scholarly journals The Mia40/CHCHD4 Oxidative Folding System: Redox Regulation and Signaling in the Mitochondrial Intermembrane Space

Antioxidants ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 592
Author(s):  
Eleanor Dickson-Murray ◽  
Kenza Nedara ◽  
Nazanine Modjtahedi ◽  
Kostas Tokatlidis
Keyword(s):  
Redox Regulation ◽  
Protein Import ◽  
Electron Transfer Reaction ◽  
Human Cells ◽  
Human Diseases ◽  
Cell Physiology ◽  
Redox Processes ◽  
Intermembrane Space ◽  
Oxidative Folding ◽  
Mitochondrial Proteome

Mitochondria are critical for several cellular functions as they control metabolism, cell physiology, and cell death. The mitochondrial proteome consists of around 1500 proteins, the vast majority of which (about 99% of them) are encoded by nuclear genes, with only 13 polypeptides in human cells encoded by mitochondrial DNA. Therefore, it is critical for all the mitochondrial proteins that are nuclear-encoded to be targeted precisely and sorted specifically to their site of action inside mitochondria. These processes of targeting and sorting are catalysed by protein translocases that operate in each one of the mitochondrial sub-compartments. The main protein import pathway for the intermembrane space (IMS) recognises proteins that are cysteine-rich, and it is the only import pathway that chemically modifies the imported precursors by introducing disulphide bonds to them. In this manner, the precursors are trapped in the IMS in a folded state. The key component of this pathway is Mia40 (called CHCHD4 in human cells), which itself contains cysteine motifs and is subject to redox regulation. In this review, we detail the basic components of the MIA pathway and the disulphide relay mechanism that underpins the electron transfer reaction along the oxidative folding mechanism. Then, we discuss the key protein modulators of this pathway and how they are interlinked to the small redox-active molecules that critically affect the redox state in the IMS. We present also evidence that the mitochondrial redox processes that are linked to iron–sulfur clusters biogenesis and calcium homeostasis coalesce in the IMS at the MIA machinery. The fact that the MIA machinery and several of its interactors and substrates are linked to a variety of common human diseases connected to mitochondrial dysfunction highlight the potential of redox processes in the IMS as a promising new target for developing new treatments for some of the most complex and devastating human diseases.

scholarly journals Mutant huntingtin disrupts mitochondrial proteostasis by interacting with TIM23

2019 ◽  
Vol 116 (33) ◽  
pp. 16593-16602 ◽  
Author(s):  
Svitlana Yablonska ◽  
Vinitha Ganesan ◽  
Lisa M. Ferrando ◽  
JinHo Kim ◽  
Anna Pyzel ◽  
...  
Keyword(s):  
Cell Lines ◽  
Protein Import ◽  
Mitochondrial Protein ◽  
Biological Significance ◽  
Intermembrane Space ◽  
Mutant Huntingtin ◽  
Mitochondrial Protein Import ◽  
Inner Membrane ◽  
Mitochondrial Proteome ◽  
Brain Tissues

Mutant huntingtin (mHTT), the causative protein in Huntington’s disease (HD), associates with the translocase of mitochondrial inner membrane 23 (TIM23) complex, resulting in inhibition of synaptic mitochondrial protein import first detected in presymptomatic HD mice. The early timing of this event suggests that it is a relevant and direct pathophysiologic consequence of mHTT expression. We show that, of the 4 TIM23 complex proteins, mHTT specifically binds to the TIM23 subunit and that full-length wild-type huntingtin (wtHTT) and mHTT reside in the mitochondrial intermembrane space. We investigated differences in mitochondrial proteome between wtHTT and mHTT cells and found numerous proteomic disparities between mHTT and wtHTT mitochondria. We validated these data by quantitative immunoblotting in striatal cell lines and human HD brain tissue. The level of soluble matrix mitochondrial proteins imported through the TIM23 complex is lower in mHTT-expressing cell lines and brain tissues of HD patients compared with controls. In mHTT-expressing cell lines, membrane-bound TIM23-imported proteins have lower intramitochondrial levels, whereas inner membrane multispan proteins that are imported via the TIM22 pathway and proteins integrated into the outer membrane generally remain unchanged. In summary, we show that, in mitochondria, huntingtin is located in the intermembrane space, that mHTT binds with high-affinity to TIM23, and that mitochondria from mHTT-expressing cells and brain tissues of HD patients have reduced levels of nuclearly encoded proteins imported through TIM23. These data demonstrate the mechanism and biological significance of mHTT-mediated inhibition of mitochondrial protein import, a mechanism likely broadly relevant to other neurodegenerative diseases.

