5 Roles Mitochondria Play in Cells
Traditionally referred to as the powerhouses of cells, mitochondria play a vital role in the conversion of energy from food into energy for biological processes. However, in recent years, a growing number of studies have demonstrated that mitochondria are also deeply involved in a range of other activities that enable cells to function efficiently and help to maintain a healthy body.
Here we take a look at 5 roles that mitochondria have been shown to play in cells, and what can happen when these processes are disturbed.
1. Production of ATP
Perhaps the most well-known role of mitochondria is the production of ATP, the energy currency of cells. This complex, multistep process, is essential for proper functioning of the body, and dysfunction can contribute to a variety of diseases ranging from diabetes to Parkinson’s Disease, to rare genetic disorders.
The greatest metabolic demand in the body is found in the outer retina, a site which also has a high concentration of mitochondria. A team of researchers from UCL demonstrated that a reduction in retinal ATP was associated with inflammation and the subsequent development of age-related macular degeneration. It is thought that similar declines in ATP production throughout the body could play a role in a number of other aspects of aging.
2. Calcium Homeostasis
Mitochondrial calcium exchange is the flow of calcium in and out of a cell’s mitochondria, a process important in metabolic regulation and cell death.
A recent paper published in April 2017, also identified that calcium efflux from mitochondria plays a vital role in heart function. Knocking out the gene encoding the mitochondrial sodium-calcium exchanger NCLX in mice was associated with sudden death from heart failure, whilst overexpression increased mitochondrial efflux and offered protection against heart failure progression. The findings suggest that NCLX maintains cardiomyocytes by regulating calcium efflux and preventing calcium overload induced cell death.
3. Regulation of Innate Immunity
Innate immunity is the in-born system that recognizes and responds to infection by pathogens, providing immediate, non-specific defence. Mitochondrial antiviral signalling protein (MAVS) plays a key role in the innate response to viral infections, helping to induce antiviral and anti-inflammatory pathways.
Disruption to MAVS can lead to a break down in immune protection – an increase in severe mortality and death from experimental colitis was seen in MAVS knockout mice compared to wild type animals.
4. Programmed Cell Death
Apoptosis is the highly controlled process of programmed cell death, which is used by multicellular organisms in a number of biological processes, including intrauterine development, mopping up damaged cells, and maintaining cell numbers. The production of apoptotic bodies which are engulfed by phagocytes can be activated by both an intrinsic and extrinsic pathway.
Mitochondria control the intrinsic pathway, releasing proteins such as cytochrome c from their intermembrance space in response to cell stresses such as heat, infection, hypoxia, increased calcium and nutrient deprivation. Disturbances to this regulation are associated with the development of diseases such as cancer, and tissue damage following stroke.
5. Stem Cell Regulation
Mitochondria are thought to play crucial roles in the maintenance of pluripotency, differentiation, and reprogramming of induced pluripotent stem cells.
The generation of reactive oxygen species (ROS) by mitochondria has been shown to regulate somatic stem cell fate - an increase in ROS is associated with a decrease in the regeneration potential of human mesenchymal stem cells and a move towards progenitor commitment and differentiation.
This handful of examples gives just a snapshot of the mighty influence that mitochondria can have on cell function and health. The continued discovery of these intricacies, and the mechanisms involved in mitochondrial dysfunction, should lead to the development of new and improved therapies for a wide range of diseases.