How mitochondria age
Biochemists have described the age-related degradation of cellular power plants
Researchers from several German research centers have found that aging leads to changes in the structure of mitochondria and protein structures that synthesize the protein ATP (a universal energy carrier in cells). Details are given in an article by scientists for the journal Proceedings of the National Academy of Sciences (Daum et al., Age-dependent dissociation of ATP synthase dimers and loss of inner-membrane cristae in mitochondria, in the public domain).
To find out how organelles change with age, the authors of the study used Podospora anserina fungal cells. First, the mitochondria were isolated, then frozen and shone through with a beam of electrons. When shooting, the scientists changed the direction of the beam to get pictures from different angles. Based on the obtained images, a three-dimensional model with a resolution of up to several nanometers was assembled. Detailed reconstruction of mitochondria revealed that with age, the inner membrane loses its protrusions, and this is due to changes in ATP synthase.
Three-dimensional reconstruction of mitochondria (from an article in PNAS)
ATP synthase is a protein complex that is located on the inner membrane of the mitochondria. Its molecules are embedded in the membrane itself and form a channel through which hydrogen ions accumulated in the cavity between the two mitochondrial membranes pass into the inner space called the matrix. One of the parts of the complex rotates around its axis due to this ion current, and it also uses the energy accumulated by the ions to synthesize ATP molecules. In a young cell, ATP synthases form pairs that are located at a short distance from each other and thereby bend the cell membrane, but over time such pairs become smaller. The number of folds of the membrane decreases, as a result, instead of a complex structure, it turns into a relatively smooth two-layer bubble. Moreover, the walls of this bubble, as microtomography has shown, are often adjacent to each other.
All the described changes, as scientists say, lead to a decrease in the efficiency of the energy centers of the cell and, as a result, to metabolic disorders at the level of the body as a whole. However, the paper does not claim that this is the only or at least the key element of aging. Most researchers recognize aging as a multifactorial process that is studied on a variety of organisms from naked diggers (rodents with abnormally high life expectancy and practically cancer-free) to roundworms and even fungi.
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