scholarly journals The mitochondrial intermembrane space: the most constricted mitochondrial sub-compartment with the largest variety of protein import pathways

Open Biology ◽  
2021 ◽  
Vol 11 (3) ◽  
Author(s):  
Ruairidh Edwards ◽  
Ross Eaglesfield ◽  
Kostas Tokatlidis
Keyword(s):  
Protein Import ◽  
Atp Hydrolysis ◽  
Current Knowledge ◽  
Intermembrane Space ◽  
Inner Membrane ◽  
Mitochondrial Proteome ◽  
Normal Site ◽  
The Matrix ◽  
Human Disorders ◽  
Mitochondrial Intermembrane Space

The mitochondrial intermembrane space (IMS) is the most constricted sub-mitochondrial compartment, housing only about 5% of the mitochondrial proteome, and yet is endowed with the largest variability of protein import mechanisms. In this review, we summarize our current knowledge of the major IMS import pathway based on the oxidative protein folding pathway and discuss the stunning variability of other IMS protein import pathways. As IMS-localized proteins only have to cross the outer mitochondrial membrane, they do not require energy sources like ATP hydrolysis in the mitochondrial matrix or the inner membrane electrochemical potential which are critical for import into the matrix or insertion into the inner membrane. We also explore several atypical IMS import pathways that are still not very well understood and are guided by poorly defined or completely unknown targeting peptides. Importantly, many of the IMS proteins are linked to several human diseases, and it is therefore crucial to understand how they reach their normal site of function in the IMS. In the final part of this review, we discuss current understanding of how such IMS protein underpin a large spectrum of human disorders.

scholarly journals Protein import and oxidative folding in the mitochondrial intermembrane space of intact mammalian cells

2013 ◽  
Vol 24 (14) ◽  
pp. 2160-2170 ◽  
Author(s):  
Manuel Fischer ◽  
Sebastian Horn ◽  
Anouar Belkacemi ◽  
Kerstin Kojer ◽  
Carmelina Petrungaro ◽  
...  
Keyword(s):  
Protein Oxidation ◽  
Mammalian Cells ◽  
Protein Import ◽  
Mitochondrial Protein ◽  
Intermembrane Space ◽  
Basic Principles ◽  
Oxidative Folding ◽  
Physiological Conditions ◽  
Mitochondrial Intermembrane Space ◽  
Kinetics Of

Oxidation of cysteine residues to disulfides drives import of many proteins into the intermembrane space of mitochondria. Recent studies in yeast unraveled the basic principles of mitochondrial protein oxidation, but the kinetics under physiological conditions is unknown. We developed assays to follow protein oxidation in living mammalian cells, which reveal that import and oxidative folding of proteins are kinetically and functionally coupled and depend on the oxidoreductase Mia40, the sulfhydryl oxidase augmenter of liver regeneration (ALR), and the intracellular glutathione pool. Kinetics of substrate oxidation depends on the amount of Mia40 and requires tightly balanced amounts of ALR. Mia40-dependent import of Cox19 in human cells depends on the inner membrane potential. Our observations reveal considerable differences in the velocities of mitochondrial import pathways: whereas preproteins with bipartite targeting sequences are imported within seconds, substrates of Mia40 remain in the cytosol for several minutes and apparently escape premature degradation and oxidation.

scholarly journals Mitochondrial protein import: Mia40 facilitates Tim22 translocation into the inner membrane of mitochondria

2013 ◽  
Vol 24 (5) ◽  
pp. 543-554 ◽  
Author(s):  
Lidia Wrobel ◽  
Agata Trojanowska ◽  
Malgorzata E. Sztolsztener ◽  
Agnieszka Chacinska
Keyword(s):  
Disulfide Bonds ◽  
Protein Import ◽  
Noncovalent Interactions ◽  
Mitochondrial Protein ◽  
Central Component ◽  
Intermembrane Space ◽  
Mitochondrial Protein Import ◽  
Inner Membrane ◽  
Oxidative Folding ◽  
Mitochondrial Intermembrane Space

