Huntington disease (HD) is a progressive neurodegenerative disease caused by an expanded CAG repeat in the HTT (huntingtin) gene, leading to the accumulation of mutant HTT (mHTT). IL17A (interleukin 17A), a proinflammatory cytokine primarily secreted by Th17 and γδ T cells, has been implicated in immune-mediated neurodegeneration. However, the role of IL17A in the pathogenesis of HD remains poorly understood. Here, we identify IL17A as a critical pathogenic factor in HD that promotes neuroinflammation, mHTT aggregation, and autophagy-lysosomal dysfunction. IL17A disrupts autophagic flux by downregulating CTSB and CTSD, inducing SQSTM1/p62 and MAP1LC3B-II/LC3-II accumulation, and impairing lysosomal reformation. Mechanistically, IL17A suppresses lysosomal biogenesis by inhibiting the nuclear translocation of TFE3. This regulation occurs via a novel GSK3B/GSK-3β-TFE3 signaling pathway. Therapeutic neutralization of IL17A with a monoclonal antibody (IL17A mAb) ameliorates disease phenotypes in R6/2 HD mice, improving motor performance, extending survival, and reducing gliosis. IL17A mAb also attenuates mHTT aggregation and enhances neuroprotective signaling, as evidenced by increased expression of DLG4/PSD-95, phosphorylated CREB1, and BDNF. Moreover, IL17A mAb restores autophagy-lysosomal function by facilitating the clearance of protein aggregates and upregulating lysosomal enzymes and biogenesis markers, including CTSB, CTSD, PIP5K1A, and LAMP2. These findings establish IL17A as a key modulator of HD pathophysiology and highlight IL17A inhibition as a promising therapeutic strategy for targeting autophagy-lysosomal dysfunction in HD.
