Mitochondrial oxidative phosphorylation (OXPHOS) generates ATP, but OXPHOS also supports biosynthesis during proliferation. In contrast, the role of OXPHOS during quiescence, beyond ATP production, is not well understood. Using mouse models of inducible OXPHOS deficiency in all cell types or specifically in the vascular endothelium that negligibly relies on OXPHOS-derived ATP, we show that selectively during quiescence OXPHOS provides oxidative stress resistance by supporting macroautophagy/autophagy. Mechanistically, OXPHOS constitutively generates low levels of endogenous ROS that induce autophagy via attenuation of ATG4B activity, which provides protection from ROS insult. Physiologically, the OXPHOS-autophagy system (i) protects healthy tissue from toxicity of ROS-based anticancer therapy, and (ii) provides ROS resistance in the endothelium, ameliorating systemic LPS-induced inflammation as well as inflammatory bowel disease. Hence, cells acquired mitochondria during evolution to profit from oxidative metabolism, but also built in an autophagy-based ROS-induced protective mechanism to guard against oxidative stress associated with OXPHOS function during quiescence.Abbreviations: AMPK: AMP-activated protein kinase; AOX: alternative oxidase; Baf A: bafilomycin A1; CI, respiratory complexes I; DCF-DA: 2',7'-dichlordihydrofluorescein diacetate; DHE: dihydroethidium; DSS: dextran sodium sulfate; ΔΨmi: mitochondrial inner membrane potential; EdU: 5-ethynyl-2'-deoxyuridine; ETC: electron transport chain; FA: formaldehyde; HUVEC; human umbilical cord endothelial cells; IBD: inflammatory bowel disease; LC3B: microtubule associated protein 1 light chain 3 beta; LPS: lipopolysaccharide; MEFs: mouse embryonic fibroblasts; MTORC1: mechanistic target of rapamycin kinase complex 1; mtDNA: mitochondrial DNA; NAC: N-acetyl cysteine; OXPHOS: oxidative phosphorylation; PCs: proliferating cells; PE: phosphatidylethanolamine; PEITC: phenethyl isothiocyanate; QCs: quiescent cells; ROS: reactive oxygen species; PLA2: phospholipase A2, WB: western blot.

• Klíčová slova
• ATG4B, biosynthesis, cell death, electron transport chain, endothelial cells, mitochondria, oxidative phosphorylation, oxidative stress, reactive oxygen species,
• MeSH
• adenosintrifosfát metabolismus   MeSH
• autofagie * MeSH
• cystein metabolismus   MeSH
• dextrany metabolismus   MeSH
• dýchání MeSH
• endoteliální buňky metabolismus   MeSH
• fibroblasty metabolismus   MeSH
• formaldehyd metabolismus   MeSH
• fosfatidylethanolaminy metabolismus   MeSH
• idiopatické střevní záněty * metabolismus   MeSH
• isothiokyanatany MeSH
• lidé MeSH
• lipopolysacharidy metabolismus   MeSH
• mechanistické cílové místo rapamycinového komplexu 1 metabolismus   MeSH
• mitochondriální DNA metabolismus   MeSH
• mitochondrie metabolismus   MeSH
• myši MeSH
• proteinkinasy aktivované AMP metabolismus   MeSH
• proteiny asociované s mikrotubuly metabolismus   MeSH
• reaktivní formy kyslíku metabolismus   MeSH
• sirolimus MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• adenosintrifosfát MeSH
• cystein MeSH
• dextrany MeSH
• formaldehyd MeSH
• fosfatidylethanolaminy MeSH
• isothiokyanatany MeSH
• lipopolysacharidy MeSH
• mechanistické cílové místo rapamycinového komplexu 1 MeSH
• mitochondriální DNA MeSH
• phenethyl isothiocyanate MeSH Prohlížeč
• proteinkinasy aktivované AMP MeSH
• proteiny asociované s mikrotubuly MeSH
• reaktivní formy kyslíku MeSH
• sirolimus MeSH

