Frontotemporal Lobar Dementia Mutant Tau Impairs Axonal Transport through a Protein Phosphatase 1γ-Dependent Mechanism.
Frontotemporal Lobar Dementia Mutant Tau Impairs Axonal Transport through a Protein Phosphatase 1γ-Dependent Mechanism.
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DOI：
10.1523/jneurosci.1914-20.2021
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发表时间：
2021-11-10
期刊：
影响因子：
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通讯作者：
Kanaan NM
中科院分区：
文献类型：
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作者：
Combs B;Christensen KR;Richards C;Kneynsberg A;Mueller RL;Morris SL;Morfini GA;Brady ST;Kanaan NM
病理性 tau 蛋白修饰是阿尔茨海默病和相关痴呆症的特征，但 tau 蛋白毒性机制仍存在争议。 tau 的遗传性突变会导致早发性额颞叶痴呆 (FTLD-tau)，并且通常用于模拟 tau 病中 tau 毒性的机制。先前在分离鱿鱼轴浆模型中的研究表明，tau 蛋白的几种致病形式通过涉及蛋白磷酸酶 1 (PP1) 激活的机制抑制轴突运输。在这里，我们确定 P301L 和 R5L FTLD 突变 tau 蛋白作为单体蛋白对轴突运输产生毒性作用。我们评估了野生型或突变型 tau 与特定 PP1 同工型（α、β 和 γ）的相互作用，以使用来自两性的原代大鼠海马神经元来研究这种相互作用如何导致这种毒性作用。下拉和生物发光共振能量转移实验揭示了野生型 tau 与 PP1α 和 PP1γ 亚型的选择性相互作用，但与 PP1β 没有选择性相互作用，P301L tau 突变显着增加了 PP1β 的相互作用。邻近连接测定的结果证实了原代海马神经元中的相互作用。此外，这些神经元中 FTLD 连接突变 tau 的表达增强了活性 PP1 的水平，也增加了荧光标记囊泡在顺行和逆行方向上的暂停频率。敲除 PP1γ（而非 PP1α）可以挽救 P301L 和 R5L tau 的货物暂停效应，这一结果通过删除 P301L tau 氨基末端的磷酸酶激活结构域得到复制。这些发现支持了一种 tau 毒性模型，该模型涉及特定 PP1γ 依赖性途径的异常激活，该途径会破坏神经元中的轴突运输。意义声明 Tau 病理学与阿尔茨海默病和其他 tau 病中的神经变性密切相关，但毒性机制仍然是一个有争议的话题。我们之前提出，病理性 tau 蛋白形式通过异常激活破坏轴突运输的 PP1 依赖性途径来诱导功能障碍和退化。在这里，我们证明 tau 直接与特定的 PP1 同工型相互作用，增加活性 PP1 的水平。致病性 tau 突变增强了这种相互作用，进一步增加了活性 PP1 水平并损害了离体鱿鱼轴浆和初级海马神经元的轴突运输。突变 tau 介导的轴突运输损伤是由 PP1γ 和位于 tau 氨基末端的磷酸酶激活结构域介导的。这项工作对于理解和潜在减轻 tau 蛋白病中 tau 蛋白介导的神经毒性具有重要意义。
Pathologic tau modifications are characteristic of Alzheimer's disease and related dementias, but mechanisms of tau toxicity continue to be debated. Inherited mutations in tau cause early onset frontotemporal lobar dementias (FTLD-tau) and are commonly used to model mechanisms of tau toxicity in tauopathies. Previous work in the isolated squid axoplasm model demonstrated that several pathogenic forms of tau inhibit axonal transport through a mechanism involving activation of protein phosphatase 1 (PP1). Here, we determined that P301L and R5L FTLD mutant tau proteins elicit a toxic effect on axonal transport as monomeric proteins. We evaluated interactions of wild-type or mutant tau with specific PP1 isoforms (α, β, and γ) to examine how the interaction contributes to this toxic effect using primary rat hippocampal neurons from both sexes. Pull-down and bioluminescence resonance energy transfer experiments revealed selective interactions of wild-type tau with PP1α and PP1γ isoforms, but not PP1β, which were significantly increased by the P301L tau mutation. The results from proximity ligation assays confirmed the interaction in primary hippocampal neurons. Moreover, expression of FTLD-linked mutant tau in these neurons enhanced levels of active PP1, also increasing the pausing frequency of fluorescently labeled vesicles in both anterograde and retrograde directions. Knockdown of PP1γ, but not PP1α, rescued the cargo-pausing effects of P301L and R5L tau, a result replicated by deleting a phosphatase-activating domain in the amino terminus of P301L tau. These findings support a model of tau toxicity involving aberrant activation of a specific PP1γ-dependent pathway that disrupts axonal transport in neurons. SIGNIFICANCE STATEMENT Tau pathology is closely associated with neurodegeneration in Alzheimer's disease and other tauopathies, but the toxic mechanisms remain a debated topic. We previously proposed that pathologic tau forms induce dysfunction and degeneration through aberrant activation of a PP1-dependent pathway that disrupts axonal transport. Here, we show that tau directly interacts with specific PP1 isoforms, increasing levels of active PP1. Pathogenic tau mutations enhance this interaction, further increasing active PP1 levels and impairing axonal transport in isolated squid axoplasm and primary hippocampal neurons. Mutant-tau-mediated impairment of axonal transport was mediated by PP1γ and a phosphatase-activating domain located at the amino terminus of tau. This work has important implications for understanding and potentially mitigating tau-mediated neurotoxicity in tauopathies.