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The properties of the mitochondrial F1FO‐ATPase catalytic site, which can bind Mg2+, Mn2+, or Ca2+ and hydrolyze ATP, were explored by inhibition kinetic analyses to cast light on the Ca2+‐activated F1FO‐ATPase connection with the permeability transition pore (PTP) that initiates cascade events leading to cell death. While the natural cofactor Mg2+ activates the F1FO‐ATPase in competition with Mn2+, Ca2+ is a noncompetitive inhibitor in the presence of Mg2+. Selective F1 inhibitors (Is‐F1), namely NBD‐Cl, piceatannol, resveratrol, and quercetin, exerted different mechanisms (mixed and uncompetitive inhibition) on either Ca2+‐ or Mg2+‐activated F1FO‐ATPase, consistent with the conclusion that the catalytic mechanism changes when Mg2+ is replaced by Ca2+. In a partially purified F1 domain preparation, Ca2+‐activated F1‐ATPase maintained Is‐F1 sensitivity, and enzyme inhibition was accompanied by the maintenance of the mitochondrial calcium retention capacity and membrane potential. The data strengthen the structural relationship between Ca2+‐activated F1FO‐ATPase and the PTP, and, in turn, on consequences, such as physiopathological cellular changes. [ABSTRACT FROM AUTHOR]

The recent introduction of the Asian yellow-legged hornet, Vespa velutina, into Europe has raised concern regarding the threat to honeybees and the competition with the European hornet, Vespa crabro. The aim of this study was to investigated essential (Mg, Fe, Zn, Cu) and non-essential (Cd and Pb) elements in these two species. Element concentrations were determined in the whole body and separately in the head, thorax and abdomen using atomic absorption spectrometry (AAS). The changes in essential element concentration and speciation during metamorphosis were also studied using size exclusion chromatography followed by AAS and proteomic analysis. In both species, the essential elements were more concentrated in the abdomen due to the presence of fat bodies. Magnesium, Fe and Zn concentrations were significantly higher in V. crabro than in V. velutina and could have been related to the higher aerobic energy demand of the former species required to sustain foraging flight. Low concentrations of Cd and Pb were indicative of low environmental exposure. The concentration and speciation of essential elements, particularly Fe, varied among the developmental stages, indicating a modification of ligand preferences during metamorphosis. Overall, the results in the present study provide a better understanding of the hornet metal metabolism and a foundation for additional studies. [ABSTRACT FROM AUTHOR]

Impaired mitochondria cause an impressive decrease in ATP production becoming a common condition of cardiovascular diseases. Myxomatous mitral valve disease (MMVD) is characterized by mitochondrial dysfunction. By a non-invasive procedure of metabolism analysis on peripheral blood mononuclear cells, we exploit ex-vivo studies that directly constitute a translational approach to evaluate the cell bioenergetics. Cell ATP production decreased in the presence of MMVD, whereas glycolysis was unaffected. In MMVD, the mitochondrial activity underwent a significant reduction of basal respiration, maximal respiration, and ATP production. Our results depicted a pathological condition of MMVD characterized by cell metabolism deprived of mitochondrial energy support., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Salvatore Nesci reports financial support was provided by University of Bologna. Chiara Bernardini reports financial support was provided by University of Bologna. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The mitochondrial permeability transition pore (PTP), which drives regulated cell death when Ca 2+ concentration suddenly increases in mitochondria, was related to changes in the Ca 2+ -activated F 1 F O -ATPase. The effects of the gadolinium cation (Gd 3+ ), widely used for diagnosis and therapy, and reported as PTP blocker, were evaluated on the F 1 F O -ATPase activated by Mg 2+ or Ca 2+ and on the PTP. Gd 3+ more effectively inhibits the Ca 2+ -activated F 1 F O -ATPase than the Mg 2+ -activated F 1 F O -ATPase by a mixed-type inhibition on the former and by uncompetitive mechanism on the latter. Most likely Gd 3+ binding to F 1 , is favoured by Ca 2+ insertion. The maximal inactivation rates (k inact ) of pseudo-first order inactivation are similar either when the F 1 F O -ATPase is activated by Ca 2+ or by Mg 2+ . The half-maximal inactivator concentrations (K I ) are 2.35 ± 0.35 mM and 0.72 ± 0.11 mM, respectively. The potency of a mechanism-based inhibitor (k inact /K I ) also highlights a higher inhibition efficiency of Gd 3+ on the Ca 2+ -activated F 1 F O -ATPase (0.59 ± 0.09 mM -1 ∙s -1 ) than on the Mg 2+ -activated F 1 F O -ATPase (0.13 ± 0.02 mM -1 ∙s -1 ). Consistently, the PTP is desensitized in presence of Gd 3+ . The Gd 3+ inhibition on both the mitochondrial Ca 2+ -activated F 1 F O -ATPase and the PTP strengthens the link between the PTP and the F 1 F O -ATPase when activated by Ca 2+ and provides insights on the biological effects of Gd 3+ ., (Copyright © 2021. Published by Elsevier B.V.)