Mitochondrial ATP synthase is a reversible nanomotor synthesizing or hydrolyzing ATP depending on the potential across the membrane in which it is embedded. In the unicellular parasite Trypanosoma brucei, the direction of the complex depends on the life cycle stage of this digenetic parasite: in the midgut of the tsetse fly vector (procyclic form), the FoF1-ATP synthase generates ATP by oxidative phosphorylation, whereas in the mammalian bloodstream form, this complex hydrolyzes ATP and maintains mitochondrial membrane potential (ΔΨm). The trypanosome FoF1-ATP synthase contains numerous lineage-specific subunits whose roles remain unknown. Here, we seek to elucidate the function of the lineage-specific protein Tb1, the largest membrane-bound subunit. In procyclic form cells, Tb1 silencing resulted in a decrease of FoF1-ATP synthase monomers and dimers, rerouting of mitochondrial electron transfer to the alternative oxidase, reduced growth rate and cellular ATP levels, and elevated ΔΨm and total cellular reactive oxygen species levels. In bloodstream form parasites, RNAi silencing of Tb1 by ∼90% resulted in decreased FoF1-ATPase monomers and dimers, but it had no apparent effect on growth. The same findings were obtained by silencing of the oligomycin sensitivity-conferring protein, a conserved subunit in T. brucei FoF1-ATP synthase. However, as expected, nearly complete Tb1 or oligomycin sensitivity-conferring protein suppression was lethal because of the inability to sustain ΔΨm. The diminishment of FoF1-ATPase complexes was further accompanied by a decreased ADP/ATP ratio and reduced oxygen consumption via the alternative oxidase. Our data illuminate the often diametrically opposed bioenergetic consequences of FoF1-ATP synthase loss in insect versus mammalian forms of the parasite.

• Klíčová slova
• ATP synthase, ATPase, Trypanosoma brucei, alternative oxidase, bioenergetics, electron transport, mitochondria, mitochondrial membrane potential, oxidative phosphorylation, respiration,
• MeSH
• adenosintrifosfát genetika   metabolismus   MeSH
• buněčný cyklus * MeSH
• energetický metabolismus * MeSH
• membránový potenciál mitochondrií MeSH
• mitochondrie genetika   metabolismus   MeSH
• protonové ATPasy nedostatek   metabolismus   MeSH
• protozoální proteiny genetika   metabolismus   MeSH
• Trypanosoma brucei brucei genetika   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• adenosintrifosfát MeSH
• protonové ATPasy MeSH
• protozoální proteiny MeSH

Tumor cells without mitochondrial (mt) DNA (ρ0 cells) are auxotrophic for uridine, and their growth is supported by pyruvate. While ATP synthesis in ρ0 cells relies on glycolysis, they fail to form tumors unless they acquire mitochondria from stromal cells. Mitochondrial acquisition restores respiration that is essential for de novo pyrimidine biosynthesis and for mitochondrial ATP production. The physiological processes that underpin intercellular mitochondrial transfer to tumor cells lacking mtDNA and the metabolic remodeling and restored tumorigenic properties of cells that acquire mitochondria are not well understood. Here, we investigated the changes in mitochondrial and nuclear gene expression that accompany mtDNA deletion and acquisition in metastatic murine 4T1 breast cancer cells. Loss of mitochondrial gene expression in 4T1ρ0 cells was restored in cells recovered from subcutaneous tumors that grew from 4T1ρ0 cells following acquisition of mtDNA from host cells. In contrast, the expression of most nuclear genes that encode respiratory complex subunits and mitochondrial ribosomal subunits was not greatly affected by loss of mtDNA, indicating ineffective mitochondria-to-nucleus communication systems for these nuclear genes. Further, analysis of nuclear genes whose expression was compromised in 4T1ρ0 cells showed that immune- and stress-related genes were the most highly differentially expressed, representing over 70% of those with greater than 16-fold higher expression in 4T1 compared with 4T1ρ0 cells. The monocyte recruiting chemokine, Ccl2, and Psmb8, a subunit of the immunoproteasome that generates MHCI-binding peptides, were the most highly differentially expressed. Early monocyte/macrophage recruitment into the tumor mass was compromised in 4T1ρ0 cells but recovered before mtDNA could be detected. Taken together, our results show that mitochondrial acquisition by tumor cells without mtDNA results in bioenergetic remodeling and re-expression of genes involved in immune function and stress adaptation.

