mitochondrial protein synthesis
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Dysfunction of mitochondria induced by ischemia is considered to be a key event triggering neuronal cell death after brain ischemia. Here we report the effect of ischemia-reperfusion on mitochondrial protein synthesis and activity of cytochrome c oxidase (EC 1.9.3.1, COX). By performing 4-vessel occlusion model of global brain ischemia, we have observed that 15 min of global ischemia led to the inhibition of COX subunit I (COXI) synthesis to 56 % of control. After 1, 3 and 24 h of reperfusion, COXI synthesis was inhibited to 46, 50 and 72 % of control, respectively. Depressed synthesis of COXI was not a result of either diminished transcription of COXI gene or increased proteolytic degradation of COXI, since both Northern hybridization and Western blotting did not show significant changes in COXI mRNA and protein level. Thus, ischemia-reperfusion affects directly mitochondrial translation machinery. In addition, ischemia in duration of 15 min and consequent 1, 3 and 24 h of reperfusion led to the inhibition of COX activity to 90.3, 80.3, 81.9 and 83.5 % of control, respectively. Based on our data, we suggest that inhibition of COX activity is rather caused by ischemia-induced modification of COX polypeptides than by inhibition of mitochondrial translation.
- MeSH
- časové faktory MeSH
- down regulace MeSH
- financování organizované MeSH
- genetická transkripce MeSH
- ischemie mozku enzymologie komplikace MeSH
- krysa rodu rattus MeSH
- messenger RNA metabolismus MeSH
- mitochondriální proteiny biosyntéza genetika MeSH
- mitochondrie enzymologie MeSH
- modely nemocí na zvířatech MeSH
- mozková kůra enzymologie MeSH
- posttranslační úpravy proteinů MeSH
- potkani Wistar MeSH
- regulace genové exprese enzymů MeSH
- reperfuzní poškození enzymologie etiologie MeSH
- respirační komplex IV biosyntéza genetika metabolismus MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- mužské pohlaví MeSH
- zvířata MeSH
Letm1 is a conserved protein in eukaryotes bearing energized mitochondria. Hemizygous deletion of its gene has been implicated in symptoms of the human disease Wolf-Hirschhorn syndrome. Studies almost exclusively performed in opisthokonts have attributed several roles to Letm1, including maintaining mitochondrial morphology, mediating either calcium or potassium/proton antiport, and facilitating mitochondrial translation. We address the ancestral function of Letm1 in the highly diverged protist and significant pathogen, Trypanosoma brucei. We demonstrate that Letm1 is involved in maintaining mitochondrial volume via potassium/proton exchange across the inner membrane. This role is essential in the vector-dwelling procyclic and mammal-infecting bloodstream stages as well as in Trypanosoma brucei evansi, a form of the latter stage lacking an organellar genome. In the pathogenic bloodstream stage, the mitochondrion consumes ATP to maintain an energized state, whereas that of T. brucei evansi also lacks a conventional proton-driven membrane potential. Thus, Letm1 performs its function in different physiological states, suggesting that ion homeostasis is among the few characterized essential pathways of the mitochondrion at this T. brucei life stage. Interestingly, Letm1 depletion in the procyclic stage can be complemented by exogenous expression of its human counterpart, highlighting the conservation of protein function between highly divergent species. Furthermore, although mitochondrial translation is affected upon Letm1 ablation, it is an indirect consequence of K(+) accumulation in the matrix.
