Rhine Kevin, Epstein Elle, Carlson Natasha M, Ge Xuezhen, Mizrahi Orel, Kamat Anika, Hermann Anita, Brothers William R, Ravits John, Bennett Eric J, Pekkurnaz Gülçin, Yeo Gene W
Department of Cellular & Molecular Medicine, University of California, San Diego, La Jolla, CA 92037, USA.
Sanford Stem Cell Institute Innovation Center and Sanford Consortium for Regenerative Medicine, University of California, San Diego, La Jolla, CA 92037, USA.
bioRxiv. 2025 Aug 5:2025.08.04.668575. doi: 10.1101/2025.08.04.668575.
Neurodegenerative diseases are linked with dysregulation of the integrated stress response (ISR), which coordinates cellular homeostasis during and after stress events. Cellular stress can arise from several sources, but there is significant disagreement about which stress might contribute to aging and neurodegeneration. Here, we leverage directed transdifferentiation of human fibroblasts into aged neurons to determine the source of ISR activation. We demonstrate that increased accumulation of cytoplasmic double-stranded RNA (dsRNA) activates the eIF2α kinase PKR, which in turn triggers the ISR in aged neurons and leads to sequestration of dsRNA in stress granules. Aged neurons accumulate endogenous mitochondria-derived dsRNA that directly binds to PKR. This mitochondrial dsRNA leaks through damaged mitochondrial membranes and forms cytoplasmic foci in aged neurons. Finally, we demonstrate that PKR inhibition leads to the cessation of stress, resumption of cellular translation, and restoration of RNA-binding protein expression. Together, our results identify a source of RNA stress that destabilizes aged neurons and may contribute to neurodegeneration.
神经退行性疾病与综合应激反应（ISR）失调有关，ISR在应激事件期间及之后协调细胞内稳态。细胞应激可源于多种因素，但对于哪种应激可能导致衰老和神经退行性变存在重大分歧。在此，我们利用人成纤维细胞向衰老神经元的定向转分化来确定ISR激活的来源。我们证明，细胞质双链RNA（dsRNA）积累增加会激活eIF2α激酶PKR，进而在衰老神经元中触发ISR，并导致dsRNA在应激颗粒中隔离。衰老神经元积累内源性线粒体衍生的dsRNA，其直接与PKR结合。这种线粒体dsRNA通过受损的线粒体膜泄漏，并在衰老神经元中形成细胞质病灶。最后，我们证明PKR抑制导致应激停止、细胞翻译恢复以及RNA结合蛋白表达恢复。总之，我们的结果确定了一种RNA应激源，它会使衰老神经元不稳定，并可能导致神经退行性变。
