Hydroxynonenal-stimulated activity of the uncoupling protein in Acanthamoeba castellanii mitochondria under phosphorylating conditions

Abstract

The influence of 4-hydroxy-2-nonenal (HNE), a lipid peroxidation end product, on the activity of the amoeba Acanthamoeba castellanii uncoupling protein (AcUCP) in isolated phosphorylating mitochondria was studied. Under phosphorylating conditions, exogenously added HNE induced GTP-sensitive AcUCP-mediated mitochondrial uncoupling. The HNE-induced proton leak decreased the yield of oxidative phosphorylation in an HNE concentration-dependent manner. The present study describes how the contributions of ATP synthase and HNE-induced AcUCP in phosphorylating respiration vary when the rate of succinate oxidation is decreased by limiting succinate uptake or inhibiting complex III activity within the range of a constant membrane potential. In phosphorylating mitochondria, at a given HNE concentration (100 μM), the efficiency of AcUCP in mitochondrial uncoupling increased as the respiratory rate decreased because the AcUCP contribution remained constant while the ATP synthase contribution decreased with the respiratory rate. HNE-induced uncoupling can be inhibited by GTP only when ubiquinone is sufficiently oxidized, indicating that in phosphorylating A. castellanii mitochondria, the sensitivity of AcUCP activity to GTP depends on the redox state of the membranous ubiquinone.

4-Hydroxy-nonenal—A Bioactive Lipid Peroxidation Product

“…This G(m) increase is concentration-dependent and exhibits a typical saturation kinetics. In addition, for the amoeba Acanthamoeba castellani it was shown that the HNE induced UCP-mediated mitochondrial uncoupling is GTP-sensitive [ 228 ].…”

Direct and indirect targets of carboxyatractyloside, including overlooked toxicity toward nucleoside diphosphate kinase (NDPK) and mitochondrial H + leak

“…Therefore, the unloading of the H + gradient with the help of uninhibited AAC/UCP might provide the time needed to regenerate active AAC for ADP/ATP antiport via compensatory expression. Hydroxynonenal-stimulated uncoupling in mitochondria may occur under phosphorylating conditions (Woyda-Ploszczyca and Jarmuszkiewicz 2013 ), supporting the hypothesis that organelles fight to survive in response to a CATR-induced increase in the HNE level. The efficacy of this type of first-line antioxidant defense, i.e., prevention of respiratory chain overreduction and downstream detrimental effects, such as excessive ROS generation/lipid peroxidation, depends on the relative concentrations of effectors alleviating, e.g., CATR, and factors driving, e.g., HNE, H + translocation through AAC and UCP across IMM.…”

“… 2003 ; Parker et al. 2008 ; Woyda-Ploszczyca and Jarmuszkiewicz 2011 , 2012 , 2013 , 2014a , 2014b , 2017 ). Regarding the effectiveness of GDP and GTP in hindering UCP, GTP is a relatively stronger, more specific, and more ‘diagnostic' (physiological) blocker than GDP in different organisms (Woyda-Ploszczyca and Jarmuszkiewicz 2011 , 2014a , 2017 ).…”

“… 1989 ; Woyda-Ploszczyca and Jarmuszkiewicz 2014a , 2017 ), and some aldehydes, particularly HNE ( Figure 4(b) ) (Echtay et al. 2003 ; Woyda-Ploszczyca and Jarmuszkiewicz 2012 , 2013 , 2014b , 2017 ). However, the metabolite P-CoA blocks AAC dissipating activity (Andreyev et al.…”

Acanthamoeba castellanii STAT Protein

“…A. castellanii has been more thoroughly studied experimentally than most other free living amoebae. It has been used as a model organism for studies on the cytoskeleton, cell movement, gene regulation and mitochondrial bioenergetics [9] , [10] , [11] . The role of STATs previously found in slime molds has been assigned mostly to the development of multicellular structures that are facultatively formed by D. discoideum cells [12] .…”