact and undergo dynamic events of fusion/fission that remodel their morphology and possibly their function. In cultured cells, metabolic perturbations similar to those incurred during exercise influence mitochondrial fusion and fission processes, but it is unknown whether exercise acutely alters mitochondrial morphology and/or membrane interactions in vivo. To study this question, we subjected mice to a 3-h voluntarily exercise intervention following their normal physical activity patterns, and quantified mitochondrial morphology and membrane interactions in the soleus using a quantitative electron microscopy approach. A single exercise bout effectively decreased blood glucose ( P < 0.05) and intramyocellular lipid content ( P < 0.01), indicating increased muscle metabolic demand. The number of mitochondria spanning Z-lines and proportion of electron-dense contact sites (EDCS) between adjacent mitochondrial membranes were increased immediately after exercise among both subsarcolemmal (+116%, P < 0.05) and intermyofibrillar mitochondria (+191%, P < 0.001), indicating increased physical interactions. Mitochondrial morphology, and abundance of the mitochondrial pro-fusion proteins Mfn2 and OPA1 were unchanged. Collectively, these results support the notion that mitochondrial membrane dynamics are actively remodelled in skeletal muscle, which may be regulated by contractile activity and the metabolic state. Future studies are required to understand the implications of mitochondrial dynamics in skeletal muscle physiology during exercise and inactivity.

Vitamin E prevents hypobaric hypoxia-induced mitochondrial dysfunction in skeletal muscle

2007 ◽  
Vol 113 (12) ◽  
pp. 459-466 ◽  
Author(s):  
José Magalhães ◽  
Rita Ferreira ◽  
Maria J. Neuparth ◽  
Paulo J. Oliveira ◽  
Franklim Marques ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Vitamin E ◽  
Mitochondrial Dysfunction ◽  
Hypobaric Hypoxia ◽  
Mitochondrial Membrane ◽  
Mitochondrial Protein ◽  
Membrane Integrity ◽  
Outer Mitochondrial Membrane ◽  
Hypoxia Exposure

In the present study, the effect of vitamin E (α-tocopherol) on mice skeletal muscle mitochondrial dysfunction and oxidative damage induced by an in vivo acute and severe hypobaric hypoxic insult (48 h at a barometric pressure equivalent to 8500 m) has been investigated. Male mice (n=24) were randomly divided into the following four groups (n=6): control (C), hypoxia (H), vitamin E (VE; 60 mg/kg of body weight intraperitoneally, three times/week for 3 weeks) and hypoxia+VE (HVE). A significant increase in mitochondrial protein CGs (carbonyl groups) was found in the H group compared with the C group. Confirming previous observations from our group, hypoxia induced mitochondrial dysfunction, as identified by altered respiratory parameters. Hypoxia exposure increased Bax content and decreased the Bcl-2/Bax ratio, whereas Bcl-2 remained unchanged. Inner and outer mitochondrial membrane integrity were significantly affected by hypoxia exposure; however, vitamin E treatment attenuated the effect of hypoxia on mitochondrial oxidative phosphorylation and on the levels of CGs. Vitamin E supplementation also prevented the Bax and Bcl-2/Bax ratio impairments caused by hypoxia, as well as the decrease in inner and outer mitochondrial membrane integrity. In conclusion, the results suggest that vitamin E prevents the loss of mitochondrial integrity and function, as well as the increase in Bax content, which suggests that mitochondria are involved in increased cell death induced by severe hypobaric hypoxia in mice skeletal muscle.

Dynamic organization of the mitochondrial protein import machinery

2016 ◽  
Vol 397 (11) ◽  
pp. 1097-1114 ◽  
Author(s):  
Sebastian P. Straub ◽  
Sebastian B. Stiller ◽  
Nils Wiedemann ◽  
Nikolaus Pfanner
Keyword(s):  
Mitochondrial Membrane ◽  
Protein Import ◽  
Mitochondrial Protein ◽  
Membrane Dynamics ◽  
Intermembrane Space ◽  
Mitochondrial Protein Import ◽  
Precursor Proteins ◽  
Dynamic Cooperation

