Panov Alexander V, Burke James R, Strittmatter Warren J, Greenamyre J Timothy
Emory Center for Neurodegenerative Diseases, Emory University School of Medicine, Whitehead Biomedical Research Building, 615 Michael Street, Room 575, Atlanta, GA 30322, USA.
Arch Biochem Biophys. 2003 Feb 1;410(1):1-6. doi: 10.1016/s0003-9861(02)00585-4.
The mechanisms by which neurons die in CAG triplet repeat (polyglutamine) disorders, such as Huntington's disease, are uncertain; however, mitochondrial dysfunction and disordered calcium homeostasis have been implicated. We previously demonstrated abnormal mitochondrial calcium handling in Huntington's disease cell lines and transgenic mice. To examine whether these abnormalities might arise in part from direct effects of the expanded polyglutamine tract contained in mutant huntingtin, we have exposed normal rat liver and human lymphoblast mitochondria to glutathione S-transferase fusion proteins containing polyglutamine tracts of 0, 19, or 62 residues. Similar to bovine serum albumin, each of the protein constructs nonspecifically inhibited succinate-supported respiration, independent of polyglutamine tract length. There was a small but significant reduction of mitochondrial membrane potential (state 4) only in the presence of the pathological-length polyglutamine tract. With successive addition of small Ca(2+) aliquots, mitochondria exposed to pathological-length polyglutamine tracts (approximately 5 microM) depolarized much earlier and to a greater extent than those exposed to the other protein constructs. These results suggest that the mitochondrial calcium handling defects seen in Huntington's disease cell lines and transgenic mice may be due, in part, to direct, deleterious effects of mutant huntingtin on mitochondria.
在CAG三联体重复（多聚谷氨酰胺）疾病（如亨廷顿舞蹈症）中，神经元死亡的机制尚不清楚；然而，线粒体功能障碍和紊乱的钙稳态已被牵连其中。我们先前已证明在亨廷顿舞蹈症细胞系和转基因小鼠中存在异常的线粒体钙处理。为了研究这些异常是否可能部分源于突变型亨廷顿蛋白中扩展的多聚谷氨酰胺序列的直接影响，我们将正常大鼠肝脏和人淋巴母细胞线粒体暴露于含有0、19或62个残基的多聚谷氨酰胺序列的谷胱甘肽S - 转移酶融合蛋白中。与牛血清白蛋白类似，每种蛋白构建体均非特异性地抑制琥珀酸支持的呼吸作用，且与多聚谷氨酰胺序列长度无关。仅在存在病理长度的多聚谷氨酰胺序列时，线粒体膜电位（状态4）有小幅但显著的降低。随着逐次添加少量Ca(2+)，暴露于病理长度多聚谷氨酰胺序列（约5 microM）的线粒体比暴露于其他蛋白构建体的线粒体更早且更大程度地去极化。这些结果表明，在亨廷顿舞蹈症细胞系和转基因小鼠中观察到的线粒体钙处理缺陷可能部分归因于突变型亨廷顿蛋白对线粒体的直接有害影响。
