Candia Robert F, Cohen Leah S, Morozova Viktoriya, Corbo Christopher, Alonso Alejandra D
Department of Biology, Center for Developmental Neuroscience, College of Staten Island, The City University of New York, Staten Island, NY, United States.
Biology Program, The Graduate Center, The City University of New York, New York, NY, United States.
Front Mol Neurosci. 2022 May 3;15:888420. doi: 10.3389/fnmol.2022.888420. eCollection 2022.
Tau is a cytosolic protein that has also been observed in the nucleus, where it has multiple proposed functions that are regulated by phosphorylation. However, the mechanism underlying the nuclear import of tau is unclear, as is the contribution of nuclear tau to the pathology of tauopathies. We have previously generated a pathological form of tau, PH-tau (pseudophosphorylation mutants S199E, T212E, T231E, and S262E) that mimics AD pathological behavior in cells, , and a mouse model. Here, we demonstrated that PH-tau translocates into the nucleus of transiently transfected HEK-293 cells, but wildtype tau does not. We identified a putative importin binding site in the tau sequence, and showed that disruption of this site prevents tau from entering the nucleus. We further showed that this nuclear translocation is prevented by inhibitors of both importin-α and importin-β. In addition, expression of PH-tau resulted in an enlarged population of dying cells, which is prevented by blocking its entry into the nucleus. PH-tau-expressing cells also exhibited disruption of the nuclear lamina and mislocalization of TDP-43 to the cytoplasm. We found that PH-tau does not bundle microtubules, and this effect is independent of nuclear translocation. These results demonstrate that tau translocates into the nucleus through the importin-α/β pathway, and that PH-tau exhibits toxicity after its nuclear translocation. We propose a model where hyperphosphorylated tau not only disrupts the microtubule network, but also translocates into the nucleus and interferes with cellular functions, such as nucleocytoplasmic transport, inducing mislocalization of proteins like TDP-43 and, ultimately, cell death.
tau是一种胞质蛋白，在细胞核中也有发现，其在细胞核中具有多种由磷酸化调节的假定功能。然而，tau核输入的潜在机制尚不清楚，核tau对tau蛋白病病理学的贡献也不清楚。我们之前生成了一种病理性tau形式，即PH-tau（假磷酸化突变体S199E、T212E、T231E和S262E），它在细胞和小鼠模型中模拟了AD的病理行为。在这里，我们证明了PH-tau可转运至瞬时转染的HEK-293细胞的细胞核中，但野生型tau则不能。我们在tau序列中鉴定出一个假定的输入蛋白结合位点，并表明该位点的破坏会阻止tau进入细胞核。我们进一步表明，输入蛋白-α和输入蛋白-β的抑制剂均可阻止这种核转运。此外，PH-tau的表达导致死亡细胞数量增加，而通过阻止其进入细胞核可防止这种情况发生。表达PH-tau的细胞还表现出核纤层的破坏以及TDP-43向细胞质的错误定位。我们发现PH-tau不会使微管成束，且这种作用与核转运无关。这些结果表明，tau通过输入蛋白-α/β途径转运至细胞核，并且PH-tau在核转运后表现出毒性。我们提出了一个模型，其中过度磷酸化的tau不仅破坏微管网络，还转运至细胞核并干扰细胞功能，如核质运输，导致TDP-43等蛋白质错误定位，并最终导致细胞死亡。