Abstract Mitochondria contain elaborate machineries for the import of precursor proteins from the cytosol. The translocase of the outer mitochondrial membrane (TOM) performs the initial import of precursor proteins and transfers the precursors to downstream translocases, including the presequence translocase and the carrier translocase of the inner membrane, the mitochondrial import and assembly machinery of the intermembrane space, and the sorting and assembly machinery of the outer membrane. Although the protein translocases can function as separate entities in vitro, recent studies revealed a close and dynamic cooperation of the protein import machineries to facilitate efficient transfer of precursor proteins in vivo. In addition, protein translocases were found to transiently interact with distinct machineries that function in the respiratory chain or in the maintenance of mitochondrial membrane architecture. Mitochondrial protein import is embedded in a regulatory network that ensures protein biogenesis, membrane dynamics, bioenergetic activity and quality control.

scholarly journals Mitochondrial Membrane Dynamics—Functional Positioning of OPA1

Antioxidants ◽  
2018 ◽  
Vol 7 (12) ◽  
pp. 186 ◽  
Author(s):  
Hakjoo Lee ◽  
Yisang Yoon
Keyword(s):  
Mitochondrial Membrane ◽  
Proteolytic Cleavage ◽  
Membrane Dynamics ◽  
Mitochondrial Morphology ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Functional Differences ◽  
New Information ◽  
New Development

The maintenance of mitochondrial energetics requires the proper regulation of mitochondrial morphology, and vice versa. Mitochondrial dynamins control mitochondrial morphology by mediating fission and fusion. One of them, optic atrophy 1 (OPA1), is the mitochondrial inner membrane remodeling protein. OPA1 has a dual role in maintaining mitochondrial morphology and energetics through mediating inner membrane fusion and maintaining the cristae structure. OPA1 is expressed in multiple variant forms through alternative splicing and post-translational proteolytic cleavage, but the functional differences between these variants have not been completely understood. Recent studies generated new information regarding the role of OPA1 cleavage. In this review, we will first provide a brief overview of mitochondrial membrane dynamics by describing fission and fusion that are mediated by mitochondrial dynamins. The second part describes OPA1-mediated fusion and energetic maintenance, the role of OPA1 cleavage, and a new development in OPA1 function, in which we will provide new insight for what OPA1 does and what proteolytic cleavage of OPA1 is for.

MRI imaging for in vivo free radicals and bioenergetics in mouse skeletal muscle

2018 ◽  
Vol 128 ◽  
pp. S123
Author(s):  
Bumsoo Ahn ◽  
Nataliya Smith ◽  
Debra Saunders ◽  
Holly Van Remmen ◽  
Rheal Towner
Keyword(s):  
Skeletal Muscle ◽  
Free Radicals ◽  
Mri Imaging ◽  
Mouse Skeletal Muscle

Cationic Liposome-DNA Complexes: Polymorphism versus Transfection Activity

2000 ◽  
Vol 6 (S2) ◽  
pp. 854-855
Author(s):  
B. Sternberg-Papahadjopoulos ◽  
K. Hong ◽  
W. Zheng ◽  
D. Papahadjopoulos
Keyword(s):  
Electron Microscopy ◽  
Cultured Cells ◽  
Freeze Fracture ◽  
Cationic Liposome ◽  
Specific Structure ◽  
Spherical Particles ◽  
Cubic Phase ◽  
Active Structure

Complexes formed during interaction of cationic liposomes with polynucleotides such as DNA (CLDC) self-assemble into a variety of polymorphic structures. They display bilayer (FIG. 1-5) and non-bilayer structures (FIG. 6). We have recorded bilayer structures such as spaghetti/meatball-type structures (FIG. I), map-pins (FIG. 2) spherical particles and invaginated liposomes (FIG. 3, 4) and oligolamellar structures (FIG. 5). The non-bilayer lipid arrangements include honeycombtype structure (Hn, FIG. 6) and cubic phase lipids.We have chosen mainly freeze-fracture electron microscopy (FIG. 1-3, 5,6) but also cryo-electron microscopy (FIG.4) for recording polymorphic structures, and for studying factors and conditions triggering the formation and stabilization of specific structure types. Furthermore, we took microscopically snapshots of the interaction of specific structure types with cultured cells. In order to find out the “active” structure in terms of transfection, we investigated the transfection activity both in vivo and in vitro of CLDC, and studied in parallel their morphology in serum as well as in cell medium.

