A research group from the Faculty of Medicine at the University of Geneva understands the activity of a messenger protein and confirms the interaction governing relationships between various cellular elements, while demonstrating the primordial role played by a protein .
The latter, mitofusin 2, is responsible for transmitting information within the cell. When this protein is altered, messages sent by the cell’s "general management" are poorly received. Such a defect is found notably in Charcot-Marie-Tooth syndrome type II, a disease affecting nerve cells. This discovery, published in the latest issue of the journal Nature, opens up new avenues of research and opens up new therapeutic prospects in the field of neurodegenerative diseases. The nucleus of a cell is surrounded by a network of membranes, of which the endosplasmic reticulum (ER) is the essential component. In the cell, the ER plays several roles: molecule storage, cell detoxification and, above all, calcium metabolism. Very small, capsule-shaped structures, located not far from the ER and called mitochondria, are essential for cellular energy production. These two cellular entities, the mitochondria and the ER, act to control the life and death of the cell. However, until now, scientists had been unable to demonstrate their link: the team led by Luca Scorrano, Professor at the UNIGE Faculty of Medicine, has now succeeded in understanding the physical interaction between these two structures.
Communication is key
The cell can be compared to a large company where the mitochondria and the ER are independent departments. If a piece of information, urgent for the cell’s survival, is sent from the general management, it is imperative that it reaches all the departments as quickly as possible and, above all, in its entirety, so that they can each process it at their own level. The cell works in exactly this way, transmitting information via a network that optimizes its reception.
A sms transmitter in the body
Messages sent by the cell to the mitochondria are broadcast from the ER, like "text messages", via the pathway used by calcium. It seems that the quality of reception of the messages sent depends essentially on the distance between the mitochondria and the ER: distant from the latter, the former are less receptive to the signals sent by the cell, and no longer respond to the instructions provided by the "general management". This phenomenon can be found in numerous pathologies.
Altered protein, poor transmission
This physical connection between mitochondria and endoplasmic reticulum is orchestrated by a certain protein: mitofusin 2. Until recently, scientists thought that this protein only had a structural effect, acting on the size and shape of mitochondria. At the Department of Cell Physiology and Metabolism of the UNIGE Faculty of Medicine, Luca Scorrano has understood the essential function of this protein for cell survival, since it is responsible for ensuring the right proximity between the ER and mitochondria. When mitofusin 2 is altered, the distance between the mitochondria and the ER increases. And, in cells deficient in mitofusin 2, the transmission of information via the calcium pathway loses amplitude: the "sms" no longer get through. This discovery further confirms specialists’ intuition as to the importance of the interaction between ER and mitochondria in cell survival. This discovery opens up new avenues for research into Charcot-Marie-Tooth syndrome type II (which affects one in 10,000 people), into ways of treating this neuropathology, and into other genetic and neurodegenerative diseases.
