Ca2+-Dependent Mitochondrial Permeability Transition Pore: Structure, Properties, and Role in Cellular Pathophysiology

The Mitochondrial Permeability Transition pore (MPT pore) activated by Ca²⁺ ions is a phenomenon that has long been the subject of intense study. Cyclophilin D-dependent opening of the MPT pore in mitochondria in response to calcium overload and oxidative stress leads to swelling of the mitochondrial matrix, depolarization of the inner membrane and dysregulation of ion homeostasis. These processes are accompanied by damage to mitochondrial membranes and, ultimately, to cell death. Despite decades of research, the molecular identity of the MPT pore remains unclear. Currently, the inner membrane proteins - ATP synthase and adenine nucleotide translocator (ANT) - are considered to be its key structural components, along with the regulatory protein cyclophilin D. The involvement of the MPT pore in the progression of various pathological conditions and diseases, as well as in a number of physiological processes, such as the regulation of cellular bioenergetics and rapid release of Ca²⁺, is widely discussed. This review summarizes modern molecular genetic data on the putative structure of the MPT pore, traces the evolution of views on its functioning - from interpreting it as a simple experimental artifact to its recognition as a putative key regulator of energy metabolism - and also considers the mechanisms of its regulation and its multifaceted pathophysiological role.