scholarly journals Endophilin B1 is required for the maintenance of mitochondrial morphology

2004 ◽  
Vol 166 (7) ◽  
pp. 1027-1039 ◽  
Author(s):  
Mariusz Karbowski ◽  
Seon-Yong Jeong ◽  
Richard J. Youle
Keyword(s):  
Mitochondrial Membrane ◽  
Fatty Acyl ◽  
Membrane Dynamics ◽  
Mitochondrial Morphology ◽  
Outer Mitochondrial Membrane ◽  
Mitochondrial Network ◽  
Truncated Protein ◽  
The Matrix ◽  
Membrane Compartment ◽  
Mitochondrial Distribution

We report that a fatty acyl transferase, endophilin B1, is required for maintenance of mitochondrial morphology. Down-regulation of this protein or overexpression of endophilin B1 lacking the NH2-terminal lipid-modifying domain causes striking alterations of the mitochondrial distribution and morphology. Dissociation of the outer mitochondrial membrane compartment from that of the matrix, and formation of vesicles and tubules of outer mitochondrial membrane, was also observed in both endophilin B1 knockdown cells and after overexpression of the truncated protein, indicating that endophilin B1 is required for the regulation of the outer mitochondrial membrane dynamics. We also show that endophilin B1 translocates to the mitochondria during the synchronous remodeling of the mitochondrial network that has been described to occur during apoptosis. Double knockdown of endophilin B1 and Drp1 leads to a mitochondrial phenotype identical to that of the Drp1 single knockdown, a result consistent with Drp1 acting upstream of endophilin B1 in the maintenance of morphological dynamics of mitochondria.

scholarly journals Preparation and morphology of sarcoplasmic reticulum terminal cisternae from rabbit skeletal muscle.

1984 ◽  
Vol 99 (3) ◽  
pp. 875-885 ◽  
Author(s):  
A Saito ◽  
S Seiler ◽  
A Chu ◽  
S Fleischer
Keyword(s):  
Electron Microscopy ◽  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Thin Section ◽  
Membrane Surface ◽  
Freeze Fracture ◽  
Morphological Characteristics ◽  
Negative Staining ◽  
Section Electron ◽  
Terminal Cisternae

We have developed a procedure to isolate, from skeletal muscle, enriched terminal cisternae of sarcoplasmic reticulum (SR), which retain morphologically intact junctional "feet" structures similar to those observed in situ. The fraction is largely devoid of transverse tubule, plasma membrane, mitochondria, triads (transverse tubules junctionally associated with terminal cisternae), and longitudinal cisternae, as shown by thin-section electron microscopy of representative samples. The terminal cisternae vesicles have distinctive morphological characteristics that differ from the isolated longitudinal cisternae (light SR) obtained from the same gradient. The terminal cisternae consist of two distinct types of membranes, i.e., the junctional face membrane and the Ca2+ pump protein-containing membrane, whereas the longitudinal cisternae contain only the Ca2+ pump protein-containing membrane. The junctional face membrane of the terminal cisternae contains feet structures that extend approximately 12 nm from the membrane surface and can be clearly visualized in thin section through using tannic acid enhancement, by negative staining and by freeze-fracture electron microscopy. Sections of the terminal cisternae, cut tangential to and intersecting the plane of the junctional face, reveal a checkerboardlike lattice of alternating, square-shaped feet structures and spaces each 20 nm square. Structures characteristic of the Ca2+ pump protein are not observed between the feet at the junctional face membrane, either in thin section or by negative staining, even though the Ca2+ pump protein is observed in the nonjunctional membrane on the remainder of the same vesicle. Likewise, freeze-fracture replicas reveal regions of the P face containing ropelike strands instead of the high density of the 7-8-nm particles referable to the Ca2+ pump protein. The intravesicular content of the terminal cisternae, mostly Ca2+-binding protein (calsequestrin), is organized in the form of strands, sometimes appearing paracrystalline, and attached to the inner face of the membrane in the vicinity of the junctional feet. The terminal cisternae preparation is distinct from previously described heavy SR fractions in that it contains the highest percentage of junctional face membrane with morphologically well-preserved junctional feet structures.

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