Convergent TBK1 loss of function drives gasdermin E dependent pyroptosis and motor neuron degeneration across ALS genotypes

Abstract

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive loss of upper and lower motor neurons, yet it is unknown whether diverse genetic risks converge on a shared pathogenic pathway. Here we identify a common mechanism linking TBK1 insufficiency to inflammatory cell death across distinct ALS genotypes. Whole-exome sequencing of 8 familial ALS patients revealed that 3 of them carried pathogenic variants, namely TBK1 (R573H), TDP-43 (G298V)/GARS (I44M)/SETX (L1304W), or SOD1 (G94R)/SQSTM1 (G262R). Motor neurons differentiated from patient iPSCs, despite their different mutations, consistently exhibited axonal and neurite shortening, reduced TBK1 activity, increased phosphorylated TDP-43 with cytoplasmic aggregation, and co-assembly of caspase-8/7 with the pyroptosis executor gasdermin E (GSDME). Neuroinflammatory stimulation further enhanced caspase-8/7 and GSDME cleavage, increased RIPK1 phosphorylation and suppressed TBK1 activation in patient-derived motor neurons, whereas TBK1 knockdown in SH-SY5Y cells recapitulated these phenotypes. Furthermore, a generated humanized TBK1 R573H knock-in mouse developed progressive motor deficits accompanied by spinal motor-neuron loss, neuroinflammation, and TDP-43 pathology. In these mice, LPS challenge produced increased cleavage of GSDME and caspase-7, along with a marked upregulation of p-TDP-43 expression in vulnerable neurons. Together, these data identify TBK1 loss of function as an upstream driver of a caspase-8/7-GSDME pyroptotic program in motor neurons and provide a mechanistic bridge between neuroinflammation, TDP-43 proteinopathy, and neurodegeneration. Targeting the TBK1-caspase-GSDME axis may offer a tractable strategy for disease modification in ALS.