Mutant huntingtin (mHtt) proteins interact to form aggregates, disrupting cellular functions including transcriptional dysregulation and iron imbalance in patients with Huntington’s disease (HD) and mouse disease models. Previous studies have indicated that mHtt may lead to abnormal iron homeostasis by upregulating the expression of iron response protein 1 (IRP1) in the striatum and cortex of N171-82Q HD transgenic mice, as well as in HEK293 cells expressing the N-terminal fragment of mHtt containing 160 CAG repeats. However, the mechanism underlying the upregulation of IRP1 remains unclear. We investigated the levels and phosphorylation status of signal transducer and activator of transcription 5 (STAT5) in the brains of N171-82Q HD transgenic mice using immunohistochemistry staining. We also assessed the nuclear localization of STAT5 protein through western blot and immunofluorescence, and measured the relative RNA expression levels of STAT5 and IRP1 using RT-PCR in both N171-82Q HD transgenic mice and HEK293 cells expressing the N-terminal fragment of huntingtin. Our findings demonstrate that the transcription factor STAT5 regulates the transcription of the IPR1 gene in HEK293 cells. Notably, both the brains of N171-82Q mice and 160Q HEK293 cells exhibited increased nuclear content of STAT5, despite unchanged total STAT5 expression. These results suggest that mHtt promotes the nuclear translocation of STAT5, leading to enhanced expression of IRP1. The nuclear translocation of STAT5 initiates abnormal iron homeostatic pathways, characterized by elevated IRP1 expression, increased levels of transferrin and transferrin receptor, and iron accumulation in the brains of HD mice. These findings provide valuable insights into potential therapeutic strategies targeting iron homeostasis in HD.

突变亨廷顿蛋白 (mHtt) 相互作用形成聚集体，破坏亨廷顿病 (HD) 患者和小鼠疾病模型中的细胞功能，包括转录失调和铁失衡。先前的研究表明，mHtt 可能通过上调 N171-82Q HD 转基因小鼠纹状体和皮层以及表达 N 末端片段的 HEK293 细胞中铁反应蛋白 1 (IRP1) 的表达，导致铁稳态异常。 mHtt 包含 160 个 CAG 重复序列。然而，IRP1 上调的机制仍不清楚。我们使用免疫组织化学染色研究了 N171-82Q HD 转基因小鼠大脑中信号转导子和转录激活子 5 (STAT5) 的水平和磷酸化状态。我们还通过蛋白质印迹和免疫荧光评估了STAT5蛋白的核定位，并使用 RT-PCR 测量了表达亨廷顿蛋白 N 末端片段的 N171-82Q HD 转基因小鼠和 HEK293 细胞中 STAT5和IRP1的相对 RNA 表达水平。我们的研究结果表明转录因子 STAT5 调节 HEK293 细胞中IPR1基因的转录。值得注意的是，尽管 STAT5 总表达没有变化，但 N171-82Q 小鼠和 160Q HEK293 细胞的大脑均表现出 STAT5 核含量增加。这些结果表明 mHtt 促进 STAT5 的核转位，导致 IRP1 表达增强。STAT5 的核易位启动了异常的铁稳态途径，其特征是 IRP1 表达升高、转铁蛋白和转铁蛋白受体水平增加以及 HD 小鼠大脑中铁的积累。这些发现为针对 HD 铁稳态的潜在治疗策略提供了宝贵的见解。