Persistence of the permeability transition pore in human mitochondria devoid of an assembled ATP synthase

Abstract

The opening of the permeability transition pore, a nonspecific channel in inner mitochondrial membranes, is triggered by an elevated total concentration of calcium ions in the mitochondrial matrix, leading to disruption of the inner membrane and necrotic cell death. Cyclosporin A inhibits pore opening by binding to cyclophilin D, which interacts with the pore. It has been proposed that the pore is associated with the ATP synthase complex. Previously, we confirmed an earlier observation that the pore survives in cells lacking membrane subunits ATP6 and ATP8 of ATP synthase, and in other cells lacking the enzyme’s c8rotor ring or, separately, its peripheral stalk subunits b and oligomycin sensitive conferral protein. Here, we investigated whether the pore is associated with the remaining membrane subunits of the enzyme. Individual deletion of subunits e, f, g, and 6.8-kDa proteolipid disrupts dimerization of the complex, and deletion of DAPIT (diabetes-associated protein in insulin sensitive tissue) possibly influences oligomerization of dimers, but removal of each subunit had no effect on the pore. Also, we removed together the enzyme’s membrane bound c8ring and the δ-subunit from the catalytic domain. The resulting cells assemble only a subcomplex derived from the peripheral stalk and membrane-associated proteins. Despite diminished levels of respiratory complexes, these cells generate a membrane potential to support uptake of calcium into the mitochondria, leading to pore opening, and retention of its characteristic properties. It is most unlikely that the ATP synthase, dimer or monomer, or any component, provides the permeability transition pore.

mPTP Proteins Regulated by Streptozotocin-Induced Diabetes Mellitus Are Effectively Involved in the Processes of Maintaining Myocardial Metabolic Adaptation

“…However, there are inconsistent views on whether the role of ATP synthase can be switched from a key energy-producing enzyme to an energy-dissipating channel, leading to cell death [23,42]. Moreover, a study by Carroll et al [43] cast doubt on the assumption that ATP synthase is the main structural component, because mPTPs were able to open after the deletion of selected ATP synthase subunits. CypD is a critical regulator of mPTPs and directly binds to the pore constituents, including ATP synthase and ADT, in order to facilitate mPTP opening [44].…”

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

“…Even if recent evidence on the PTP persistence in the presence of defective F 1 F O ‐ATPases apparently rules out any involvement of the enzyme in the PTP, the question is still open. Carroll et al .…”

“…Even if recent evidence on the PTP persistence in the presence of defective F 1 F O ‐ATPases apparently rules out any involvement of the enzyme in the PTP, the question is still open. Carroll et al . report that in the presence of defective F 1 F O ‐ATPases, the PTP forms and may deeply affect mitochondrial morphology and the structure of the cristae.…”

Translational issues for mitoprotective agents as adjunct to reperfusion therapy in patients with ST‐segment elevation myocardial infarction

“…cyclosporine A, ischaemia, mitochondria, myocardial infarction, reperfusion et al have proposed that mitochondrial ATP synthase could be the true molecular entity of the MPTP, although this hypothesis remains controversial. 28,29…”