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.

scholarly journals Selective and Reversible Disruption of Mitochondrial Inner Membrane Protein Complexes by Lipophilic Cations

2021 ◽  
Author(s):  
Anezka Kafkova ◽  
Lisa Tilokani ◽  
Filip Trčka ◽  
Veronika Šrámková ◽  
Marie Vancová ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Respiratory Chain ◽  
Mitochondrial Membrane ◽  
Mitochondrial Morphology ◽  
Respiratory Chain Complexes ◽  
Inner Membrane ◽  
Protein Levels ◽  
Mitochondrial Inner Membrane ◽  
Chain Complexes ◽  
The Impact

ABSTRACTMitochondria represent an attractive drug target in the treatment of many diseases. One of the most commonly used approaches to deliver therapeutics specifically into mitochondria is their conjugation to the triphenylphosphonium (TPP) moiety. While the TPP molecule is often regarded as biologically inert, there is evidence that the moiety itself has a significant impact on the activity of mitochondrial respiratory chain complexes.We studied the impact of a subchronic exposure of C2C12 mouse myoblasts to a set of TPP derivatives. Our results show that the alkyl-TPP cause dose- and hydrophobicity-dependent alterations of mitochondrial morphology and a selective decrease in the amounts of mitochondrial inner membrane (but not outer membrane) proteins including structural subunits of the respiratory chain complexes (such as MT-CO1 of complex IV or NDUFB8 of complex I), as well as components of the mitochondrial calcium uniporter complex (MCUC). The treatment with alkyl-TPP additionally resulted in OPA1-cleavage. Both the structural and functional effects of alkyl-TPP were found to be reversible. A similar effect was observed with the mitochondria-targeted antioxidant MitoQ. We further show that this effect on protein levels cannot be explained solely by a decrease in mitochondrial membrane potential.We conclude that TPP derivatives negatively affect mitochondrial structure and function at least in part through their effect on selective mitochondrial membrane protein levels via a reversible controlled process.

Emerging roles of mitochondrial membrane dynamics in health and disease

2009 ◽  
Vol 390 (8) ◽  
Author(s):  
Anja Schäfer ◽  
Andreas S. Reichert
Keyword(s):  
Quality Control ◽  
Molecular Basis ◽  
Mitochondrial Membrane ◽  
Mitochondrial Dynamics ◽  
Physiological Role ◽  
Membrane Dynamics ◽  
Mitochondrial Morphology ◽  
Mitochondrial Quality Control ◽  
Health And Disease

Abstract Mitochondria are highly dynamic organelles forming a tubular network that is sustained by fusion and fission events. Impairment thereof leads to various neuropathies in humans, such as optic atrophy and Parkinson's disease. We have only begun to understand the molecular machineries facilitating fusion and fission of mitochondria and how these processes are regulated. The physiological role of mitochondrial dynamics and how it may be involved in maintaining mitochondrial functionality is still unclear. Here, we discuss current views in this emerging field focusing on the molecular basis of how mitochondrial morphology is regulated and how this may contribute to mitochondrial quality control.

scholarly journals Role of mitochondrial inner membrane organizing system in protein biogenesis of the mitochondrial outer membrane

2012 ◽  
Vol 23 (20) ◽  
pp. 3948-3956 ◽  
Author(s):  
Maria Bohnert ◽  
Lena-Sophie Wenz ◽  
Ralf M. Zerbes ◽  
Susanne E. Horvath ◽  
David A. Stroud ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Early Stage ◽  
Outer Membrane Proteins ◽  
Mitochondrial Outer Membrane ◽  
Large Core ◽  
Large Protein ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Protein Biogenesis

Mitochondria contain two membranes, the outer membrane and the inner membrane with folded cristae. The mitochondrial inner membrane organizing system (MINOS) is a large protein complex required for maintaining inner membrane architecture. MINOS interacts with both preprotein transport machineries of the outer membrane, the translocase of the outer membrane (TOM) and the sorting and assembly machinery (SAM). It is unknown, however, whether MINOS plays a role in the biogenesis of outer membrane proteins. We have dissected the interaction of MINOS with TOM and SAM and report that MINOS binds to both translocases independently. MINOS binds to the SAM complex via the conserved polypeptide transport–associated domain of Sam50. Mitochondria lacking mitofilin, the large core subunit of MINOS, are impaired in the biogenesis of β-barrel proteins of the outer membrane, whereas mutant mitochondria lacking any of the other five MINOS subunits import β-barrel proteins in a manner similar to wild-type mitochondria. We show that mitofilin is required at an early stage of β-barrel biogenesis that includes the initial translocation through the TOM complex. We conclude that MINOS interacts with TOM and SAM independently and that the core subunit mitofilin is involved in biogenesis of outer membrane β-barrel proteins.

scholarly journals The J-related Segment of Tim44 Is Essential for Cell Viability: A Mutant Tim44 Remains in the Mitochondrial Import Site, but Inefficiently Recruits mtHsp70 and Impairs Protein Translocation

1999 ◽  
Vol 145 (5) ◽  
pp. 961-972 ◽  
Author(s):  
Alessio Merlin ◽  
Wolfgang Voos ◽  
Ammy C. Maarse ◽  
Michiel Meijer ◽  
Nikolaus Pfanner ◽  
...  
Keyword(s):  
Protein Import ◽  
Protein Translocation ◽  
Adaptor Protein ◽  
Dependent Manner ◽  
Wild Type ◽  
Yeast Saccharomyces Cerevisiae ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
J Proteins

