Formation of High-Conductive C Subunit Channels upon Interaction with Cyclophilin D.

Giuseppe Federico Amodeo,Natalya Krilyuk,Evgeny V. Pavlov

doi:10.3390/ijms222011022

Giuseppe Federico Amodeo, Natalya Krilyuk + Show 1 more

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https://doi.org/10.3390/ijms222011022

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Abstract

The c subunit of the ATP synthase is an inner mitochondrial membrane (IMM) protein. Besides its role as the main component of the rotor of the ATP synthase, c subunit from mammalian mitochondria exhibits ion channel activity. In particular, c subunit may be involved in one of the pathways leading to the formation of the permeability transition pore (PTP) during mitochondrial permeability transition (PT), a phenomenon consisting of the permeabilization of the IMM due to high levels of calcium. Our previous study on the synthetic c subunit showed that high concentrations of calcium induce misfolding into cross-β oligomers that form low-conductance channels in model lipid bilayers of about 400 pS. Here, we studied the effect of cyclophilin D (CypD), a mitochondrial chaperone and major regulator of PTP, on the electrophysiological activity of the c subunit to evaluate its role in the functional properties of c subunit. Our study shows that in presence of CypD, c subunit exhibits a larger conductance, up to 4 nS, that could be related to its potential role in mitochondrial toxicity. Further, our results suggest that CypD is necessary for the formation of c subunit induced PTP but may not be an integral part of the pore.

Highlights

Mitochondrial stress induced by high concentrations of calcium and/or reactive oxygen species leads to the permeabilization of the inner mitochondrial membrane (IMM), a phenomenon called permeability transition (PT) [1,2]
Despite permeability transition pore (PTP) ion conducting pores formed by these protein complexes exhibit different conductances, their involvement in the channel opening depends on the interaction with cyclophilin D (CypD), a mitochondrial chaperone and the specific target of cyclosporin A (CSA) [10]
This mechanism is supported by studies that showed that the c subunit alone is sufficient to induce PTP [6,12,14]

Summary

Introduction

Mitochondrial stress induced by high concentrations of calcium and/or reactive oxygen species leads to the permeabilization of the inner mitochondrial membrane (IMM), a phenomenon called permeability transition (PT) [1,2]. PT occurs through the opening of a large channel, namely the permeability transition pore (PTP), across the IMM that allows the free flow of small metabolites (up to 1.5 kDa) and ions causing the dissipation of the membrane potential and disruption of oxidative phosphorylation [3]. Other studies suggest a separate mechanism where amyloidogenic peptides are involved in the formation of PTP in aging-related disorders. Despite PTP ion conducting pores formed by these protein complexes exhibit different conductances, their involvement in the channel opening depends on the interaction with cyclophilin D (CypD), a mitochondrial chaperone and the specific target of cyclosporin A (CSA) [10]. The addition of CSA did not affect the channel activity, suggesting that CypD may be essential for the formation of PTP but is not a structural component of the pore itself

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