Mitochondrial permeability transition pore induction is linked to formation of the complex of ATPase C-subunit, polyhydroxybutyrate and inorganic polyphosphate.

P A Elustondo,M Nichols,G S Robertson,E V Pavlov,A Thirumaran,A Negoda,E Zakharian

doi:10.1038/cddiscovery.2016.70

Abstract

Mitochondrial permeability transition pore (mPTP) opening allows free movement of ions and small molecules leading to mitochondrial membrane depolarization and ATP depletion that triggers cell death. A multi-protein complex of the mitochondrial ATP synthase has an essential role in mPTP. However, the molecular identity of the central 'pore' part of mPTP complex is not known. A highly purified fraction of mammalian mitochondria containing C-subunit of ATPase (C-subunit), calcium, inorganic polyphosphate (polyP) and polyhydroxybutyrate (PHB) forms ion channels with properties that resemble the native mPTP. We demonstrate here that amount of this channel-forming complex dramatically increases in intact mitochondria during mPTP activation. This increase is inhibited by both Cyclosporine A, an inhibitor of mPTP and Ruthenium Red, an inhibitor of the Mitochondrial Calcium Uniporter. Similar increases in the amount of complex formation occurs in areas of mouse brain damaged by ischemia-reperfusion injury. These findings suggest that calcium-induced mPTP is associated with de novo assembly of a channel comprising C-subunit, polyP and PHB.

Highlights

IntroductionMPTP activation is thought to have a major role in ischemic cell death associated with stroke and myocardial infarction
The mitochondrial permeability transition pore is a large, weakly selective channel found in the mitochondrial inner membrane.[1]
We proposed the possibility that mitochondrial permeability transition pore (mPTP) channel opening and its formation might be stimulated by mitochondrial calcium uptake,[12] which was consistent with previous works by Bernardi’s group.[18]

Summary

Introduction

MPTP activation is thought to have a major role in ischemic cell death associated with stroke and myocardial infarction. The mitochondrial permeability transition pore (mPTP) is a large, weakly selective channel found in the mitochondrial inner membrane.[1] Opening of the mPTP channel leads to a dramatic increase in the inner membrane permeability, dissipation of the mitochondrial membrane potential and disruption of ATP production that, if not reversed, can trigger cell death. This hypothesis is supported by the fact that administration of cyclosporine A, an mPTP inhibitor, reduces infarct volume following ischemiareperfusion injury in the heart.[2] these findings suggest that the mPTP is a viable and important drug target, therapeutic efforts in this field have been hampered by a poor understanding of the molecular organization of this channel. Compelling evidence from several laboratories suggest that the mPTP is associated with, or is an integral part, of a multi-protein complex formed by ATP synthase.[3,4,5,6] the C-subunit of ATP synthase, which can form channels in model membranes,[6] appears to be essential for mPTP opening.[5]

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