Arginine 107 of yeast ATP synthase subunit g mediates sensitivity of the mitochondrial permeability transition to phenylglyoxal

Abstract

Modification with arginine-specific glyoxals modulates the permeability transition (PT) of rat liver mitochondria, with inhibitory or inducing effects that depend on the net charge of the adduct(s). Here, we show that phenylglyoxal (PGO) affects the PT in a species-specific manner (inhibition in mouse and yeast, induction in human and mitochondria). Following the hypotheses (i) that the effects are mediated by conserved arginine(s) and (ii) that the PT is mediated by the F-ATP synthase, we have narrowed the search to 60 arginines. Most of these residues are located in subunits α, β, γ, ϵ, a, and c and were excluded because PGO modification did not significantly affect enzyme catalysis. On the other hand, yeast mitochondria lacking subunit g or bearing a subunit g R107A mutation were totally resistant to PT inhibition by PGO. Thus, the effect of PGO on the PT is specifically mediated by Arg-107, the only subunit g arginine that has been conserved across species. These findings are evidence that the PT is mediated by F-ATP synthase.

Why F-ATP Synthase Remains a Strong Candidate as the Mitochondrial Permeability Transition Pore

“…The most recent hypothesis posits that it originates from a conformational change occurring on the F-ATP synthase after Ca 2+ binding, possibly by replacing Mg 2+ at the catalytic site (Giorgio et al, 2017 ). This proposal has been supported by genetic manipulation of F-ATP synthase (Bonora et al, 2013 ; Giorgio et al, 2013 ), by electrophysiological measurements (Giorgio et al, 2013 ; Alavian et al, 2014 ; Carraro et al, 2014 ; von Stockum et al, 2015 ), and by mutagenesis of specific residues of F-ATP synthase (Giorgio et al, 2017 ; Antoniel et al, 2018 ; Guo et al, 2018 ; Carraro et al, in press ). On the other hand, the Walker laboratory has challenged this hypothesis on the basis of studies where subunit c (He et al, 2017b ) or peripheral subunits b and OSCP (He et al, 2017a ) had been genetically ablated.…”

“…The effects of PGO are species-specific, and we recently identified R107 of F-ATP synthase subunit g as the unique PTP-modulating target of PGO in yeast. Remarkably, expression of human subunit g in yeast transferred the “human” PTP phenotype, suggesting that species-specificity depends on differences in the primary structure of F-ATP synthase (Guo et al, 2018 ). The importance of the e and g subunits in formation of the yeast channel is also supported by our recent finding that their deletion abrogated the high-conductance channels in mutants where dimerization was enforced by copper-dependent formation of dimers through oxidation of C23 of subunit a (Carraro et al, in press ).…”

High-Conductance Channel Formation in Yeast Mitochondria is Mediated by F-ATP Synthase e and g Subunits

“…and Mg 2+ at the catalytic site [51], confers resistance to Ca 2+ -induced PTP opening and cell death [14]; (iii) H112Q and H112Y mutations of OSCP subunit made the PTP/MMC totally refractory to inhibition by H + , the most effective PTP blockers [15]; and (iv) an R107A mutation of yeast subunit g completely blunted the effects of phenylglyoxal on the permeability transition [52]. On the other hand, genetic ablation of either the OSCP or b subunits [46] or of subunit c [53] led to the assembly of defective F-ATP synthase.…”

Mitochondrial Ca2+‐activated F1FO‐ATPase hydrolyzes ATP and promotes the permeability transition pore

“…Thus, Is‐F 1 selectively inhibits F 1 ‐ATPase activity and, consequently, its Ca 2+ ‐dependent ATP hydrolysis. Recent studies on the PTP, aiming at shedding light on the F 1 F O ‐ATPase subunit(s) involved in its formation, lead to two main hypotheses, namely that the PTP would form either inside the c ‐ring or between F 1 F O ‐ATPase monomers of a dimer . However, the molecular mechanism that triggers PTP formation is still enigmatic .…”