- MeSH
- antibakteriální látky farmakologie MeSH
- draslík metabolismus MeSH
- fenotyp MeSH
- homeostáza MeSH
- kationty MeSH
- lidé MeSH
- membránový potenciál mitochondrií MeSH
- mitochondriální proteiny chemie metabolismus fyziologie MeSH
- mitochondrie metabolismus MeSH
- proteosyntéza MeSH
- protozoální proteiny chemie metabolismus fyziologie MeSH
- průtoková cytometrie metody MeSH
- RNA interference MeSH
- testy genetické komplementace MeSH
- Trypanosoma brucei brucei metabolismus MeSH
- umlčování genů MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The oxidative phosphorylation (OXPHOS) system localized in the inner mitochondrial membrane secures production of the majority of ATP in mammalian organisms. Individual OXPHOS complexes form supramolecular assemblies termed supercomplexes. The complexes are linked not only by their function but also by interdependency of individual complex biogenesis or maintenance. For instance, cytochrome c oxidase (cIV) or cytochrome bc1 complex (cIII) deficiencies affect the level of fully assembled NADH dehydrogenase (cI) in monomeric as well as supercomplex forms. It was hypothesized that cI is affected at the level of enzyme assembly as well as at the level of cI stability and maintenance. However, the true nature of interdependency between cI and cIV is not fully understood yet. We used a HEK293 cellular model where the COX4 subunit was completely knocked out, serving as an ideal system to study interdependency of cI and cIV, as early phases of cIV assembly process were disrupted. Total absence of cIV was accompanied by profound deficiency of cI, documented by decrease in the levels of cI subunits and significantly reduced amount of assembled cI. Supercomplexes assembled from cI, cIII, and cIV were missing in COX4I1 knock-out (KO) due to loss of cIV and decrease in cI amount. Pulse-chase metabolic labeling of mitochondrial DNA (mtDNA)-encoded proteins uncovered a decrease in the translation of cIV and cI subunits. Moreover, partial impairment of mitochondrial protein synthesis correlated with decreased content of mitochondrial ribosomal proteins. In addition, complexome profiling revealed accumulation of cI assembly intermediates, indicating that cI biogenesis, rather than stability, was affected. We propose that attenuation of mitochondrial protein synthesis caused by cIV deficiency represents one of the mechanisms, which may impair biogenesis of cI.
- MeSH
- glykolýza MeSH
- HEK293 buňky MeSH
- lidé MeSH
- mitochondriální nemoci metabolismus MeSH
- mitochondriální proteiny biosyntéza MeSH
- oxidativní fosforylace MeSH
- podjednotky proteinů metabolismus MeSH
- proteosyntéza * MeSH
- respirační komplex IV metabolismus MeSH
- spotřeba kyslíku MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
We have generated a high-confidence mitochondrial proteome (MitoTag) of the Trypanosoma brucei procyclic stage containing 1,239 proteins. For 337 of these, a mitochondrial localization had not been described before. We use the TrypTag dataset as a foundation and take advantage of the properties of the fluorescent protein tag that causes aberrant but fortuitous accumulation of tagged matrix and inner membrane proteins near the kinetoplast (mitochondrial DNA). Combined with transmembrane domain predictions, this characteristic allowed categorization of 1,053 proteins into mitochondrial sub-compartments, the detection of unique matrix-localized fucose and methionine synthesis, and the identification of new kinetoplast proteins, which showed kinetoplast-linked pyrimidine synthesis. Moreover, disruption of targeting signals by tagging allowed mapping of the mode of protein targeting to these sub-compartments, identifying a set of C-tail anchored outer mitochondrial membrane proteins and mitochondrial carriers likely employing multiple target peptides. This dataset represents a comprehensive, updated mapping of the mitochondrion.
