Understanding the pathogenic mechanisms of disease mutations is critical to advancing treatments. ALS-associated mutations in the gene encoding the microtubule motor KIF5A result in skipping of exon 27 (KIF5A^ΔExon27) and the encoding of a protein with a novel 39 amino acid residue C-terminal sequence. Here, we report that expression of ALS-linked mutant KIF5A results in dysregulated motor activity, cellular mislocalization, altered axonal transport, and decreased neuronal survival. Single-molecule analysis revealed that the altered C terminus of mutant KIF5A results in a constitutively active state. Furthermore, mutant KIF5A possesses altered protein and RNA interactions and its expression results in altered gene expression/splicing. Taken together, our data support the hypothesis that causative ALS mutations result in a toxic gain of function in the intracellular motor KIF5A that disrupts intracellular trafficking and neuronal homeostasis.

了解疾病突变的致病机制对于推进治疗至关重要。编码微管运动 KIF5A 的基因中与 ALS 相关的突变导致外显子 27 (KIF5A ^ΔExon27 ) 的跳跃，并编码具有新的 39 个氨基酸残基 C 端序列的蛋白质。在此，我们报告 ALS 相关突变体 KIF5A 的表达会导致运动活动失调、细胞错误定位、轴突运输改变和神经元存活率降低。单分子分析表明，突变体 KIF5A 的 C 末端发生改变，导致组成型活性状态。此外，突变体 KIF5A 具有改变的蛋白质和 RNA 相互作用，其表达导致基因表达/剪接改变。综上所述，我们的数据支持这样的假设：致病性 ALS 突变会导致细胞内运动 KIF5A 功能毒性增强，从而破坏细胞内运输和神经元稳态。