The adenine nucleotide translocator in foetal, suckling and adult rat liver mitochondria

The adenine nucleotide content of rat liver mitochondria was shown to increase significantly after birth. On the other hand, it was found that the ligand-binding properties of the adenine nucleotide translocator were essentially the same in foetal, suckling and adult rat liver mitochondria. These results are compatible with the proposal that the accumulation of adenine nucleotides which occurs during mitochondrial biogenesis and maturation is effected by a pathway different from the adenine nucleotide translocator.     

Perinatal changes in adenine nucleotide content of developing rat kidney

Adenine nucleotides have been measured in fetal and newborn kidneys of rat using the luciferine-luciferase method. In fetuses, between days 18 and 21 of gestation there is a drop of the relative amount of ATP in the renal nucleotide pool. Consequently, the kidneys of 21 days-old fetuses have lowered ATP/ADP ratio (3.6) and energy charge (0.80) compared with values found on day 18 (6.9 and 0.91, respectively); this relative energy deficit is heightened in progesterone induced postmaturity. One hour after delivery whether the gestational stage is 21, 22 or 23 days, there is a rise in ATP and a decrease in AMP content which restore a high energy level in kidney of the newborn and a 30% increase in the total adenine nucleotide pool.     

低压缺氧对大鼠脑线粒体腺苷酸转运体特性的影响

本文探讨低压缺氧对大鼠脑线粒体内膜腺苷酸转运体（adenine nucleotide translocator,ANT）转运特性的影响。实验将雄性Wistar大鼠随机分为常氧对照组和缺氧组,后者分别连续暴露于模拟5000m高原1、5、15、30d（23h／d）。分别于平原和模拟4000m高原断头处死动物,分离脑线粒体,用抑制剂终止法测定线粒体对。H-ADP的转运效率,抑制剂滴定法测定ANT密度,HPLC测定线粒体内腺苷酸含量。结果显示：缺氧后ANT转运活性均明显低于常氧组,缺氧不同天数线粒体内膜ANT分布密度无显著改变,线粒体内（ATP＋ADP）含量下降与转运活性变化一致。以上观察结果表明,低压缺氧暴露可显著抑制ANT转运活性,降低能量产生和利用的周转率,但不改变ANT密度,提示ANT活性改变是低压缺氧时细胞能量代谢障碍的重要机制。     

Characterization of pyrophosphate exchange by the reconstituted adenine nucleotide translocator from mitochondria

The transport of inorganic pyrophosphate (PPi) by the adenine nucleotide translocator from beef heart mitochondria was studied in a reconstituted system. The transport of PPi is dependent on appropriate transmembrane substrates. The activity of PPi exchange is about one tenth as compared to the ADP/ATP exchange, whereas the transport affinity for PPi is very low (2-5 mM). The adenine nucleotide carrier catalyzes a strict counterexchange of PPi and nucleotides with an exchange stoichiometry close to 1. The inhibitor specificity of PPi exchange is comparable to that of ADP/ATP exchange.     

Participation of the adenine nucleotide translocator in the regulation of pyruvate oxidation in heart mitochondria

A regulatory role of adenine nucleotide translocator (ANT) was determined by titration of mitochondrial respiration (state 3) with carboxyatractyloside. It was shown that ANT regulates pyruvate oxidation: the control strength is more pronounced after depletion of endogenous substrates or after the increase in extramitochondrial ATP/ADP. The rate of succinate oxidation is controlled mainly by succinate dehydrogenase, while ANT does not participate in its regulation.     

The adenine nucleotide translocator in apoptosis

Alteration of mitochondrial membrane permeability is a central mechanism leading invariably to cell death, which results, at least in part, from the opening of the permeability transition pore complex (PTPC). Indeed, extended PTPC opening is sufficient to trigger an increase in mitochondrial membrane permeability and apoptosis. Among the various PTPC components, the adenine nucleotide translocator (ANT) appears to act as a bi-functional protein which, on the one hand, contributes to a crucial step of aerobic energy metabolism, the ADP/ATP translocation, and on the other hand, can be converted into a pro-apoptotic pore under the control of onco- and anti-oncoproteins from the Bax/Bcl-2 family. In this review, we will discuss recent advances in the cooperation between ANT and Bax/Bcl-2 family members, the multiplicity of agents affecting ANT pore function and the putative role of ANT isoforms in apoptosis control.     