- MeSH
- biologie MeSH
- mitochondriální proteiny metabolismus MeSH
- mitochondrie metabolismus MeSH
- paraziti * metabolismus MeSH
- protozoální proteiny metabolismus MeSH
- Trypanosoma brucei brucei * metabolismus MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
UNLABELLED: Mitochondrial chaperones have multiple functions that are essential for proper functioning of mitochondria. In the human-pathogenic protist Trypanosoma brucei, we demonstrate a novel function of the highly conserved machinery composed of mitochondrial heat shock proteins 70 and 40 (mtHsp70/mtHsp40) and the ATP exchange factor Mge1. The mitochondrial DNA of T. brucei, also known as kinetoplast DNA (kDNA), is represented by a single catenated network composed of thousands of minicircles and dozens of maxicircles packed into an electron-dense kDNA disk. The chaperones mtHsp70 and mtHsp40 and their cofactor Mge1 are uniformly distributed throughout the single mitochondrial network and are all essential for the parasite. Following RNA interference (RNAi)-mediated depletion of each of these proteins, the kDNA network shrinks and eventually disappears. Ultrastructural analysis of cells depleted for mtHsp70 or mtHsp40 revealed that the otherwise compact kDNA network becomes severely compromised, a consequence of decreased maxicircle and minicircle copy numbers. Moreover, we show that the replication of minicircles is impaired, although the lack of these proteins has a bigger impact on the less abundant maxicircles. We provide additional evidence that these chaperones are indispensable for the maintenance and replication of kDNA, in addition to their already known functions in Fe-S cluster synthesis and protein import. IMPORTANCE: Impairment or loss of mitochondrial DNA is associated with mitochondrial dysfunction and a wide range of neural, muscular, and other diseases. We present the first evidence showing that the entire mtHsp70/mtHsp40 machinery plays an important role in mitochondrial DNA replication and maintenance, a function likely retained from prokaryotes. These abundant, ubiquitous, and multifunctional chaperones share phenotypes with enzymes engaged in the initial stages of replication of the mitochondrial DNA in T. brucei.
- MeSH
- kinetoplastová DNA genetika metabolismus MeSH
- lidé MeSH
- mitochondriální DNA genetika metabolismus MeSH
- mitochondrie genetika metabolismus MeSH
- proteiny tepelného šoku HSP40 genetika metabolismus MeSH
- proteiny tepelného šoku HSP70 genetika metabolismus MeSH
- protozoální proteiny genetika metabolismus MeSH
- replikace DNA * MeSH
- Trypanosoma brucei brucei genetika metabolismus MeSH
- trypanozomóza africká parazitologie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, N.I.H., Extramural MeSH
Recent data suggest that frataxin plays a key role in eukaryote cellular iron metabolism, particularly in mitochondrial heme and iron-sulfur (FeS) cluster biosynthesis. We have now identified a frataxin homologue (T. vaginalis frataxin) from the human parasite Trichomonas vaginalis. Instead of mitochondria, this unicellular eukaryote possesses hydrogenosomes, peculiar organelles that produce hydrogen but nevertheless share common ancestry with mitochondria. T. vaginalis frataxin contains conserved residues implicated in iron binding, and in silico, it is predicted to form a typical alpha-beta sandwich motif. The short N-terminal extension of T. vaginalis frataxin resembles presequences that target proteins to hydrogenosomes, a prediction confirmed by the results of overexpression of T. vaginalis frataxin in T. vaginalis. When expressed in the mitochondria of a frataxin-deficient Saccharomyces cerevisiae strain, T. vaginalis frataxin partially restored defects in heme and FeS cluster biosynthesis. Although components of heme synthesis or heme-containing proteins have not been found in T. vaginalis to date, T. vaginalis frataxin was also shown to interact with S. cerevisiae ferrochelatase by using a Biacore assay. The discovery of conserved iron-metabolizing pathways in mitochondria and hydrogenosomes provides additional evidence not only of their common evolutionary history, but also of the fundamental importance of this pathway for eukaryotes.
- MeSH
- financování organizované MeSH
- genetická transkripce MeSH
- konzervovaná sekvence MeSH
- mitochondriální proteiny genetika metabolismus MeSH
- molekulární modely MeSH
- molekulární sekvence - údaje MeSH
- organely metabolismus MeSH
- proteiny vázající železo genetika metabolismus MeSH
- sekvence aminokyselin MeSH
- sekvenční seřazení MeSH
- Trichomonas vaginalis genetika metabolismus MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
Mitochondrial ribosomes evolved from prokaryotic ribosomes, with which they therefore share more common features than with their counterparts in the cytosol. Yet, mitochondrial ribosomes are highly diverse in structure and composition, having undergone considerable changes, including reduction of their RNA component and varying degree of acquisition of novel proteins in various phylogenetic lineages. Here, we present functional analysis of three putative mitochondrial ribosome-associated proteins (RSM22, mtYsxC and PNKD-like) in Trypanosoma brucei, originally identified by database mining. While in other systems the homologs of RSM22 are known as components of mitochondrial ribosomes, YsxC was linked with ribosomes only in bacteria. The PNKD-like protein shows similarity to a human protein, the defects of which cause PNKD (paroxysmal non-kinesigenic dyskinesia). Here we show that all three proteins are important for the growth of T. brucei. They play an important function in mitochondrial translation, as their ablation by RNAi rapidly and severely affected the de novo synthesis of mitochondrial proteins. Moreover, following the RNAi-mediated depletion of RSM22, structure of the small subunit of mitochondrial ribosome becomes severely compromised, suggesting a role of RSM22 in ribosomal assembly and/or stability.
