A mitochondrion (pl. mitochondria) is an organelle found in the cells of most eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is used throughout the cell as a source of chemical energy. They were discovered by Albert von Kölliker in 1857 in the voluntary muscles of insects. Meaning a thread-like granule, the term mitochondrion was coined by Carl Benda in 1898. The mitochondrion is popularly nicknamed the "powerhouse of the cell", a phrase popularized by Philip Siekevitz in a 1957 Scientific American article of the same name.
Mitochondrial disease is a group of disorders caused by mitochondrial dysfunction. Mitochondria are the organelles that generate energy for the cell and are found in every cell of the human body except red blood cells. They convert the energy of food molecules into the ATP that powers most cell functions.
Suramin is a medication used to treat African sleeping sickness and river blindness. It is the treatment of choice for sleeping sickness without central nervous system involvement. It is given by injection into a vein.
Autism spectrum disorder (ASD) is a neurodevelopmental disorder that begins in early childhood, persists throughout adulthood, and affects two crucial areas of development: social communication and restricted, repetitive patterns of behavior. There are many conditions comorbid to autism spectrum disorder such as attention-deficit hyperactivity disorder and epilepsy.
Human mitochondrial genetics is the study of the genetics of human mitochondrial DNA. The human mitochondrial genome is the entirety of hereditary information contained in human mitochondria. Mitochondria are small structures in cells that generate energy for the cell to use, and are hence referred to as the "powerhouses" of the cell.
Cardiolipin is an important component of the inner mitochondrial membrane, where it constitutes about 20% of the total lipid composition. It can also be found in the membranes of most bacteria. The name "cardiolipin" is derived from the fact that it was first found in animal hearts. It was first isolated from the beef heart in the early 1940s by Mary C. Pangborn. In mammalian cells, but also in plant cells, cardiolipin (CL) is found almost exclusively in the inner mitochondrial membrane, where it is essential for the optimal function of numerous enzymes that are involved in mitochondrial energy metabolism.
Mitochondrial myopathies are types of myopathies associated with mitochondrial disease. Adenosine triphosphate (ATP), the chemical used to provide energy for the cell, cannot be produced sufficiently by oxidative phosphorylation when the mitochondrion is either damaged or missing necessary enzymes or transport proteins. With ATP production deficient in mitochondria, there is an over-reliance on anaerobic glycolysis which leads to lactic acidosis either at rest or exercise-induced.
Tafazzin is a protein that in humans is encoded by the TAFAZZIN gene. Tafazzin is highly expressed in cardiac and skeletal muscle, and functions as a phospholipid-lysophospholipid transacylase. It catalyzes remodeling of immature cardiolipin to its mature composition containing a predominance of tetralinoleoyl moieties. Several different isoforms of the tafazzin protein are produced from the TAFAZZIN gene. A long form and a short form of each of these isoforms is produced; the short form lacks a hydrophobic leader sequence and may exist as a cytoplasmic protein rather than being membrane-bound. Other alternatively spliced transcripts have been described but the full-length nature of all these transcripts is not known. Most isoforms are found in all tissues, but some are found only in certain types of cells. Mutations in the TAFAZZIN gene have been associated with mitochondrial deficiency, Barth syndrome, dilated cardiomyopathy (DCM), hypertrophic DCM, endocardial fibroelastosis, left ventricular noncompaction (LVNC), breast cancer, papillary thyroid carcinoma, non-small cell lung cancer, glioma, gastric cancer, thyroid neoplasms, and rectal cancer.
Apoptosis inducing factor is involved in initiating a caspase-independent pathway of apoptosis by causing DNA fragmentation and chromatin condensation. Apoptosis inducing factor is a flavoprotein. It also acts as an NADH oxidase. Another AIF function is to regulate the permeability of the mitochondrial membrane upon apoptosis. Normally it is found behind the outer membrane of the mitochondrion and is therefore secluded from the nucleus. However, when the mitochondrion is damaged, it moves to the cytosol and to the nucleus. Inactivation of AIF leads to resistance of embryonic stem cells to death following the withdrawal of growth factors indicating that it is involved in apoptosis.
