Cleavage at the 586 amino acid caspase-6 site in mutant huntingtin influences caspase-6 activation in vivo.
Cleavage at the 586 amino acid caspase-6 site in mutant huntingtin influences caspase-6 activation in vivo.
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DOI：
10.1523/jneurosci.2071-10.2010
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发表时间：
2010-11-10
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影响因子：
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通讯作者：
Hayden MR
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文献类型：
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作者：
Graham RK;Deng Y;Carroll J;Vaid K;Cowan C;Pouladi MA;Metzler M;Bissada N;Wang L;Faull RL;Gray M;Yang XW;Raymond LA;Hayden MR
亨廷顿病(HD)患者脑内半胱氨酸天冬氨酸氨基转移酶(Htp)裂解和核内hTt积聚是早期神经病变的表现。然而，hTt的caspase裂解与caspase激活模式在HD发病机制中的关系尚不清楚。YAC小鼠缺乏表达caspase-6抗性(C6R)突变体HTT(MHTT)的表型，突出了586aa caspase-6(Casp6)位点HTT的蛋白分解是HD病理中的关键机制。本研究的目的是探讨hTT基因第586位残基的蛋白降解在HD发病机制中的作用，并确定抑制mHTT的casp6裂解是否会改变体内的细胞死亡途径。在这里，我们证明，在人类和小鼠HD脑中，casp6而不是caspase-3的激活是在运动异常开始之前观察到的。Casp6活性水平与CAG大小直接相关，与发病年龄呈负相关。相反，C6R mHTT在体内的表达减弱了caspase的激活。在NMDA应用后，表达caspase可切割的原代纹状体神经元的casp6活性增加和细胞凋亡明显，但不表达C6R，mHTT。用casp6抑制剂预处理可以挽救这一范例中观察到的凋亡细胞死亡。这些数据表明，casp6的激活是HD疾病的早期标志。此外，这些数据提供了兴奋毒性通路和蛋白降解之间的明确联系，并表明C6R mHTT通过影响HD中神经细胞死亡和兴奋毒性通路的激活来保护神经退行性变。
Caspase cleavage of huntingtin (htt) and nuclear htt accumulation represent early neuropathological changes in brains of patients with Huntington disease (HD). However the relationship between caspase cleavage of htt and caspase activation patterns in the pathogenesis of HD remains poorly understood. The lack of a phenotype in YAC mice expressing caspase-6-resistant (C6R) mutant htt (mhtt) highlights proteolysis of htt at the 586aa caspase-6 (casp6) site as a key mechanism in the pathology of HD. The goal of this study was to investigate how proteolysis of htt at residue 586 plays a role in the pathogenesis of HD and determine whether inhibiting casp6 cleavage of mhtt alters cell death pathways in vivo. Here we demonstrate that activation of casp6, and not caspase-3, is observed before onset of motor abnormalities in human and murine HD brain. Active casp6 levels correlate directly with CAG size and inversely with age of onset. In contrast, in vivo expression of C6R mhtt attenuates caspase activation. Increased casp6 activity and apoptotic cell death is evident in primary striatal neurons expressing caspase-cleavable, but not C6R, mhtt following NMDA application. Pretreatment with a casp6 inhibitor rescues the apoptotic cell death observed in this paradigm. These data demonstrate that activation of casp6 is an early marker of disease in HD. Furthermore, these data provide a clear link between excitotoxic pathways and proteolysis and suggest that C6R mhtt protects against neurodegeneration by influencing the activation of neuronal cell death and excitotoxic pathways operative in HD.