The basal proton conductance of mitochondria depends on adenine nucleotide translocase content.
Ontology highlight
ABSTRACT:
SUBMITTER: Brand MD
PROVIDER: S-EPMC1316271 | biostudies-other | 2005 Dec
REPOSITORIES: biostudies-other
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Project description:Reperfusion is the only feasible therapy following myocardial infarction, but reperfusion has been shown to damage mitochondrial function and disrupt energy production in the heart. Adenine nucleotide translocase 1 (ANT1) facilitates the transfer of ADP/ATP across the inner mitochondrial membrane; therefore, we tested whether ANT1 exerts protective effects on mitochondrial function during ischemia/reperfusion (I/R). The hearts of wild-type (WT) and transgenic ANT1-overexpressing (ANT1-TG) rats were exposed to I/R injury using the standard Langendorff technique, after which mitochondrial function, hemodynamic parameters, infarct size, and components of the contractile apparatus were determined. ANT1-TG hearts expressed higher ANT protein levels, with reduced levels of oxidative 4-hydroxynonenal ANT modifications following I/R. ANT1-TG mitochondria isolated from I/R hearts displayed stable calcium retention capacity (CRC) and improved membrane potential stability compared with WT mitochondria. Mitochondria isolated from ANT1-TG hearts experienced less restricted oxygen consumption than WT mitochondria after I/R. Left ventricular diastolic pressure (Pdia) decreased in ANT1-TG hearts compared with WT hearts following I/R. Preserved diastolic function was accompanied by a decrease in the phospho-lamban (PLB)/sarcoplasmic reticulum calcium ATPase (SERCA2a) ratio in ANT1-TG hearts compared with that in WT hearts. In addition, the phosphorylated (P)-PLB/PLB ratio increased in ANT1-TG hearts after I/R but not in WT hearts, which indicated more effective calcium uptake into the sarcoplasmic reticulum in ANT1-TG hearts. In conclusion, ANT1-TG rat hearts coped more efficiently with I/R than WT rat hearts, which was reflected by preserved mitochondrial energy balance, diastolic function, and calcium dynamics after reperfusion.
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Project description:Electrophilic nitrated lipids (nitroalkenes) are emerging as an important class of protective cardiovascular signaling molecules. Although species such as nitro-linoleate (LNO(2)) and nitro-oleate can confer acute protection against cardiac ischemic injury, their mechanism of action is unclear. Mild uncoupling of mitochondria is known to be cardioprotective, and adenine nucleotide translocase 1 (ANT1) is a key mediator of mitochondrial uncoupling. ANT1 also contains redox-sensitive cysteines that may be targets for modification by nitroalkenes. Therefore, in this study we tested the hypothesis that nitroalkenes directly modify ANT1 and that nitroalkene-mediated cardioprotection requires ANT1. Using biotin-tagged LNO(2) infused into intact perfused hearts, we obtained mass spectrometric (MALDI-TOF-TOF) evidence for direct modification (nitroalkylation) of ANT1 on cysteine 57. Furthermore, in a cell model of ischemia-reperfusion injury, siRNA knockdown of ANT1 inhibited the cardioprotective effect of LNO(2). Although the molecular mechanism linking ANT1-Cys(57) nitroalkylation and uncoupling is not yet known, these data suggest that ANT1-mediated uncoupling may be a mechanism for nitroalkene-induced cardioprotection.
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Project description:Phosphorylation of adenine nucleotide translocator 1 (ANT1) at residue Y194, which is part of the aromatic ladder located within the lumen of the carrier, critically regulates mitochondrial metabolism. Recent data support the concept that members of the Src family of nonreceptor tyrosine kinases are constitutively present in mitochondria and key to regulation of mitochondrial function. Herein, we demonstrate that site mutations of ANT1 (Y190-->F190, Y194-->F194) mimicking dephosphorylation of the aromatic ladder resulted in loss of oxidative growth and ADP/ATP exchange activity in respiration-incompetent yeast expressing mutant chimeric yN-hANT1. ANT1 is phosphorylated at Y194 by the Src family kinase members Src and Lck, and increased phosphorylation is tightly linked to reduced cell injury in preconditioned protected vs. unprotected cardiac mitochondria. Molecular dynamics simulations find the overall structure of the phosphorylated ANT1 stable, but with an increased steric flexibility in the region of the aromatic ladder, matrix loop m2, and four helix-linking regions. Combined with an analysis of the putative cytosolic salt bridge network, we reason that the effect of phosphorylation on transport is likely due to an accelerated transition between the main two conformational states (c<-->m) of the carrier during the transport cycle. Since "aromatic signatures" are typical for other mitochondrial carrier proteins with important biological functions, our results may be more general and applicable to these carriers.
