Laboratory of Molecular Neurobiology, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Republic of Korea.
Integrated Institute of Biomedical Research, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Republic of Korea.
J Neurosci. 2021 Jun 16;41(24):5138-5156. doi: 10.1523/JNEUROSCI.2494-20.2021. Epub 2021 May 10.
Protein aggregation can induce explicit neurotoxic events that trigger a number of presently untreatable neurodegenerative disorders. Chaperones, on the other hand, play a neuroprotective role because of their ability to unfold and refold abnormal proteins. The progressive nature of neurotoxic events makes it important to discover endogenous factors that affect pathologic and molecular phenotypes of neurodegeneration in animal models. Here, we identified microtubule-associated protein tau, and chaperones Hsp70 (heat shock protein 70) and DNAJA1 (DJ2) as endogenous substrates of cereblon (CRBN), a substrate-recruiting subunit of cullin4-RING-E3-ligase. This recruitment results in ubiquitin-mediated degradation of tau, Hsp70, and DJ2. Knocking out CRBN enhances the chaperone activity of DJ2, resulting in decreased phosphorylation and aggregation of tau, improved association of tau with microtubules, and reduced accumulation of pathologic tau across brain. Functionally abundant DJ2 could prevent tau aggregation induced by various factors like okadaic acid and heparin. Depletion of CRBN also decreases the activity of tau-kinases including GSK3α/β, ERK, and p38. Intriguingly, we found a high expression of CRBN and low levels of DJ2 in neuronal tissues of 5XFAD and APP knock-in male mouse models of Alzheimer's disease. This implies that CRBN-mediated DJ2/Hsp70 pathway may be compromised in neurodegeneration. Being one of the primary pathogenic events, elevated CRBN can be a contributing factor for tauopathies. Our data provide a functional link between CRBN and DJ2/Hsp70 chaperone machinery in abolishing the cytotoxicity of aggregation-prone tau and suggest that mice serve as an animal model of resistance against tauopathies for further exploration of the molecular mechanisms of neurodegeneration.
蛋白质聚集会导致明确的神经毒性事件，从而引发许多目前无法治疗的神经退行性疾病。另一方面，伴侣蛋白由于能够展开和重折叠异常蛋白，因此发挥神经保护作用。神经毒性事件的进行性特征使得发现影响动物模型中神经退行性病变的病理和分子表型的内源性因素变得尤为重要。在这里，我们鉴定微管相关蛋白 tau 以及伴侣蛋白 Hsp70（热休克蛋白 70）和 DNAJA1（DJ2）为 cereblon（CRBN）的内源性底物，CRBN 是 cullin4-RING-E3 连接酶的底物募集亚基。这种募集导致 tau、Hsp70 和 DJ2 的泛素化介导降解。敲除 CRBN 增强了 DJ2 的伴侣蛋白活性，导致 tau 的磷酸化和聚集减少，tau 与微管的结合增加，以及病理性 tau 在大脑中的积累减少。功能丰富的 DJ2 可以防止各种因素（如 okadaic 酸和肝素）诱导的 tau 聚集。CRBN 的耗竭还降低了包括 GSK3α/β、ERK 和 p38 在内的 tau 激酶的活性。有趣的是，我们在阿尔茨海默病的 5XFAD 和 APP 敲入雄性小鼠模型的神经元组织中发现了高表达的 CRBN 和低水平的 DJ2。这意味着 CRBN 介导的 DJ2/Hsp70 途径可能在神经退行性变中受到损害。作为主要的致病事件之一，CRBN 升高可能是 tau 病的一个促成因素。我们的数据提供了 CRBN 和 DJ2/Hsp70 伴侣蛋白机制之间在消除聚集倾向 tau 的细胞毒性方面的功能联系，并表明该小鼠模型可能是抵抗 tau 病的动物模型，用于进一步探索神经退行性病变的分子机制。
