Proteasome Inhibition in Brain Aging

蛋白酶体存在于大脑的所有细胞中，并参与大部分蛋白质的降解。特别是，蛋白酶体负责调节大脑中大多数被氧化和受损的蛋白质的降解。蛋白酶体由多个亚基组成，通过至少3个不同的蛋白水解酶活性的协同作用来降解蛋白质。最近我们发现，在正常的脑老化过程中，蛋白酶体的胰凝乳酶样活性存在脑区特异性损伤。我们实验室最近的研究表明，热休克蛋白(HSP)的表达减少和蛋白酶体亚单位的表达减少可能是年龄相关性蛋白酶体抑制发生的可能机制。这项建议中的数据清楚地表明，抑制蛋白酶体活性足以诱导氧化DNA在大脑中的积累，尽管蛋白酶体抑制在介导大脑中与年龄相关的氧化应激增加中的可能作用尚未被确定。这一建议的重点是检验一种假设，即大脑中HSP、HSP相关蛋白和个别蛋白酶体亚单位的表达减少直接导致蛋白酶体活性的年龄相关性损害，而蛋白酶体活性的下降直接导致蛋白质氧化和DNA氧化的年龄相关性增加。验证这一假说的具体目的如下：1)确定衰老脑中蛋白酶体表达的变化2)确定衰老脑中所有蛋白酶体蛋白分解活性的变化3)确定HSP及其相关蛋白在衰老脑中表达的变化4)确定蛋白酶体活性在衰老脑中被抑制的机制5)阐明蛋白酶体抑制在与衰老相关的蛋白质氧化和DNA氧化增加中的作用。总之，这些研究将为了解大脑中的蛋白酶体生物学提供基础，并阐明蛋白酶体抑制作为与大脑老化相关的有害影响的一个因素。

The proteasome is found in all cells of the brain, and mediates the majority of overall protein degradation. In particular, the proteasome is responsible for mediating the degradation of most oxidized and damaged proteins in the brain. The proteasome is composed of multiple subunits, and degrades proteins through the coordinated efforts of at least 3 distinct proteolytic activities. Recently we have identified that there is a brain region specific impairment in the chymotrypsin-like activity of the proteasome, during normal brain aging. Recent studies from our laboratory indicate a possible role for decreased expression of heat shock proteins (HSP), and decreased expression of proteasome subunits, as a possible mechanism by which age-related proteasome inhibition occurs. Data in this proposal clearly demonstrate that inhibition of proteasome activity is sufficient to induce the accumulation of oxidized DNA in the brain, although the possible role of proteasome inhibition in mediating age-related increases in oxidative stress in the brain has not been determined previously. The focus of this proposal is to test the hypothesis that decreased expression of HSP, HSP associated proteins, and individual proteasome subunits in the brain directly contribute to age-related impairment of proteasome activity, which directly contributes to age-related increases in protein oxidation and DNA oxidation. The specific aims for testing this hypothesis are as follows: 1) To determine alterations in proteasome expression in the aging brain 2) To determine alterations in all proteasome proteolytic activities in the aging brain 3) To determine alterations in the expression of HSP, and HSP associated proteins, in the aging brain 4) To determine the mechanism by which proteasome activity is inhibited in the aging brain 5) To elucidate the role of proteasome inhibition in age-related increases in protein oxidation and DNA oxidation. Together, these studies will provide a basis for understanding proteasome biology in the brain, and elucidate the involvement of proteasome inhibition as a contributor to the deleterious effects associated with brain aging.