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Project description:The protein adenine nucleotide translocase (ANT) is localized in the mitochondrial inner membrane and plays an essential role in transporting ADP into the mitochondrial matrix and ATP out from the matrix for cell utilization. In mammals there are four paralogous ANT genes, of which ANT4 is exclusively expressed in meiotic germ cells. Since ANT4 has been shown essential for spermatogenesis and male fertility in mice, inhibition of ANT4 appears to be a reasonable target for male contraceptive development. Further, in contrast to ANT1, ANT2 and ANT3 that are highly homologous to each other, ANT4 has a distinguishable amino acid sequence, which serves as a basis to develop a selective ANT4 inhibitor. In this study, we aimed to identify candidate compounds that can selectively inhibit ANT4 activity over the other ANTs. We used a structure-based method in which ANT4 was modeled then utilized as the basis for selection of compounds that interact with sites unique to ANT4. A large chemical library (>100,000 small molecules) was screened by molecular docking and effects of these compounds on ADP/ATP exchange through ANT4 were examined using yeast mitochondria expressing human ANT4. Through this, we identified one particular candidate compound, [2,2'-methanediylbis(4-nitrophenol)], which inhibits ANT4 activity with a lower IC50 than the other ANTs (5.8 μM, 4.1 μM, 5.1 μM and 1.4 μM for ANT1, 2, 3 and 4, respectively). This newly identified active lead compound and its chemical structure are expected to provide new opportunities to optimize selective ANT4 inhibitors for contraceptive purposes.
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Project description:The adenine nucleotide translocase (ANT) mediates the exchange of ADP and ATP across the inner mitochondrial membrane. The human genome encodes multiple ANT isoforms that are expressed in a tissue-specific manner. Recently a novel germ cell-specific member of the ANT family, ANT4 (SLC25A31) was identified. Although it is known that targeted depletion of ANT4 in mice resulted in male infertility, the functional biochemical differences between ANT4 and other somatic ANT isoforms remain undetermined. To gain insight into ANT4, we expressed human ANT4 (hANT4) in yeast mitochondria. Unlike the somatic ANT proteins, expression of hANT4 failed to complement an AAC-deficient yeast strain for growth on media requiring mitochondrial respiration. Moreover, overexpression of hANT4 from a multi-copy plasmid interfered with optimal yeast growth. However, mutation of specific amino acids of hANT4 improved yeast mitochondrial expression and supported growth of the AAC-deficient yeast on non-fermentable carbon sources. The mutations affected amino acids predicted to interact with phospholipids, suggesting the importance of lipid interactions for function of this protein. Each mutant hANT4 and the somatic hANTs exhibited similar ADP/ATP exchange kinetics. These data define common and distinct biochemical characteristics of ANT4 in comparison to ANT1, 2 and 3 providing a basis for study of its unique adaptation to germ cells.
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Project description:Adenine nucleotide translocase 1 (ANT1) transfers ATP and ADP over the mitochondrial inner membrane and thus supplies the cell with energy. This study analyzed the role of ANT1 in the immune response of ischemic heart tissue. Ischemic ANT1 overexpressing hearts experienced a shift toward an anti-inflammatory immune response. The shift was characterized by low interleukin (IL)-1β expression and M1 macrophage infiltration, whereas M2 macrophage infiltration and levels of IL-10, IL-4, and transforming growth factor (TGFβ) were increased. The modulated immune response correlated with high mitochondrial integrity, reduced oxidative stress, low left ventricular end-diastolic heart pressure, and a high survival rate. Isolated ANT1-transgenic (ANT1-TG) cardiomyocytes expressed low levels of pro-inflammatory cytokines such as IL-1α, tumor necrosis factor α, and TGFβ. However, they showed increased expression and cellular release of anti-inflammatory immunomodulators such as vascular endothelial growth factor. The secretome from ANT1-TG cardiomyocytes initiated stress resistance when applied to ischemic wild-type cardiomyocytes and endothelial cells. It additionally prevented macrophages from expressing pro-inflammatory cytokines. Additionally, ANT1 expression correlated with genes that are related to cytokine and growth factor pathways in hearts of patients with ischemic cardiomyopathy. In conclusion, ANT1-TG cardiomyocytes secrete soluble factors that influence ischemic cardiac cells and initiate an anti-inflammatory immune response in ischemic hearts.
