energy crisis. Mutant huntingtin protein can interfere with mitochondrial energy production (orange).
The first signs of the disease Huntington's disease occurs in middle age: Jerks and muscle spasms are followed over the years by the worsening of memory and loss muscle control. Although a mutated gene is to blame, it is not clear how it causes symptoms. Now scientists studying mice and human cells affected by Huntington's disease have shown that chronic damage to mitochondria, cells of the plants plays an important role.
Huntington's disease is inherited by a person over 10 000 in the United States. The mutated gene adds unusually long chains of glutamine, an amino acid in a protein huntingtin (htt), and in general, the more glutamine chains corresponding to an earlier onset and more severe neurological symptoms. But scientists still do not know for sure what normal htt made or how the abnormal version of throws a wrench in the works.
neurologist and biochemist Timothy Greenamyre Alexander Panov from Emory University School of Medicine in Atlanta and his colleagues believe that mitochondria are an important factor in Huntington's disease. Mitochondria of the team examined are from mouse and human cells affected by Huntington's disease. They found that the long chains of glutamine in the stick abnormally htt protein in the outer membrane of mitochondria and allow ions to flow freely in and out. Accordingly, mitochondria "run" like a battery exploited, reports the team in the July 1st issue of Nature Neuroscience . In addition, Greenamyre and Panov found that pepper mitochondria with too much glutamine can not properly regulate calcium, which can reach toxic levels and kill the cell
But all body tissues htt -. So why the abnormal protein hit the cells of the nervous system so hard? Probably because neurons live so long, said Panov. As cells age, their mitochondria become less efficient. This problem is particularly acute for neurons because they are not often replaced as cells elsewhere. The subtle mitochondrial damage caused by mutant htt can exacerbate the wear and tear of natural aging, said Panov. This could explain why the disease remains at rest until the Middle Ages.
The debate on the role of mitochondrial damage in Huntington's disease fluctuated for years between scientists, says neurologist Kenneth Fischbeck of the National Institute of Neurological Disorders and Stroke in Bethesda, Maryland. "But this research should help resolve the issue and to focus the research."
Related Sites
The site of Timothy Greenamyre
The site Kenneth Fischbeck
Information about Huntington's Disease from the National Institute of Neurological Disorders and Stroke
Disease Huntington Society of America
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