Tim44 is a protein of the mitochondrial inner membrane and serves as an adaptor protein for mtHsp70 that drives the import of preproteins in an ATP-dependent manner. In this study we have modified the interaction of Tim44 with mtHsp70 and characterized the consequences for protein translocation. By deletion of an 18-residue segment of Tim44 with limited similarity to J-proteins, the binding of Tim44 to mtHsp70 was weakened. We found that in the yeast Saccharomyces cerevisiae the deletion of this segment is lethal. To investigate the role of the 18-residue segment, we expressed Tim44Δ18 in addition to the endogenous wild-type Tim44. Tim44Δ18 is correctly targeted to mitochondria and assembles in the inner membrane import site. The coexpression of Tim44Δ18 together with wild-type Tim44, however, does not stimulate protein import, but reduces its efficiency. In particular, the promotion of unfolding of preproteins during translocation is inhibited. mtHsp70 is still able to bind to Tim44Δ18 in an ATP-regulated manner, but the efficiency of interaction is reduced. These results suggest that the J-related segment of Tim44 is needed for productive interaction with mtHsp70. The efficient cooperation of mtHsp70 with Tim44 facilitates the translocation of loosely folded preproteins and plays a crucial role in the import of preproteins which contain a tightly folded domain.

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 Two Intermembrane Space Tim Complexes Interact with Different Domains of Tim23p during Its Import into Mitochondria

2000 ◽  
Vol 150 (6) ◽  
pp. 1271-1282 ◽  
Author(s):  
Alison J. Davis ◽  
Naresh B. Sepuri ◽  
Jason Holder ◽  
Arthur E. Johnson ◽  
Robert E. Jensen
Keyword(s):  
Protein Complexes ◽  
Intermediate Stage ◽  
Terminal Segment ◽  
Mitochondrial Outer Membrane ◽  
Cross Linking ◽  
Intermembrane Space ◽  
Cross Link ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane

Tim23p (translocase of the inner membrane) is an essential import component located in the mitochondrial inner membrane. To determine how the Tim23 protein itself is transported into mitochondria, we used chemical cross-linking to identify proteins adjacent to Tim23p during its biogenesis. In the absence of an inner membrane potential, Tim23p is translocated across the mitochondrial outer membrane, but not inserted into the inner membrane. At this intermediate stage, we find that Tim23p forms cross-linked products with two distinct protein complexes of the intermembrane space, Tim8p–Tim13p and Tim9p–Tim10p. Tim9p and Tim10p cross-link to the COOH-terminal domain of the Tim23 protein, which carries all of the targeting signals for Tim23p. Therefore, our results suggest that the Tim9p–Tim10p complex plays a key role in Tim23p import. In contrast, Tim8p and Tim13p cross-link to the hydrophilic NH2-terminal segment of Tim23p, which does not carry essential import information and, thus, the role of Tim8p–Tim13p is unclear. Tim23p contains two matrix-facing, positively charged loops that are essential for its insertion into the inner membrane. The positive charges are not required for interaction with the Tim9p–Tim10p complex, but are essential for cross-linking of Tim23p to components of the inner membrane insertion machinery, including Tim54p, Tim22p, and Tim12p.

scholarly journals Functional Analysis of Subunit e of the F1Fo-ATP Synthase of the Yeast Saccharomyces cerevisiae: Importance of the N-Terminal Membrane Anchor Region

2005 ◽  
Vol 4 (2) ◽  
pp. 346-355 ◽  
Author(s):  
Valerie Everard-Gigot ◽  
Cory D. Dunn ◽  
Brigid M. Dolan ◽  
Susanne Brunner ◽  
Robert E. Jensen ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Atp Synthase ◽  
Mitochondrial Membrane ◽  
Critical Role ◽  
Coiled Coil ◽  
Mitochondrial Morphology ◽  
Hydrophobic Region ◽  
Inner Membrane ◽  
E Protein ◽  
Subunit E

ABSTRACT Mitochondrial F1Fo-ATP synthase complexes do not exist as physically independent entities but rather form dimeric and possibly oligomeric complexes in the inner mitochondrial membrane. Stable dimerization of two F1Fo-monomeric complexes involves the physical association of two membrane-embedded Fo-sectors. Previously, formation of the ATP synthase dimeric-oligomeric network was demonstrated to play a critical role in modulating the morphology of the mitochondrial inner membrane. In Saccharomyces cerevisiae, subunit e (Su e) of the Fo-sector plays a central role in supporting ATP synthase dimerization. The Su e protein is anchored to the inner membrane via a hydrophobic region located at its N-terminal end. The hydrophilic C-terminal region of Su e resides in the intermembrane space and contains a conserved coiled-coil motif. In the present study, we focused on characterizing the importance of these regions for the function of Su e. We created a number of C-terminal-truncated derivatives of the Su e protein and expressed them in the Su e null yeast mutant. Mitochondria were isolated from the resulting transformant strains, and a number of functions of Su e were analyzed. Our results indicate that the N-terminal hydrophobic region plays important roles in the Su e-dependent processes of mitochondrial DNA maintenance, modulation of mitochondrial morphology, and stabilization of the dimer-specific Fo subunits, subunits g and k. Furthermore, we show that the C-terminal coiled-coil region of Su e functions to stabilize the dimeric form of detergent-solubilized ATP synthase complexes. Finally, we propose a model to explain how Su e supports the assembly of the ATP synthase dimers-oligomers in the mitochondrial membrane.

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