title: Forward operation of adenine nucleotide translocase during F0F1-ATPase reversal: critical role of matrix substrate-level phosphorylation.
abstract: In pathological conditions, F(0)F(1)-ATPase hydrolyzes ATP in an attempt to maintain mitochondrial membrane potential. Using thermodynamic assumptions and computer modeling, we established that mitochondrial membrane potential can be more negative than the reversal potential of the adenine nucleotide translocase (ANT) but more positive than that of the F(0)F(1)-ATPase. Experiments on isolated mitochondria demonstrated that, when the electron transport chain is compromised, the F(0)F(1)-ATPase reverses, and the membrane potential is maintained as long as matrix substrate-level phosphorylation is functional, without a concomitant reversal of the ANT. Consistently, no cytosolic ATP consumption was observed using plasmalemmal K(ATP) channels as cytosolic ATP biosensors in cultured neurons, in which their in situ mitochondria were compromised by respiratory chain inhibitors. This finding was further corroborated by quantitative measurements of mitochondrial membrane potential, oxygen consumption, and extracellular acidification rates, indicating nonreversal of ANT of compromised in situ neuronal and astrocytic mitochondria; and by bioluminescence ATP measurements in COS-7 cells transfected with cytosolic- or nuclear-targeted luciferases and treated with mitochondrial respiratory chain inhibitors in the presence of glycolytic plus mitochondrial vs. only mitochondrial substrates. Our findings imply the possibility of a rescue mechanism that is protecting against cytosolic/nuclear ATP depletion under pathological conditions involving impaired respiration. This mechanism comes into play when mitochondria respire on substrates that support matrix substrate-level phosphorylation.
authors.affiliation: Department of Medical Biochemistry, Semmelweis University, Tuzolto St. 37-47, Room 4.521, Budapest, Hungary 1094. chinopoulos.christos@eok.sote.hu
authors.forename: Christos
authors.initials: C
authors.lastname: Chinopoulos
authors.forename: Akos A
authors.initials: AA
authors.lastname: Gerencser
authors.forename: Miklos
authors.initials: M
authors.lastname: Mandi
authors.forename: Katalin
authors.initials: K
authors.lastname: Mathe
authors.forename: Beata
authors.initials: B
authors.lastname: Töröcsik
authors.forename: Judit
authors.initials: J
authors.lastname: Doczi
authors.forename: Lilla
authors.initials: L
authors.lastname: Turiak
authors.forename: Gergely
authors.initials: G
authors.lastname: Kiss
authors.forename: Csaba
authors.initials: C
authors.lastname: Konràd
authors.forename: Szilvia
authors.initials: S
authors.lastname: Vajda
authors.forename: Viktoria
authors.initials: V
authors.lastname: Vereczki
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Oh
authors.forename: Vera
authors.initials: V
authors.lastname: Adam-Vizi
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D053078:Membrane Potential, Mitochondrial; D008928:Mitochondria / Q000378:metabolism; D000226:Mitochondrial ADP, ATP Translocases / Q000378:metabolism*; D009474:Neurons; D010766:Phosphorylation; D006180:Proton-Translocating ATPases / Q000378:metabolism*; D011817:Rabbits; D051381:Rats; D017207:Rats, Sprague-Dawley; D013816:Thermodynamics
chemical_list: D000255:Adenosine Triphosphate; D000226:Mitochondrial ADP, ATP Translocases; D006180:Proton-Translocating ATPases