Mitochondria are essential components of almost all cells in plants, fungi, and animals. However, until now, their membranes have been assumed to be static in structure. But in a study published today in EMBO Reports, researchers discovered that the inner membranes of mitochondria are by no means static, but rather constantly change their structure every few seconds in living cells. This dynamic adaptation process further increases the performance of our cellular power plants.
“In our opinion, this finding fundamentally changes [our understanding of] the way our cellular power plants work and will probably change the textbooks,” says senior author Andreas Reichert of the HHU.
Mitochondria perform vital cellular functions including the regulated conversion of energy from food into ATP, which is the energy currency of cells. In an adult human, one molecule of ATP is produced about 20,000 times a day, followed by its consumption for energy utilization. This immense synthesis capacity takes place in the inner membrane of the mitochondria.
The inner membrane has numerous folds that are called cristae. Previously, it was assumed that a specific static structure of the cristae ensured the synthesis of ATP. But prior to this study, whether cristae membranes are able to dynamically adapt or alter their structure in living cells, to what extent this happens, and which proteins are required to do so were still unknown.
The researchers were able to show that cristae membranes in living cells continuously change their structure within the mitochondria. Their work also suggests that the cristae membrane dynamics depend on a recently identified protein complex, the MICOS complex. Malfunctions of the MICOS complex can lead to a number of serious diseases, such as Parkinson’s disease.
“Our now published observations lead to the model that cristae, after membrane fission, can exist for a short time as isolated vesicles within mitochondria and then re-fuse with the inner membrane,” Reichert says. “This enables an optimal and extremely rapid adaptation to the energetic requirements in a cell.”