Dopamine quinone modifies and decreases the abundance of the mitochondrial selenoprotein glutathione peroxidase 4

Abstract

Oxidative stress and mitochondrial dysfunction are known to contribute to the pathogenesis of Parkinson's disease. Dopaminergic neurons may be more sensitive to these stressors because they contain dopamine (DA), a molecule that oxidizes to the electrophilic dopamine quinone (DAQ) which can covalently bind nucleophilic amino acid residues such as cysteine. The identification of proteins that are sensitive to covalent modification and functional alteration by DAQ is of great interest. We have hypothesized that selenoproteins, which contain a highly nucleophilic selenocysteine residue and often play vital roles in the maintenance of neuronal viability, are likely targets for the DAQ. Here we report the findings of our studies on the effect of DA oxidation and DAQ on the mitochondrial antioxidant selenoprotein Glutathione Peroxidase 4 (GPx4). Purified GPx4 could be covalently modified by DAQ, and the addition of DAQ to rat testes lysate resulted in dose dependent decreases in GPx4 activity and monomeric protein levels. Exposing intact rat brain mitochondria to DAQ resulted in similar decreases in GPx4 activity and monomeric protein levels as well as detection of multiple forms of DA-conjugated GPx4 protein. Evidence of both GPx4 degradation and polymerization was observed following DAQ exposure. Finally, we observed a dose dependent loss of mitochondrial GPx4 in differentiated PC12 cells treated with dopamine. Our findings suggest that a decrease in mitochondrial GPx4 monomer and a functional loss of activity may be a contributing factor to the vulnerability of dopaminergic neurons in Parkinson's disease.

In vivo protein targets for increased quinoprotein adduct formation in aged substantia nigra

“…Previous in vitro studies have identified various protein targets, including α-synuclein (Bisaglia et al, 2007(Bisaglia et al, , 2010Marques andOuteiro, 2012), parkin (LaVoie et al, 2005), DJ-1 (Girotto et al, 2012), tyrosine hydroxylase , superoxide dismutase 2 (SOD2) (Belluzzi et al, 2012), glutathione peroxidase 4 (GPx4) (Hauser et al, 2013), and a variety of mitochondrial proteins (Van Laar et al, 2009). However, the in vivo protein targets for quinone modification, particularly proteins with increased quinone modification in aged SN, were completely unknown.…”

“…While previous in vitro studies were mostly based on educated guess or labeling isolated mitochondria or cultured cells with 14 C-dopamine (Belluzzi et al, 2012;Bisaglia et al, 2007Bisaglia et al, , 2010Girotto et al, 2012;Hauser et al, 2013;; LaVoie et al, 2005; Marques and Outeiro, 2012; Van Laar et al, Fig. 8.…”

Protective and toxic roles of dopamine in Parkinson's disease

“…Recently, it has been reported that dopamine o ‐quinone forms adduct with mitochondrial glutathione peroxidase 4 (Hauser et al . ).…”

“…), mitochondrial glutathione peroxidase 4 (Hauser et al . ); dopamine transporter (Whitehead et al . ); quinoprotein adducts (Wang et al .…”

Selenium and selenoprotein function in brain disorders

“…DJ‐1, which is associated with a recessive form of PD, regulates translation of GPx4 , and oxidation of DJ‐1 increases GPx4 synthesis . Oxidation of dopamine to dopamine quinone, conversely, decreases GPx4 following modification with quinone residues . This could also explain the decrease in GPx1 and GPx4 by methamphetamine in a dopaminergic cell model .…”