CHIP and HSPs interact with β-APP in a proteasome-dependent manner and influence Aβ metabolism
CHIP and HSPs interact with β-APP in a proteasome-dependent manner and influence Aβ metabolism
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DOI：
10.1093/hmg/ddm030
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发表时间：
2007-04-01
影响因子：
3.5
通讯作者：
Querfurth, Henry W.
中科院分区：
文献类型：
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作者：
Kumar, Pravir;Ambasta, Rashmi K.;Querfurth, Henry W.
c端Hsp70相互作用蛋白（CHIP）具有共同伴侣和泛素连接酶的双重功能。CHIP在多聚谷氨酰胺扩张障碍、帕金森氏病和阿尔茨海默病的tau蛋白生物学中的作用越来越大。我们研究了CHIP参与β -淀粉样蛋白前体蛋白及其衍生物β -淀粉样蛋白（A β）的代谢。通过免疫沉淀、荧光定位和交联等方法，内源性CHIP和β APP在大脑和培养的骨骼肌管中相互作用，并在稳定的HEK细胞系中表达。它们的相互作用仅限于高尔基体和内质室。在含有MG132的蛋白酶体抑制剂存在下，内源性和表达的β APP水平显著升高，与CHIP的相互作用增强。同时，在测试的各种热休克蛋白（HSPs）中，蛋白酶体抑制最一致地诱导了Hsp70水平。因此，CHIP、Hsp70和holo-beta APP配合物（以及c端片段）在MG132的作用下得到稳定。此外，CHIP本身被证明既可以增加细胞全β APP水平，又可以保护细胞免受氧化应激和降解。有趣的是，CHIP还促进泛素与β - APP的关联，这意味着较小的β - APP池注定要进行蛋白酶体加工。在神经元培养中，CHIP和Hsp70/90的表达降低了稳态细胞A β水平，并加速了其在脉冲追逐实验中的降解。CHIP和HSP相互作用的功能意义，特别是与Hsp70的相互作用，使用siRNA和神经细胞进行了测试，其中显示出对A β诱导毒性的保护。我们得出结论，CHIP作为一种双分子开关，一方面与HSP相互作用以稳定正常的全β APP，另一方面也有助于β APP分子亚群的泛素化，这些分子注定要被蛋白酶体降解。CHIP还以与其已知的神经保护特性一致的方式加速A β的清除。
The C-terminus Hsp70 interacting protein (CHIP) has dual function as both co-chaperone and ubiquitin ligase. CHIP is increasingly implicated in the biology of polyglutamine expansion disorders, Parkinson's disease and tau protein in Alzheimer's disease. We investigated the involvement of CHIP in the metabolism of the beta-amyloid precursor protein and its derivative beta-amyloid (A beta). Using immunoprecipitation, fluorescence localization and crosslinking methods, endogenous CHIP and beta APP interact in brain and cultured skeletal myotubes as well as when they are expressed in stable HEK cell lines. Their interaction is confined to Golgi and ER compartments. In the presence of the proteasome inhibitor with MG132, endogenous and expressed beta APP levels are significantly increased and accordingly, the interaction with CHIP enhanced. Concurrently, levels of Hsp70 were most consistently induced by proteasome inhibition among the various heat shock proteins (HSPs) tested. Thus, complexes of CHIP, Hsp70 and holo-beta APP (as well as C-terminal fragments) were stabilized by the action of MG132. Moreover, CHIP itself is shown to both increase cellular holo-beta APP levels and protect it from oxidative stress and degradation. Interestingly, CHIP also promotes the association of ubiquitin with beta APP, implying that a smaller pool of beta APP is destined for proteasomal processing. In neuronal cultures, CHIP and Hsp70/90 expression reduce steady-state cellular A beta levels and hasten its degradation in pulse-chase experiments. The functional significance of CHIP and HSP interactions, especially with Hsp70, was tested using siRNA and in neuronal cells where protection from A beta-induced toxicity is shown. We conclude that CHIP, as a bimolecular switch, interacts with HSP to stabilize normal holo-beta APP on the one hand while also assisting in the ubiquitination of a subpopulation of beta APP molecules that are destined for proteasome degradation. CHIP also hastens the clearance of A beta in a manner consistent with its known neuroprotective properties.