Negative regulation of TREM2-mediated C9orf72 poly-GA clearance by the NLRP3 inflammasome

Expansion of the hexanucleotide repeat GGGGCC in the C9orf72 gene is the most common genetic factor in amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Poly-Gly-Ala (poly-GA), one form of dipeptide repeat proteins (DPRs) produced from GGGGCC repeats, tends to form neurotoxic protein aggre-gates. The C9orf72 GGGGCC repeats and microglial receptor TREM2 are both associated with risk for ALS/ FTD. The role and regulation of TREM2 in C9orf72-ALS/FTD remain unclear. Here, we found that poly-GA pro-teins activate the microglial NLRP3 inflammasome to produce interleukin-1b (IL-1b), which promotes ADAM10-mediated TREM2 cleavage and inhibits phagocytosis of poly-GA. The inhibitor of the NLRP3 inflam-masome, MCC950, reduces the TREM2 cleavage and poly-GA aggregates, resulting in the alleviation of motor deficits in poly-GA mice. Our study identifies a crosstalk between NLRP3 and TREM2 signaling, suggesting that targeting the NLRP3 inflammasome to sustain TREM2 is an approach to treat C9orf72- ALS/FTD.

Automated summary

Expansion of the GGGGCC repeat in the C9orf72 gene is the most common genetic factor in ALS and FTD. The produced poly-GA proteins tend to form neurotoxic aggregates. The relationship between C9orf72 and TREM2 in ALS/FTD is still unclear.