In mammalian cells enzymatic and non-enzymatic pathways produce H 2 S, a gaseous transmitter which recently emerged as promising therapeutic agent and modulator of mitochondrial bioenergetics. To explore this topic, the H 2 S donor NaHS, at micromolar concentrations, was tested on swine heart mitochondria. NaHS did not affect the F 1 F O -ATPase activated by the natural cofactor Mg 2 , but, when Mg 2+ was replaced by Ca 2+ , a slight 15% enzyme inhibition at 100 µM NaHS was shown. Conversely, both the NADH-O 2 and succinate-O 2 oxidoreductase activities were totally inhibited by 200 μM NaHS with IC 50 values of 61.6 ± 4.1 and 16.5 ± 4.6 μM NaHS, respectively. Since the mitochondrial respiration was equally inhibited by NaHS at both first or second respiratory substrates sites, the H 2 S generation may prevent the electron transfer from complexes I and II to downhill respiratory chain complexes, probably because H 2 S competes with O 2 in complex IV, thus reducing membrane potential as a consequence of the cytochrome c oxidase activity inhibition. The Complex IV blockage by H 2 S was consistent with the linear concentration-dependent NADH-O 2 oxidoreductase inhibition and exponential succinate-O 2 oxidoreductase inhibition by NaHS, whereas the coupling between substrate oxidation and phosphorylation was unaffected by NaHS. Even if H 2 S is known to cause sulfhydration of cysteine residues, thiol oxidizing (GSSG) or reducing (DTE) agents, did not affect the F 1 F O -ATPase activities and mitochondrial respiration, thus ruling out any involvement of post-translational modifications of thiols. The permeability transition pore, the lethal channel which forms when the F 1 F O -ATPase is stimulated by Ca 2+ , did not open in the presence of NaHS, which showed a similar effect to ruthenium red, thus suggesting a putative Ca 2+ transport cycle inhibition., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The molecular mechanisms which rule the formation and opening of the mitochondrial permeability transition pore (mPTP), the lethal mechanism which permeabilizes mitochondria to water and solutes and drives the cell to death, are still unclear and particularly little investigated in invertebrates. Since Ca 2+ increase in mitochondria is accompanied by mPTP opening and the participation of the mitochondrial F 1 F O -ATPase in the mPTP is increasingly sustained, the substitution of the natural cofactor Mg 2+ by Ca 2+ in the F 1 F O -ATPase activation has been involved in the mPTP mechanism. In mussel midgut gland mitochondria the similar kinetic properties of the Mg 2+ - or Ca 2+ -dependent F 1 F O -ATPase activities, namely the same affinity for ATP and bi-site activation kinetics by the ATP substrate, in spite of the higher enzyme activity and coupling efficiency of the Mg 2+ -dependent F 1 F O -ATPase, suggest that both enzyme activities are involved in the bioenergetic machinery. Other than being a mitochondrial poison and environmental contaminant, sulfide at low concentrations acts as gaseous mediator and can induce post-translational modifications of proteins. The sulfide donor NaHS, at micromolar concentrations, does not alter the two F 1 F O -ATPase activities, but desensitizes the mPTP to Ca 2+ input. Unexpectedly, NaHS, under the conditions tested, points out a chemical refractoriness of both F 1 F O -ATPase activities and a failed relationship between the Ca 2+ -dependent F 1 F O -ATPase and the mPTP in mussels. The findings suggest that mPTP role and regulation may be different in different taxa and that the F 1 F O -ATPase insensitivity to NaHS may allow mussels to cope with environmental sulfide., Competing Interests: Declaration of interest None., (Copyright © 2020 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.)

The properties of the mitochondrial F 1 F O -ATPase catalytic site, which can bind Mg 2+ , Mn 2+ , or Ca 2+ and hydrolyze ATP, were explored by inhibition kinetic analyses to cast light on the Ca 2+ -activated F 1 F O -ATPase connection with the permeability transition pore (PTP) that initiates cascade events leading to cell death. While the natural cofactor Mg 2+ activates the F 1 F O -ATPase in competition with Mn 2+ , Ca 2+ is a noncompetitive inhibitor in the presence of Mg 2+ . Selective F 1 inhibitors (Is-F 1 ), namely NBD-Cl, piceatannol, resveratrol, and quercetin, exerted different mechanisms (mixed and uncompetitive inhibition) on either Ca 2+ - or Mg 2+ -activated F 1 F O -ATPase, consistent with the conclusion that the catalytic mechanism changes when Mg 2+ is replaced by Ca 2+ . In a partially purified F 1 domain preparation, Ca 2+ -activated F 1 -ATPase maintained Is-F 1 sensitivity, and enzyme inhibition was accompanied by the maintenance of the mitochondrial calcium retention capacity and membrane potential. The data strengthen the structural relationship between Ca 2+ -activated F 1 F O -ATPase and the PTP, and, in turn, on consequences, such as physiopathological cellular changes., (© 2019 New York Academy of Sciences.)