The role of adenine nucleotide translocator in the regulation of oxidative phosphorylation in heart mitochondria

The regulatory role of adenine nucleotide translocase in oxidative phosphorylation was determined by titration of respiration of isolated rabbit heart mitochondria with carboxyatractyloside in the creatine phosphokinase ADP-regenerating system, which is not rate-limiting. It was found that the respiration rate is not controlled by adenine nucleotide translocase in states 3 and 4. Within the physiological region of respiration (30-70% of the maximal rate), the control coefficient for ADP/ATP translocase is 0.62-0.75. Thus, translocase plays a key role in the regulation of oxidative phosphorylation.     

The contribution of adenine nucleotide loss to ischemia-induced impairment of rat kidney cortex mitochondria.

Adenine nucleotides and respiration were assayed with rat kidney mitochondria depleted of adenine nucleotides by pyrophosphate treatment and by normothermic ischemia, respectively, with the aim of identifying net uptake of ATP as well as elucidating the contribution of adenine nucleotide loss to the ischemic impairment of oxidative phosphorylation. Treatment of rat kidney mitochondria with pyrophosphate caused a loss of adenine nucleotides as well as a decrease of state 3 respiration. After incubation of pyrophosphate-treated mitochondria with ATP, Mg2+ and phosphate, the content of adenine nucleotides increased. We propose that kidney mitochondria possess a mechanism for net uptake of ATP. Restoration of a normal content of matrix adenine nucleotides was related to full recovery of the rate of state 3 respiration. A hyperbolic relationship between the matrix content of adenine nucleotides and the rate of state 3 respiration was observed. Mitochondria isolated from kidneys exposed to normothermic ischemia were characterized by a decrease in the content of adenine nucleotides as well as in state 3 respiration. Incubation of ischemic mitochondria with ATP, Mg2+ and phosphate restored the content of adenine nucleotides to values measured in freshly-isolated mitochondria. State 3 respiration of ischemic mitochondria reloaded with ATP recovered only partially. The rate of state 3 respiration increased by ATP-reloading approached that of uncoupler-stimulated respiration measured with ischemic mitochondria. These findings suggest that the decrease of matrix adenine nucleotides contributes to the impairment of ischemic mitochondria as well as underlining the occurrence of additional molecular changes of respiratory chain limiting the oxidative phosphorylation.     

Metabolite transport in rat kidney mitochondria: ornithine/phosphate translocator

Ornithine uptake by rat kidney mitochondria is here first shown by monitoring the reduction of the intramitochondrial pyridine nucleotides which occurs as a result of metabolism of imported ornithine via ornithine aminotransferase and 1-pyrroline-carboxylate dehydrogenase. Ornithine uptake shows saturation features (Km and Vmax values, measured at 20 degrees C and at pH 7.20, were found to be about 0.85 mM and 23 nmoles/min x mg protein, respectively) and proves to be inhibited by D-ornithine, inorganic phosphate, praseodimium chloride and mersalyl. Neither malate nor glutamate, but phosphate was found to exchange with ornithine. Phosphate efflux caused by externally added ornithine was shown both as revealed by a c colorimetric assay and as continuously monitored by measuring extramitochondrial reduction of NAD+ in the presence of glyceraldehyde-3-phosphate, glyceraldehyde-3-phosphate dehydrogenase, ADP and 3-phosphoglycerate kinase. The role of ornithine carrier in kidney metabolism will also be discussed.     

