Post-Translational Oxidative Modification and Inactivation of Mitochondrial Complex I in Epileptogenesis

Abstract

Mitochondrial oxidative stress and damage have been implicated in the etiology of temporal lobe epilepsy, but whether or not they have a functional impact on mitochondrial processes during epilepsy development (epileptogenesis) is unknown. One consequence of increased steady-state mitochondrial reactive oxygen species levels is protein post-translational modification (PTM). We hypothesize that complex I (CI), a protein complex of the mitochondrial electron transport chain, is a target for oxidant-induced PTMs, such as carbonylation, leading to impaired function during epileptogenesis. The goal of this study was to determine whether oxidative modifications occur and what impact they have on CI enzymatic activity in the rat hippocampus in response to kainate (KA)-induced epileptogenesis. Rats were injected with a single high dose of KA or vehicle and evidence for CI modifications was measured during the acute, latent, and chronic stages of epilepsy. Mitochondrial-specific carbonylation was increased acutely (48 h) and chronically (6 week), coincident with decreased CI activity. Mass spectrometry analysis of immunocaptured CI identified specific metal catalyzed carbonylation to Arg76 within the 75 kDa subunit concomitant with inhibition of CI activity during epileptogenesis. Computational-based molecular modeling studies revealed that Arg76 is in close proximity to the active site of CI and carbonylation of the residue is predicted to induce substantial structural alterations to the protein complex. These data provide evidence for the occurrence of a specific and irreversible oxidative modification of an important mitochondrial enzyme complex critical for cellular bioenergetics during the process of epileptogenesis.

Identification and characterization of novel mutations implicated in congenital fibrinogen disorders

“…The ZRank scoring function was used to calculate the interaction energies of the resulting predicted protein complexes and represents a combination of van der Waals attractive and repulsive energies, short and long range repulsive and attractive energies, and desolvation 24. Similarity of the predicted protein complexes to the crystal structure (1FZB) was determined by calculating the root mean square deviation (RMSD) using the crystal structure as the reference 25. The three poses with the lowest RMSD values (ie, the greatest similarity to the crystal structure) were selected from each group for the energy comparison.…”

Pathophysiology of status epilepticus

“…As previously described ROS and consequent peroxynitrite formation can contribute to cell death though lipid peroxidation, inactivation of enzymes, mPTP opening and DNA damage. Moreover, ROS can directly inhibit mitochondrial complex 1 activity, further impeding ATP production [85,86]. ROS induced DNA damage can lead to activation of poly (ADP-ribose) polymerase (PARP), a repair enzyme.…”

Mitochondrial respiration deficits driven by reactive oxygen species in experimental temporal lobe epilepsy

“…In studies of patients with TLE, the role of mitochondria has been suggested by inhibition of complex I of the electron transport chain (ETC) and reduction in N-acetyl aspartate levels in the hippocampus (Kunz et al, 2000; Vielhaber et al, 2008). Recent work from our group has shown increases in production of mitochondrial ROS, reactive nitrogen species (RNS), oxidative damage to oxidant-sensitive mitochondrial proteins (aconitase and complex I) and glutathione depletion in animal models of TLE (Jarrett et al, 2008; Waldbaum et al, 2010; Ryan et al, 2012, 2013). Increased mitochondrial ROS and oxidative damage to ETC enzymes suggests that mitochondrial respiration may be impaired in TLE.…”