• Klíčová slova
• 4T1 model, breast cancer, gene expression, mitochondrial DNA, tumor macrophages,
• Publikační typ
• časopisecké články MeSH

Mitochondrial dysfunctions belong amongst the most common metabolic diseases but the signalling networks that lead to the manifestation of a disease phenotype are often not well understood. We identified the subunits of respiratory complex I, III and IV as mediators of major signalling changes during Drosophila wing disc development. Their downregulation in larval wing disc leads to robust stimulation of TOR activity, which in turn orchestrates a complex downstream signalling network. Specifically, after downregulation of the complex I subunit ND-49 (mammalian NDUFS2), TOR activates JNK to induce cell death and ROS production essential for the stimulation of compensatory apoptosis-induced proliferation within the tissue. Additionally, TOR upregulates Notch and JAK/STAT signalling and it directs glycolytic switch of the target tissue. Our results highlight the central role of TOR signalling in mediating the complex response to mitochondrial respiratory dysfunction and they provide a rationale why the disease symptoms associated with respiratory dysfunctions are often alleviated by mTOR inhibitors.

• MeSH
• down regulace MeSH
• Drosophila MeSH
• Janus kinasy metabolismus   MeSH
• křídla zvířecí růst a vývoj   metabolismus   MeSH
• proteiny Drosophily genetika   metabolismus   MeSH
• reaktivní formy kyslíku metabolismus   MeSH
• receptory Notch metabolismus   MeSH
• respirační komplex I genetika   metabolismus   MeSH
• signální transdukce * MeSH
• transkripční faktory STAT metabolismus   MeSH
• tyrosinkinasové receptory metabolismus   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• Janus kinasy MeSH
• N protein, Drosophila MeSH Prohlížeč
• proteiny Drosophily MeSH
• reaktivní formy kyslíku MeSH
• receptory Notch MeSH
• respirační komplex I MeSH
• tor protein, Drosophila MeSH Prohlížeč
• transkripční faktory STAT MeSH
• tyrosinkinasové receptory MeSH

In the infectious stage of Trypanosoma brucei, an important parasite of humans and livestock, the mitochondrial (mt) membrane potential (Δψm) is uniquely maintained by the ATP hydrolytic activity and subsequent proton pumping of the essential FoF1-ATPase. Intriguingly, this multiprotein complex contains several trypanosome-specific subunits of unknown function. Here, we demonstrate that one of the largest novel subunits, ATPaseTb2, is membrane-bound and localizes with monomeric and multimeric assemblies of the FoF1-ATPase. Moreover, RNAi silencing of ATPaseTb2 quickly leads to a significant decrease of the Δψm that manifests as a decreased growth phenotype, indicating that the FoF1-ATPase is impaired. To further explore the function of this protein, we employed a trypanosoma strain that lacks mtDNA (dyskinetoplastic, Dk) and thus subunit a, an essential component of the proton pore in the membrane Fo-moiety. These Dk cells generate the Δψm by combining the hydrolytic activity of the matrix-facing F1-ATPase and the electrogenic exchange of ATP4- for ADP3- by the ATP/ADP carrier (AAC). Surprisingly, in addition to the expected presence of F1-ATPase, the monomeric and multimeric FoF1-ATPase complexes were identified. In fact, the immunoprecipitation of a F1-ATPase subunit demonstrated that ATPaseTb2 was a component of these complexes. Furthermore, RNAi studies established that the membrane-bound ATPaseTb2 subunit is essential for maintaining normal growth and the Δψm of Dk cells. Thus, even in the absence of subunit a, a portion of the FoF1-ATPase is assembled in Dk cells.

• MeSH
• geneticky modifikované organismy MeSH
• kultivované buňky MeSH
• lidé MeSH
• membránové proteiny fyziologie   MeSH
• mitochondriální DNA genetika   MeSH
• mitochondrie genetika   metabolismus   MeSH
• podjednotky proteinů fyziologie   MeSH
• protonové ATPasy fyziologie   MeSH
• skot MeSH
• Trypanosoma brucei brucei * genetika   metabolismus   patogenita   ultrastruktura   MeSH
• trypanozomóza africká krev   parazitologie   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• skot MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• membránové proteiny MeSH
• mitochondriální DNA MeSH
• podjednotky proteinů MeSH
• protonové ATPasy MeSH