HAP40 is a conserved central regulator of Huntingtin and a potential modulator of Huntington's disease pathogenesis.
HAP40 is a conserved central regulator of Huntingtin and a potential modulator of Huntington's disease pathogenesis.
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HAP40是一个保守的亨廷顿蛋白中枢调节因子，也是亨廷顿病发病机制的潜在调节因子。
DOI：
10.1371/journal.pgen.1010302
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发表时间：
2022-07
期刊：
影响因子：
4.5
通讯作者：
中科院分区：
文献类型：
--
作者：
亨廷顿蛋白（HTT）生理功能紊乱是亨廷顿病（HD）的一个假定致病因素。然而，很少有人知道HTT是如何在体内调节。在蛋白质组学研究中，我们分离了一个新的~ 40 kDa蛋白作为果蝇HTT的强结合伴侣，并证明它是HAP 40的功能性直系同源物，HAP 40是最近显示的HTT相关蛋白，可调节HTT的构象，但其生理和病理作用尚不清楚。我们发现，在果蝇和人类细胞中，HAP 40与HTT保持保守的物理和功能相互作用。此外，HAP 40的缺失导致与HTT敲除相似的表型。更引人注目的是，HAP 40强烈影响HTT的稳定性，因为HAP 40的耗尽显著降低了内源性HTT蛋白的水平，而HAP 40过表达显著延长了其半衰期。相反，在没有HTT的情况下，大部分HAP 40蛋白被降解，可能是通过蛋白酶体。此外，HTT和HAP 40之间的亲和力不受HTT中多聚谷氨酰胺扩增的显著影响，并且与早期报道相反，在来自小鼠HD模型或人类患者的HD细胞中没有内源性HAP 40蛋白的异常积累。最后，当在HD的果蝇模型中测试时，HAP 40部分地调节全长突变HTT诱导的神经变性，而对突变HTT外显子1片段的毒性没有明显影响。总之，我们的研究揭示了一个保守的机制，管理的稳定性和HTT的体内功能，并证明HAP 40是一个中央和积极的内源性HTT的调节。此外，我们的研究结果支持突变体HTT是有毒的，无论其伴侣HAP 40的存在，并暗示HAP 40作为HD发病机制的潜在调节剂，通过其对HTT的功能，稳定性和突变体HTT的毒性的效力的多重作用。亨廷顿蛋白（HTT）中的异常多聚谷氨酰胺扩增导致神经退行性亨廷顿病（HD）。鉴于HD的致病机制复杂且尚不清楚，人们对靶向HTT作为针对HD的治疗策略非常感兴趣。因此，了解HTT通常如何监管非常重要。在果蝇的蛋白质组学研究中，我们分离出一种新的蛋白质作为一个强有力的结合伙伴飞HTT同源物，并证明它是哺乳动物HAP 40，已知的蛋白质调节HTT的构象，但不清楚的生理和病理作用的功能对应物。我们发现HTT与HAP 40的物理和功能相互作用从苍蝇到人类细胞都是保守的，HAP 40对于HTT的正常功能和蛋白质稳定性是必不可少的，而在没有HTT的情况下，HAP 40通过蛋白酶体被快速清除。此外，HTT蛋白中的多聚谷氨酰胺扩增不影响其对HAP 40的亲和力或引起HD细胞中HAP 40的异常积累。最后，我们观察到HAP 40可以调节表达全长突变HTT的果蝇模型中的HD相关神经变性。总之，我们的研究表明HAP 40是HTT的高度保守且重要的调节因子，也是实现HD细胞特异性HTT降低的潜在候选者。
Perturbation of huntingtin (HTT)’s physiological function is one postulated pathogenic factor in Huntington’s disease (HD). However, little is known how HTT is regulated in vivo. In a proteomic study, we isolated a novel ~40kDa protein as a strong binding partner of Drosophila HTT and demonstrated it was the functional ortholog of HAP40, an HTT associated protein shown recently to modulate HTT’s conformation but with unclear physiological and pathologic roles. We showed that in both flies and human cells, HAP40 maintained conserved physical and functional interactions with HTT. Additionally, loss of HAP40 resulted in similar phenotypes as HTT knockout. More strikingly, HAP40 strongly affected HTT’s stability, as depletion of HAP40 significantly reduced the levels of endogenous HTT protein while HAP40 overexpression markedly extended its half-life. Conversely, in the absence of HTT, the majority of HAP40 protein were degraded, likely through the proteasome. Further, the affinity between HTT and HAP40 was not significantly affected by polyglutamine expansion in HTT, and contrary to an early report, there were no abnormal accumulations of endogenous HAP40 protein in HD cells from mouse HD models or human patients. Lastly, when tested in Drosophila models of HD, HAP40 partially modulated the neurodegeneration induced by full-length mutant HTT while showed no apparent effect on the toxicity of mutant HTT exon 1 fragment. Together, our study uncovers a conserved mechanism governing the stability and in vivo functions of HTT and demonstrates that HAP40 is a central and positive regulator of endogenous HTT. Further, our results support that mutant HTT is toxic regardless of the presence of its partner HAP40, and implicate HAP40 as a potential modulator of HD pathogenesis through its multiplex effect on HTT’s function, stability and the potency of mutant HTT’s toxicity. Abnormal polyglutamine expansion in huntingtin (HTT) protein causes neurodegenerative Huntington’s disease (HD). Given the complex and still unclear pathogenic mechanisms underlying HD, there is great interest in targeting HTT as a therapeutic strategy against HD. Accordingly, it is important to understand how HTT is normally regulated. In a proteomic study in Drosophila, we isolated a novel protein as a strong binding partner of fly HTT homolog and demonstrated that it was the functional counterpart of mammalian HAP40, a protein known to modulate HTT’s conformation but with unclear physiological and pathologic roles. We found that the physical and functional interactions of HTT with HAP40 were conserved from flies to human cells, and HAP40 was essential for HTT’s normal functions and protein stability, while in the absence of HTT, HAP40 was quickly cleared through the proteasome. Further, polyglutamine expansion in HTT protein did not affect its affinity for HAP40 or cause abnormal accumulation of HAP40 in HD cells. Lastly, we observed that HAP40 could modulate HD-associated neurodegeneration in fly models that expressed full-length mutant HTT. Together, our study demonstrates that HAP40 is a highly conserved and essential regulator of HTT and a potential candidate for achieving specific HTT-lowering in HD cells.
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影响因子：
64.8
作者：
Guo Q;Bin Huang;Cheng J;Seefelder M;Engler T;Pfeifer G;Oeckl P;Otto M;Moser F;Maurer M;Pautsch A;Baumeister W;Fernández-Busnadiego R;Kochanek S
通讯作者：
Kochanek S
影响因子：
--
作者：
Nie J;Mahato S;Zelhof AC
通讯作者：
Zelhof AC
DOI：
10.1073/pnas.92.19.8710
发表时间：
1995-09-12
影响因子：
11.1
作者：
GUTEKUNST, CA;LEVEY, AI;HERSCH, SM
通讯作者：
HERSCH, SM
影响因子：
3.8
作者：
Ko, J;Ou, S;Patterson, PH
通讯作者：
Patterson, PH
影响因子：
16.2
作者：
ARONIN, N;CHASE, K;DIFIGLIA, M
通讯作者：
DIFIGLIA, M