Mitochondrial ATP synthase c-subunit leak channel triggers cell death upon loss of its F1 subcomplex

Abstract

Mitochondrial ATP synthase is vital not only for cellular energy production but also for energy dissipation and cell death. ATP synthase c-ring was suggested to house the leak channel of mitochondrial permeability transition (mPT), which activates during excitotoxic ischemic insult. In this present study, we purified human c-ring from both eukaryotic and prokaryotic hosts to biophysically characterize its channel activity. We show that purified c-ring forms a large multi-conductance, voltage-gated ion channel that is inhibited by the addition of ATP synthase F1 subcomplex. In contrast, dissociation of F1 from FO occurs during excitotoxic neuronal death suggesting that the F1 constitutes the gate of the channel. mPT is known to dissipate the osmotic gradient across the inner membrane during cell death. We show that ATP synthase c-subunit knock down (KD) prevents the osmotic change in response to high calcium and eliminates large conductance, Ca2+ and CsA sensitive channel activity of mPT. These findings elucidate the gating mechanism of the ATP synthase c-subunit leak channel (ACLC) and suggest how ACLC opening is regulated by cell stress in a CypD-dependent manner.

Permeability transition pore-related changes in the proteome and channel activity of ATP synthase dimers and monomers

“…3, Datasets_S01-S07) and, in accordance with recent observations, reduced the F-ATP synthase stability and/or in gel activity after separation (Fig. 1) [44,45], it, however, drastically inhibited the channel activity of eluted F-ATP synthase (Fig. 2).…”

“…4). (Separation of membrane-immersed subcomplex from the matrix-oriented soluble subcomplex during the PTP opening was confirmed in recent works [44,45].) If this assumption is correct, the molecular mass of the PTP complex should be at least 270-300 kDa and hardly exceed 500 kDa.…”

Understanding the Dynamics of the Transient and Permanent Opening Events of the Mitochondrial Permeability Transition Pore with a Novel Stochastic Model

“…The mPTP is generally thought to be a large conductance channel (on the order of 1 nS) with multiple subconductance states [ 21 ]. However, it is also possible that the smaller and larger conductances represent separate physical processes, as suggested recently [ 22 ]. Previous studies have suggested that fA currents are sufficient to depolarize mitochondria [ 23 ].…”

Both ANT and ATPase are essential for mitochondrial permeability transition but not depolarization

“…Compelling evidence from several independent laboratories supports competing interpretations suggesting that a core part of PTP involves either the ATP synthase complex or ANT, both of which could be transformed into the high-conductance pore. 5 , 11 , 14 , 15 , 16 , 35 In both cell types lacking either ATPase or ANT, calcium treatment causes calcium release and membrane depolarization that is inhibited by CSA. 6 , 8 Here, using the same knockout cell models, we observed the phenomena of membrane depolarization.…”