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Project description:Airway hydration and ciliary function are critical to airway homeostasis and dysregulated in chronic obstructive pulmonary disease (COPD), which is impacted by cigarette smoking and has no therapeutic options. We utilized a high-copy cDNA library genetic selection approach in the amoeba Dictyostelium discoideum to identify genetic protectors to cigarette smoke. Members of the mitochondrial ADP/ATP transporter family adenine nucleotide translocase (ANT) are protective against cigarette smoke in Dictyostelium and human bronchial epithelial cells. Gene expression of ANT2 is reduced in lung tissue from COPD patients and in a mouse smoking model, and overexpression of ANT1 and ANT2 resulted in enhanced oxidative respiration and ATP flux. In addition to the presence of ANT proteins in the mitochondria, they reside at the plasma membrane in airway epithelial cells and regulate airway homeostasis. ANT2 overexpression stimulates airway surface hydration by ATP and maintains ciliary beating after exposure to cigarette smoke, both of which are key functions of the airway. Our study highlights a potential for upregulation of ANT proteins and/or of their agonists in the protection from dysfunctional mitochondrial metabolism, airway hydration and ciliary motility in COPD.This article has an associated First Person interview with the first author of the paper.
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Project description:Haem is a prosthetic group for haem proteins, which play an essential role in oxygen transport, respiration, signal transduction, and detoxification. In haem biosynthesis, the haem precursor protoporphyrin IX (PP IX) must be accumulated into the mitochondrial matrix across the inner membrane, but its mechanism is largely unclear. Here we show that adenine nucleotide translocator (ANT), the inner membrane transporter, contributes to haem biosynthesis by facilitating mitochondrial accumulation of its precursors. We identified that haem and PP IX specifically bind to ANT. Mitochondrial uptake of PP IX was inhibited by ADP, a known substrate of ANT. Conversely, ADP uptake into mitochondria was competitively inhibited by haem and its precursors, suggesting that haem-related porphyrins are accumulated into mitochondria via ANT. Furthermore, disruption of the ANT genes in yeast resulted in a reduction of haem biosynthesis by blocking the translocation of haem precursors into the matrix. Our results represent a new model that ANT plays a crucial role in haem biosynthesis by facilitating accumulation of its precursors into the mitochondrial matrix.
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Project description:2,4-Dinitrophenol (DNP) is a classic uncoupler of oxidative phosphorylation in mitochondria which is still used in "diet pills", despite its high toxicity and lack of antidotes. DNP increases the proton current through pure lipid membranes, similar to other chemical uncouplers. However, the molecular mechanism of its action in the mitochondria is far from being understood. The sensitivity of DNP's uncoupling action in mitochondria to carboxyatractyloside, a specific inhibitor of adenine nucleotide translocase (ANT), suggests the involvement of ANT and probably other mitochondrial proton-transporting proteins in the DNP's protonophoric activity. To test this hypothesis, we investigated the contribution of recombinant ANT1 and the uncoupling proteins UCP1-UCP3 to DNP-mediated proton leakage using the well-defined model of planar bilayer lipid membranes. All four proteins significantly enhanced the protonophoric effect of DNP. Notably, only long-chain free fatty acids were previously shown to be co-factors of UCPs and ANT1. Using site-directed mutagenesis and molecular dynamics simulations, we showed that arginine 79 of ANT1 is crucial for the DNP-mediated increase of membrane conductance, implying that this amino acid participates in DNP binding to ANT1.
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Project description:Adenine nucleotide translocase (ANT) is a nuclear-coded mitochondrial protein that exchanges ATP for ADP across the mitochondrial inner membrane. Most organisms possess several ANT paralogues, and functional differences among these paralogues remain largely unknown. In the present study, we identified ANT paralogue genes in hemipteran species: the stink bug, bean bug, pea aphid, and Japanese mealybug. The ANT paralogues of the stink bug, Plautia stali, are encoded by two genes, PsANTI1 and PsANTI2. PsANTI1 was constantly expressed at all developmental stages and in all tissues analyzed. In contrast, the expression levels of PsANTI2 were undetectable in first instar nymphs and adult antennae. Gene silencing of each paralogue in P. stali revealed that PsANTI1 plays an important role in homeostasis, whereas the depletion of PsANTI2 failed to result in lethality. Thus, we concluded that PsANTI1 is a good target gene for developing novel pesticides.
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