Calpain-mediated ataxin-3 cleavage in the molecular pathogenesis of spinocerebellar ataxia type 3 (SCA3)
Calpain-mediated ataxin-3 cleavage in the molecular pathogenesis of spinocerebellar ataxia type 3 (SCA3)
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DOI：
10.1093/hmg/dds449
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发表时间：
2013-02-01
影响因子：
3.5
通讯作者：
Huu Phuc Nguyen
中科院分区：
文献类型：
--
作者：
Huebener, Jeannette;Weber, Jonasz Jeremiasz;Huu Phuc Nguyen
脊髓小脑性共济失调3型（SCA 3）的病理特征是在一种特定的神经元亚型中形成核内聚集体，其中含有共济失调蛋白3（SCA 3中的突变蛋白）。已经提出共济失调蛋白-3被蛋白水解酶，特别是被钙蛋白酶和半胱天冬酶切割，最终导致聚集体的形成。在我们的研究中，我们研究了钙激活酶在体外和体内切割共济失调蛋白-3的能力。我们在细胞培养物和小鼠脑匀浆中证明，钙蛋白酶，特别是钙蛋白酶-2对过表达的共济失调蛋白-3的裂解发生，并且多聚谷氨酰胺扩增的共济失调蛋白-3对钙蛋白酶降解更敏感。基于这些结果，我们研究了钙蛋白酶对SCA 3在体内发病机制的影响。为此，我们通过敲除内源性钙蛋白酶抑制剂钙蛋白酶抑制素来增强SCA 3转基因小鼠模型中的钙蛋白酶活性。双突变小鼠表现出神经系统表型恶化，小脑核聚集体数量增加，神经退行性变加速。这项研究证实了钙依赖性钙蛋白酶型蛋白酶在SCA 3发病机制中的重要性，并表明对共济失调蛋白-3裂解途径的操纵和对细胞内钙稳态的调节可能代表SCA 3治疗干预的新靶点。
Spinocerebellar ataxia type 3 (SCA3) is pathologically characterized by the formation of intranuclear aggregates which contain ataxin-3, the mutated protein in SCA3, in a specific subtype of neurons. It has been proposed that ataxin-3 is cleaved by proteolytic enzymes, in particular by calpains and caspases, eventually leading to the formation of aggregates. In our study, we examined the ability of calpains to cleave ataxin-3 in vitro and in vivo. We demonstrated in cell culture and mouse brain homogenates that cleavage of overexpressed ataxin-3 by calpains and in particular by calpain-2 occur and that polyglutamine expanded ataxin-3 is more sensitive to calpain degradation. Based on these results, we investigated the influence of calpains on the pathogenesis of SCA3 in vivo. For this purpose, we enhanced calpain activity in a SCA3 transgenic mouse model by knocking out the endogenous calpain inhibitor calpastatin. Double-mutant mice demonstrated an aggravated neurological phenotype with an increased number of nuclear aggregates and accelerated neurodegeneration in the cerebellum. This study confirms the critical importance of calcium-dependent calpain-type proteases in the pathogenesis of SCA3 and suggests that the manipulation of the ataxin-3 cleavage pathway and the regulation of intracellular calcium homeostasis may represent novel targets for therapeutic intervention in SCA3.