Definition of Mitochondrial Dynamics

Angel Zamora Ramirez
Degree in physics

Mitochondrial dynamics is the set of processes through which mitochondria shape the morphology of a cell's mitochondrial network.

In the literature It is common for the mitochondria to appear as an oval-shaped organelle that has the task of supplying energy to the cell in the form of ATP. This simplified model of the mitochondria is helpful in locating it as part of the cell, however it also gives a somewhat misleading picture of the mitochondria in the cell.

Contrary to what is generally shown, the number of mitochondria varies from one tissue to another, tissues with high energy consumption. such as skeletal muscle and cardiac muscle have a greater number of mitochondria than those that do not need as much energy. In addition, mitochondria are capable of forming networks and subpopulations within the same cell. The mitochondrial network is capable of adapting to the metabolic demands of the cell, this adaptation is achieved thanks to "mitochondrial dynamics", which is composed of the processes of "fusion" and "fission" mitochondrial.

mitochondrial fusion

Mitochondrial fusion occurs when two mitochondria fuse to form one larger, elongated mitochondria. Mitochondria have two membranes, an outer membrane and an inner membrane. In the fusion process both membranes have to come together to generate a larger mitochondria. In mammals, mitochondrial fusion takes place thanks to proteins Mfn1 and Mfn2 that are responsible for the fusion of the outer membranes and the OPA 1 protein that fuses the inner membranes.

The matrix is ​​the space delimited by the inner membrane of the mitochondria, in it is the dna mitochondrial, certain proteins and organic ions, among other things. When two mitochondria fuse, the contents of their matrices are also shared. Thus, it is thought that one of the functions of mitochondrial fusion is to keep mitochondria in a state optimal for the production of ATP, in addition, the fusion allows a more united and elongated shape to be given to the mitochondrial network of the cell.

mitochondrial fission

Opposite to mitochondrial fusion is mitochondrial fission. This process occurs when a mitochondrion fragments to give rise to two smaller mitochondria. Mitochondrial fission in mammals occurs thanks to the intervention of the Drp1 protein, this protein accumulates at certain specific sites on the outer membrane of the mitochondria and “squeezes” it until it is cut and two smaller mitochondria are obtained.

One of the functions of mitochondrial fission is the transport of mitochondria from one part of the cell to another, since smaller mitochondria are easier to transport. Also, fission can serve to exclude from the mitochondrial network those mitochondria that no longer function properly and are subsequently degraded.

Mitochondrial quality control

He maintenance of the mitochondrial network is of vital importance to ensure the proper functioning of the metabolismcell phone. Mitochondrial DNA is especially susceptible to damage and mutations because it does not have protective mechanisms like nuclear DNA. Damage to mitochondrial DNA and other conditions such as oxidative stress can cause mitochondria to not function properly.

In order to deal with this, there is a control of quality which is largely shaped by mitochondrial dynamics. Continuous cycles of fusion and fission help repair the mitochondrial network and secrete dysfunctional mitochondria that affect the cell. Dysfunctional mitochondria are broken down through another process called "mitophagy." In this way, it is ensured that the mitochondrial network is composed mostly of mitochondria. functional.

Mitochondrial dynamics and pathologies

Various pathological conditions have been associated with a malfunction of mitochondrial dynamics. Certain types of Charcot-Marie-Tooth Disease have been associated with mutations in the gene encoding the mitochondrial fusion protein Mfn2. Various mutations in the gene encoding OPA1 have been associated with Optic Atrophy, the most common hereditary optic neuropathy. Also, conditions that affect metabolism, such as obesity or metabolic syndrome, have been related to the mitochondrial dysfunction and with an imbalance in mitochondrial dynamics resulting in a stronger mitochondrial network. fragmented.

Mitochondrial dynamics and exercise

Skeletal muscle is one of the tissues with the largest number of mitochondria due to the large amount of energy it requires. Exercise especially stimulates skeletal muscle and has been shown to be capable of modifying mitochondrial dynamics in this tissue.

Various studies show that exercise increases mitochondrial fusion in skeletal muscle. In addition, it is capable of stimulating the degradation of dysfunctional mitochondria through mitophagy and increasing the number of mitochondria present in skeletal muscle. All these effects reinforce the usefulness of exercise in preventing and combating obesity and metabolic syndrome.