- MeSH
- mitochondriální proteiny genetika metabolismus MeSH
- proteosyntéza * MeSH
- protozoální proteiny genetika metabolismus MeSH
- RNA interference MeSH
- sekvenční homologie aminokyselin MeSH
- Trypanosoma brucei brucei genetika růst a vývoj MeSH
- umlčování genů MeSH
- výpočetní biologie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, N.I.H., Extramural MeSH
Genes encoding the KDM5 family of transcriptional regulators are disrupted in individuals with intellectual disability (ID). To understand the link between KDM5 and ID, we characterized five Drosophila strains harboring missense alleles analogous to those observed in patients. These alleles disrupted neuroanatomical development, cognition and other behaviors, and displayed a transcriptional signature characterized by the downregulation of many ribosomal protein genes. A similar transcriptional profile was observed in KDM5C knockout iPSC-induced human glutamatergic neurons, suggesting an evolutionarily conserved role for KDM5 proteins in regulating this class of gene. In Drosophila, reducing KDM5 changed neuronal ribosome composition, lowered the translation efficiency of mRNAs required for mitochondrial function, and altered mitochondrial metabolism. These data highlight the cellular consequences of altered KDM5-regulated transcriptional programs that could contribute to cognitive and behavioral phenotypes. Moreover, they suggest that KDM5 may be part of a broader network of proteins that influence cognition by regulating protein synthesis.
- MeSH
- aktivace transkripce MeSH
- Drosophila melanogaster genetika metabolismus MeSH
- Drosophila genetika metabolismus MeSH
- histondemethylasy metabolismus genetika MeSH
- lidé MeSH
- mentální retardace genetika metabolismus MeSH
- mitochondrie metabolismus genetika MeSH
- neurony * metabolismus MeSH
- proteiny Drosophily * genetika metabolismus MeSH
- proteosyntéza MeSH
- ribozomální proteiny * genetika metabolismus MeSH
- ribozomy metabolismus genetika MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
Mitochondria are organelles present in most eukaryotic cells, where they play major and multifaceted roles. The classical notion of the main mitochondrial function as the powerhouse of the cell per se has been complemented by recent discoveries pointing to mitochondria as organelles affecting a number of other auxiliary processes. They go beyond the classical energy provision via acting as a relay point of many catabolic and anabolic processes, to signaling pathways critically affecting cell growth by their implication in de novo pyrimidine synthesis. These additional roles further underscore the importance of mitochondrial homeostasis in various tissues, where its deregulation promotes a number of pathologies. While it has long been known that mitochondria can move within a cell to sites where they are needed, recent research has uncovered that mitochondria can also move between cells. While this intriguing field of research is only emerging, it is clear that mobilization of mitochondria requires a complex apparatus that critically involves mitochondrial proteins of the Miro family, whose role goes beyond the mitochondrial transfer, as will be covered in this review.
- MeSH
- aktivní transport fyziologie MeSH
- lidé MeSH
- mitochondriální proteiny genetika metabolismus MeSH
- mitochondrie genetika metabolismus MeSH
- pyrimidiny biosyntéza MeSH
- rho proteiny vázající GTP genetika metabolismus MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- audiovizuální média MeSH
- časopisecké články MeSH
- práce podpořená grantem MeSH
- přehledy MeSH
