Innate immune crosstalk in ALS/FTD pathogenesis

Marked by protein aggregation, impaired proteostasis, organelle stress, and chronic neuroinflammation, amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) form a clinically, genetically, and pathologically overlapping disease spectrum. Increasing evidence indicates that innate immune activation is not merely a secondary response to neuronal injury, but an active driver of disease progression. In this review, we elaborate on how ALS/FTD-associated genetic lesions and pathogenic protein aggregates, including TDP-43, SOD1, FUS, and C9orf72-derived dipeptide repeat proteins, engage three interconnected innate immune pathways: cGAS-STING, NLRP3 inflammasomes, and TREM2-DAP12 signaling. We further highlight emerging crosstalk among these pathways, in which cGAS-STING and NLRP3 reinforce inflammatory signaling, while NLRP3-driven TREM2 shedding may impair microglial clearance and perpetuate proteostatic failure. Understanding this immune network may help define disease subtypes, identify biomarkers, and guide combinatorial therapeutic strategies that suppress harmful inflammation while preserving protective microglial functions.