The mitochondrial intermembrane space assembly (MIA) pathway is generally considered to be dedicated to the redox-dependent import and biogenesis of proteins localized to the intermembrane space of mitochondria. The oxidoreductase Mia40 is a central component of the pathway responsible for the transfer of disulfide bonds to intermembrane space precursor proteins, causing their oxidative folding. Here we present the first evidence that the function of Mia40 is not restricted to the transport and oxidative folding of intermembrane space proteins. We identify Tim22, a multispanning membrane protein and core component of the TIM22 translocase of inner membrane, as a protein with cysteine residues undergoing oxidation during Tim22 biogenesis. We show that Mia40 is involved in the biogenesis and complex assembly of Tim22. Tim22 forms a disulfide-bonded intermediate with Mia40 upon import into mitochondria. Of interest, Mia40 binds the Tim22 precursor also via noncovalent interactions. We propose that Mia40 not only is responsible for disulfide bond formation, but also assists the Tim22 protein in its integration into the inner membrane of mitochondria.

Oxidative folding: recent developments

2011 ◽  
Vol 2 (5) ◽  
pp. 379-390 ◽  
Author(s):  
András Szarka ◽  
Gábor Bánhegyi
Keyword(s):  
Endoplasmic Reticulum ◽  
Disulfide Bonds ◽  
Redox Regulation ◽  
Disulfide Bridge ◽  
Intermembrane Space ◽  
Redox Systems ◽  
Oxidative Folding ◽  
Recent Developments ◽  
Mitochondrial Intermembrane Space ◽  
Structure Stabilization

AbstractDisulfide bond formation in proteins is an effective tool of both structure stabilization and redox regulation. The prokaryotic periplasm and the endoplasmic reticulum of eukaryotes were long considered as the only compartments for enzyme mediated formation of stable disulfide bonds. Recently, the mitochondrial intermembrane space has emerged as the third protein-oxidizing compartment. The classic view on the mechanism of oxidative folding in the endoplasmic reticulum has also been reshaped by new observations. Moreover, besides the structure stabilizing function, reversible disulfide bridge formation in some proteins of the endoplasmic reticulum, seems to play a regulatory role. This review briefly summarizes the present knowledge of the redox systems supporting oxidative folding, emphasizing recent developments.

scholarly journals Kinetic control by limiting glutaredoxin amounts enables thiol oxidation in the reducing mitochondrial intermembrane space

2015 ◽  
Vol 26 (2) ◽  
pp. 195-204 ◽  
Author(s):  
Kerstin Kojer ◽  
Valentina Peleh ◽  
Gaetano Calabrese ◽  
Johannes M. Herrmann ◽  
Jan Riemer
Keyword(s):  
Redox State ◽  
Protein Import ◽  
Kinetic Control ◽  
Intermembrane Space ◽  
Mitochondrial Import ◽  
Oxidative Folding ◽  
Mitochondrial Intermembrane Space ◽  
Reducing Environment ◽  
Targeting Signals ◽  
Main Component

The mitochondrial intermembrane space (IMS) harbors an oxidizing machinery that drives import and folding of small cysteine-containing proteins without targeting signals. The main component of this pathway is the oxidoreductase Mia40, which introduces disulfides into its substrates. We recently showed that the IMS glutathione pool is maintained as reducing as that of the cytosol. It thus remained unclear how equilibration of protein disulfides with the IMS glutathione pool is prevented in order to allow oxidation-driven protein import. Here we demonstrate the presence of glutaredoxins in the IMS and show that limiting amounts of these glutaredoxins provide a kinetic barrier to prevent the thermodynamically feasible reduction of Mia40 substrates by the IMS glutathione pool. Moreover, they allow Mia40 to exist in a predominantly oxidized state. Consequently, overexpression of glutaredoxin 2 in the IMS results in a more reduced Mia40 redox state and a delay in oxidative folding and mitochondrial import of different Mia40 substrates. Our findings thus indicate that carefully balanced glutaredoxin amounts in the IMS ensure efficient oxidative folding in the reducing environment of this compartment.

scholarly journals Redox-Mediated Regulation of Mitochondrial Biogenesis, Dynamics, and Respiratory Chain Assembly in Yeast and Human Cells

2021 ◽  
Vol 9 ◽  
Author(s):  
Stefan Geldon ◽  
Erika Fernández-Vizarra ◽  
Kostas Tokatlidis
Keyword(s):  
Redox Regulation ◽  
Redox Balance ◽  
Cellular Respiration ◽  
Ros Generation ◽  
Intermembrane Space ◽  
Oxidation Reactions ◽  
Complex Iv ◽  
Inner Membrane ◽  
Mitochondrial Proteome ◽  
The Matrix

