Lysosomal proteolysis inhibition selectively disrupts axonal transport of degradative organelles and causes an Alzheimer's-like axonal dystrophy.
Lysosomal proteolysis inhibition selectively disrupts axonal transport of degradative organelles and causes an Alzheimer's-like axonal dystrophy.
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DOI：
10.1523/jneurosci.6412-10.2011
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发表时间：
2011-05-25
期刊：
影响因子：
--
通讯作者：
Nixon RA
中科院分区：
文献类型：
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作者：
Lee S;Sato Y;Nixon RA
在阿尔茨海默病（AD）标志性的神经突营养不良中，含有未完全消化蛋白质的自噬泡选择性地在局灶性轴突肿胀处积聚，反映了轴突运输和自噬两方面的缺陷。在此，我们研究了溶酶体蛋白水解受损可能是导致神经突营养不良的这两种缺陷的基础这一可能性。在表达荧光标记物的原代小鼠皮质活神经元中，轴突中形成的LC3阳性自噬体迅速获得内溶酶体标记物Rab7和LAMP1，并进行专一的逆行运动。这些被运输的自噬泡在与双向移动的溶酶体融合时开始进行蛋白水解清除，溶酶体在更近端的轴突水平和胞体处数量增多。通过直接抑制组织蛋白酶或抑制溶酶体酸化来破坏溶酶体蛋白水解，会减缓自溶酶体、晚期内体和溶酶体的轴突运输，并导致它们在营养不良的轴突肿胀处选择性积聚。在这些条件下，不含组织蛋白酶的线粒体和其他细胞器正常移动，表明轴突运输系统的整体功能得以保留。由溶酶体蛋白水解抑制诱导的营养不良性肿胀在成分上与几种AD小鼠模型中的相似，并且还获得了其他类似AD的特征，包括泛素、APP的免疫阳性以及神经丝蛋白过度磷酸化。溶酶体蛋白水解的恢复逆转了具有蛋白水解作用的Rab7囊泡的受影响运动，这反过来又在很大程度上清除了自噬底物并逆转了轴突营养不良。这些研究将神经元溶酶体蛋白水解中与AD相关的缺陷确定为与AD相关的选择性运输异常和神经突营养不良的高度特征性模式的一个可能基础。
In the hallmark neuritic dystrophy of Alzheimer’s disease (AD), autophagic vacuoles containing incompletely digested proteins selectively accumulate in focal axonal swellings, reflecting defects in both axonal transport and autophagy. Here, we investigated the possibility that impaired lysosomal proteolysis could be a basis for both defects leading to neuritic dystrophy. In living primary mouse cortical neurons expressing fluorescence-tagged markers, LC3-positive autophagosomes forming in axons rapidly acquired the endo-lysosomal markers, Rab7 and LAMP1, and underwent exclusive retrograde movement. Proteolytic clearance of these transported autophagic vacuoles was initiated upon fusion with bi-directionally moving lysosomes that increase in number at more proximal axon levels and in the perikaryon. Disrupting lysosomal proteolysis by either inhibiting cathepsins directly or by suppressing lysosomal acidification slowed the axonal transport of autolysosomes, late endosomes and lysosomes and caused their selective accumulation within dystrophic axonal swellings. Mitochondria and other organelles lacking cathepsins moved normally under these conditions, indicating that the general functioning of the axonal transport system was preserved. Dystrophic swellings induced by lysosomal proteolysis inhibition resembled in composition those in several mouse models of AD and also acquired other AD-like features, including immunopositivity for ubiquitin, APP, and neurofilament protein hyperphosphorylation. Restoration of lysosomal proteolysis reversed the affected movements of proteolytic Rab7 vesicles, which in turn, largely cleared autophagic substrates and reversed the axonal dystrophy. These studies identify the AD-associated defects in neuronal lysosomal proteolysis as a possible basis for the selective transport abnormalities and highly characteristic pattern of neuritic dystrophy associated with AD.