Ellen Heber-Katz is an American immunologist and regeneration biologist who is a professor at Lankenau Institute for Medical Research (LIMR). She discovered that the Murphy Roths Large (MRL) mouse strain can regenerate wounds without scarring and can fully restore damaged tissues. Her work on regeneration has been extended into National Cancer Institute (NCI)-funded studies of novel aspects of breast cancer causation. Her research interests include immunology, regenerative medicine, and cancer.
Frataxin is a protein that in humans is encoded by the FXN gene.
Succinyl-CoA ligase [GDP-forming] subunit alpha, mitochondrial is an enzyme that in humans is encoded by the SUCLG1 gene.
Iron-sulfur cluster assembly enzyme ISCU, mitochondrial is a protein that in humans is encoded by the ISCU gene. It encodes an iron-sulfur (Fe-S) cluster scaffold protein involved in [2Fe-2S] and [4Fe-4S] cluster synthesis and maturation. A deficiency of ISCU is associated with a mitochondrial myopathy with lifelong exercise intolerance where only minor exertion causes tachycardia, shortness of breath, muscle weakness and myalgia.
Metabolic myopathies are myopathies that result from defects in biochemical metabolism that primarily affect muscle. They are generally genetic defects that interfere with the ability to create energy, causing a low ATP reservoir within the muscle cell.
Mitophagy is the selective degradation of mitochondria by autophagy. It often occurs to defective mitochondria following damage or stress. The process of mitophagy was first described in 1915 by Margaret Reed Lewis and Warren Harmon Lewis. Ashford and Porter used electron microscopy to observe mitochondrial fragments in liver lysosomes by 1962, and a 1977 report suggested that "mitochondria develop functional alterations which would activate autophagy." The term "mitophagy" was in use by 1998.
Mitochondrial biogenesis is the process by which cells increase mitochondrial numbers. It was first described by John Holloszy in the 1960s, when it was discovered that physical endurance training induced higher mitochondrial content levels, leading to greater glucose uptake by muscles. Mitochondrial biogenesis is activated by numerous different signals during times of cellular stress or in response to environmental stimuli, such as aerobic exercise.
Mitochondrial fission factor (Mff) is a protein that in humans is encoded by the MFF gene. Its primary role is in controlling the division of mitochondria. Mitochondrial morphology changes by continuous fission in order to create interconnected network of mitochondria. This activity is crucial for normal function of mitochondria. Mff is anchored to the mitochondrial outer membrane through the C-terminal transmembrane domain, extruding the bulk of the N-terminal portion containing two short amino acid repeats in the N-terminal half and a coiled-coil domain just upstream of the transmembrane domain into the cytosol. It has also been shown to regulate peroxisome morphology.
Mitochondria are dynamic organelles with the ability to fuse and divide (fission), forming constantly changing tubular networks in most eukaryotic cells. These mitochondrial dynamics, first observed over a hundred years ago are important for the health of the cell, and defects in dynamics lead to genetic disorders. Through fusion, mitochondria can overcome the dangerous consequences of genetic malfunction. The process of mitochondrial fusion involves a variety of proteins that assist the cell throughout the series of events that form this process.
The mitochondrial ribosome, or mitoribosome, is a protein complex that is active in mitochondria and functions as a riboprotein for translating mitochondrial mRNAs encoded in mtDNA. The mitoribosome is attached to the inner mitochondrial membrane. Mitoribosomes, like cytoplasmic ribosomes, consist of two subunits — large (mt-LSU) and small (mt-SSU). Mitoribosomes consist of several specific proteins and fewer rRNAs. While mitochondrial rRNAs are encoded in the mitochondrial genome, the proteins that make up mitoribosomes are encoded in the nucleus and assembled by cytoplasmic ribosomes before being implanted into the mitochondria.
The citrate-malate shuttle is a series of chemical reactions, commonly referred to as a biochemical cycle or system, that transports acetyl-CoA in the mitochondrial matrix across the inner and outer mitochondrial membranes for fatty acid synthesis. Mitochondria are enclosed in a double membrane. As the inner mitochondrial membrane is impermeable to acetyl-CoA, the shuttle system is essential to fatty acid synthesis in the cytosol. It plays an important role in the generation of lipids in the liver.