Mitochondria are double-membrane organelles that contain their own genome, the mitochondrial DNA (mtDNA), and reminiscent of its endosymbiotic origin. Mitochondria are responsible for cellular respiration via the function of the electron oxidative phosphorylation system (OXPHOS), located in the mitochondrial inner membrane and composed of the four electron transport chain (ETC) enzymes (complexes I-IV), and the ATP synthase (complex V). Even though the mtDNA encodes essential OXPHOS components, the large majority of the structural subunits and additional biogenetical factors (more than seventy proteins) are encoded in the nucleus and translated in the cytoplasm. To incorporate these proteins and the rest of the mitochondrial proteome, mitochondria have evolved varied, and sophisticated import machineries that specifically target proteins to the different compartments defined by the two membranes. The intermembrane space (IMS) contains a high number of cysteine-rich proteins, which are mostly imported via the MIA40 oxidative folding system, dependent on the reduction, and oxidation of key Cys residues. Several of these proteins are structural components or assembly factors necessary for the correct maturation and function of the ETC complexes. Interestingly, many of these proteins are involved in the metalation of the active redox centers of complex IV, the terminal oxidase of the mitochondrial ETC. Due to their function in oxygen reduction, mitochondria are the main generators of reactive oxygen species (ROS), on both sides of the inner membrane, i.e., in the matrix and the IMS. ROS generation is important due to their role as signaling molecules, but an excessive production is detrimental due to unwanted oxidation reactions that impact on the function of different types of biomolecules contained in mitochondria. Therefore, the maintenance of the redox balance in the IMS is essential for mitochondrial function. In this review, we will discuss the role that redox regulation plays in the maintenance of IMS homeostasis as well as how mitochondrial ROS generation may be a key regulatory factor for ETC biogenesis, especially for complex IV.

scholarly journals Insertion of plastidic β-barrel proteins into the outer envelopes of plastids involves an intermembrane space intermediate formed with Toc75-V/OEP80

2021 ◽  
Author(s):  
Lucia E Gross ◽  
Anna Klinger ◽  
Nicole Spies ◽  
Theresa Ernst ◽  
Nadine Flinner ◽  
...  
Keyword(s):  
Membrane Proteins ◽  
Protein Import ◽  
Membrane Insertion ◽  
Intermembrane Space ◽  
Envelope Membrane ◽  
Outer Envelope ◽  
Pea Proteins ◽  
Outer Envelope Membrane ◽  
Correct Topology ◽  
Shed Light

Abstract The insertion of organellar membrane proteins with the correct topology requires the following: First, the proteins must contain topogenic signals for translocation across and insertion into the membrane. Second, proteinaceous complexes in the cytoplasm, membrane, and lumen of organelles are required to drive this process. Many complexes required for the intracellular distribution of membrane proteins have been described, but the signals and components required for the insertion of plastidic β-barrel-type proteins into the outer membrane are largely unknown. The discovery of common principles is difficult, as only a few plastidic β-barrel proteins exist. Here, we provide evidence that the plastidic outer envelope β-barrel proteins OEP21, OEP24, and OEP37 from pea (Pisum sativum) and Arabidopsis thaliana contain information defining the topology of the protein. The information required for translocation of pea proteins across the outer envelope membrane is present within the six N-terminal β-strands. This process requires the action of TOC (translocon of the outer chloroplast membrane). After translocation into the intermembrane space, β-barrel proteins interact with TOC75-V, as exemplified by OEP37 and P39, and are integrated into the membrane. The membrane insertion of plastidic β-barrel proteins is affected by mutation of the last β-strand, suggesting that this strand contributes to the insertion signal. These findings shed light on the elements and complexes involved in plastidic β-barrel protein import.

scholarly journals The Mitochondrial Intermembrane Space Oxireductase Mia40 Funnels the Oxidative Folding Pathway of the CytochromecOxidase Assembly Protein Cox19

2014 ◽  
Vol 289 (14) ◽  
pp. 9852-9864 ◽  
Author(s):  
Hugo Fraga ◽  
Joan-Josep Bech-Serra ◽  
Francesc Canals ◽  
Gabriel Ortega ◽  
Oscar Millet ◽  
...  
Keyword(s):  
Folding Pathway ◽  
Intermembrane Space ◽  
Oxidative Folding ◽  
Mitochondrial Intermembrane Space
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