Coenzyme A enhances activity of the mitochondrial adenine nucleotide translocator

The adenine nucleotide translocator (ANT) accomplishes the exchange of ATP from the mitochondrial matrix with cytoplasmic ADP. While investigating the biochemical mechanism of retinoic acid (RA) on the ANT via retinoylation, we have found and subsequently demonstrated a positive influence of Coenzyme A (CoA) on the transport of ATP across the membranes of rat liver mitochondria. CoA enhances ANT activity in a dose-dependent manner modifying the V_max (673.3 ± 20.7 nmol ATP/mg protein/min versus 155.0 ± 1.9 nmol ATP/mg protein/min), the IC₅₀ for the specific inhibitor carboxyatractyloside (CATR) (0.142 ± 0.012 μM versus 0.198 ± 0.011 μM) but not the K_m (22.50 ± 0.52 μM versus 22.19 ± 0.98 μM). Data suggest a likely enzymatic involvement in the interaction between ANT and CoA. The effect of CoA is observed in mitochondria from several different tissues.     

Bcl-rambo induces apoptosis via interaction with the adenine nucleotide translocator

The Bcl-2 family proteins plays a central role in apoptosis. The pro- or anti-apoptotic activities of Bcl-2 family are dependent on the Bcl-2 homology (BH) regions. Bcl-rambo, a new pro-apoptotic member, is unusual in that its pro-apoptotic activity is independent of its BH domains. However, the mechanism underlying Bcl-rambo-induced apoptosis is largely unknown. Mitochondrial localization is indispensable for the pro-apoptotic function of Bcl-rambo. Bcl-rambo interacts physically with the adenine nucleotide translocator (ANT), suppresses the ADT/ATP-dependent translocation activity of ANT. Collectively, our data indicate Bcl-rambo is a pro-apoptotic member of the Bcl-2 family, induces the permeability transition via interaction with ANT.

Structured summary of protein interactions:

Bcl-Rambo and HSP60colocalize by fluorescence microscopy (View interaction)Bcl-rambobinds to ANT1 by pull down (View interaction)     

Increase in the adenine nucleotide translocase content of duckling subsarcolemmal mitochondria during cold acclimation

Intermyofibrillar and subsarcolemmal mitochondria were isolated from duckling gastrocnemius muscle. The adenine nucleotide translocase (ANT) content of subsarcolemmal mitochondria was found to be half of that present in intermyofibrillar mitochondria. In addition, cold acclimation resulted in a 1.7-fold increase in subsarcolemmal mitochondrial ANT content, with intermyofibrillar mitochondrial ANT remaining constant. This change in mitochondrial ANT content correlates with the previously reported cold-induced change in the sensitivity of mitochondria to palmitate-inhibited ATP synthesis [Roussel et al. (1998) FEBS Lett. 439, 258-262]. It is suggested that the mitochondrial ANT content enhances or reduces the fatty acid uncoupling activity in tissue, depending on the energetic state of mitochondria.     

Modification by calcium ions of adenine nucleotide translocation in rat liver mitochondria

1. Added Ca(2+) stimulates the translocation of ATP by isolated rat liver mitochondria. 2. The apparent K(m) for added Ca(2+) in stimulating the translocation of 200mum-ATP is approx. 160mum (75mum ;free' Ca(2+)). 3. The greatest stimulation of ATP translocation by Ca(2+) occurs at the lower concentrations of ATP. 4. Sr(2+) (and to a lesser extent Ba(2+)) can replace Ca(2+) whereas Mg(2+) and Mn(2+) have only little ability to stimulate ATP translocation. 5. Translocation of dATP is also stimulated by Ca(2+) whereas that of ADP is stimulated to only a relatively small degree. 6. Studies with metabolic inhibitors and uncouplers provide evidence that stimulation by Ca(2+) and by uncouplers is additive and that the mechanism of Ca(2+) stimulation does not seem to involve the high-energy intermediate of oxidative phosphorylation. 7. In the presence of Ca(2+), ATP is able to effectively compete with ADP for translocation. 8. Added K(+) further enhances the ability of Ca(2+) to stimulate ATP translocation. 9. These findings are discussed in relation to the potential involvement of Ca(2+) in modifying enzymic reactions involved in the regulation of cell metabolism.