Effect of overexpression of cathepsin E and Bcl-2 on neuronal death

近年来，在不同的神经病理条件下，细胞内蛋白分解系统的改变引起了人们的关注，在本研究中，我们确定了与组织蛋白酶E相关的蛋白分解事件与各种神经元变性过程的关系。首先，研究了组织蛋白酶E在大鼠大脑皮层和脑干的表达和定位随年龄的变化。这种酶在胚胎阶段的这些组织中几乎检测不到，而随着出生后年龄的增长，它在这些组织中的表达越来越多。在含脂褐素的老年神经元溶酶体中，组织蛋白酶E与溶酶体天冬氨酸蛋白酶E共定位。结果表明，衰老导致组织蛋白酶E在神经元中的表达和定位增加，并导致内体/溶酶体蛋白分解系统的改变，这可能与脂褐质的形成有关。第二，组织蛋白酶B被证明是…在各种脑细胞类型中，更多的是小胶质细胞，这种酶主要作为成熟酶存在于内体中。第三，在神经元特异烯醇化酶调控下，我们检测了在成年转基因小鼠中，在缺氧缺血诱导的选择性神经元死亡中，Bcl-2过表达对海马CA1区神经元和齿状颗粒细胞的影响。结果表明，Bcl2的过表达有效地抑制了齿状回颗粒细胞的凋亡，但仅延缓了CA1区神经元的死亡，提示CA1区存在非凋亡性、caspase非依赖性的神经元死亡机制。第四，当被激活的小胶质细胞处理时，神经元性PC12细胞发生凋亡，伴随着caspase-3样蛋白酶的激活和DNA片段化。用类似caspase-3的蛋白水解酶抑制剂对神经细胞进行预处理并不能逆转这种细胞死亡。Bcl2过表达也不能抑制激活的小胶质细胞诱导的神经元死亡。本研究通过阻断caspase-3蛋白酶级联反应，为激活的小胶质细胞诱导的神经元死亡提供了另一种死亡途径。较少

In past years attention has been paid to the altered intracellular proteolytic system in relation to different neuropathological conditions, In this study, we have determined the association of the proteolytic events relating to cathepsin E, a non-lysosomal aspartic proteinase, with various neuronal degeneration process. First, age-related changes in the expression and localization of cathepsin E was determined in the rat cerebral cortex and the brainstem. The enzyme was barely detectable in these tissues in the embryonic stages, whereas it was increasingly expressed in these tissues with aging after birth. cathepsin E was colocalized with the lysosomal aspartic proteinase cathepsin E in the lipofuscin-containing lysosomes in the aged neurons. The results indicate that aging results in the increased expression and localization of cathepsin E in neurons and changes in the endosomal/lysosomal proteolytic system, which may be related to lipofucigenesis. Second, cathepsin B was shown to be … More the most abundant in microglia among various brain cell types, where the enzyme existed predominantly as the mature enzyme in the endosome. Third, we have examined effects of Bcl-2 overexpression on selective neuronal death of the hippocampal CA1 neurons and the dentate granule cells induced by hypoxic-ischemia in adult transgenic mice overexpressing human Bcl-2 under the control of neuron-specific enolase. The results indicate that the overexpression of Bcl-2 effectively suppressed dentate granule cell apoptosis but only delayed cell death of the CA1 neurons, suggesting the occurrence of non-apoptiotic, caspase-independent mechanism for neuronal death in the CA1 subfield. Fourth, when treated with activated microglia, neuronal PC12 cells undergo apoptosis accompanied by caspase-3-like protease activation and DNA fragmentation. Pretreatment of the neuronal cells with caspase-3-like protease inhibitors did not reverse this cell death. Bcl-2 overexpression also could not suppress the activated microglia-induced neuronal death. this study provides an alternative death pathway for activated microglia- induced neuronal death by blockage of the caspase-3 protease cascade. Less