TDP-43 Secretion via Extracellular Vesicles Is Regulated by Macroautophagy

The pathological accumulation of the nuclear protein TDP-43 (TAR DNA-binding protein 43 kDa) in the cytoplasm is characteristic of amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD-TDP), and its spread through the brain and spinal cord is closely associated with the progression of these two diseases. However, the mechanisms through which the TDP-43 pathology propagates throughout the central nervous system remain unclear. We recently reported the role of (macro)autophagy in the secretion of TDP-43 via extracellular vesicles (EVs). We found that among the autophagy modulators, bafilomycin A1 (Baf) and GRN (granulin precursor) deficiency impair the formation of autolysosomes and promote the secretion of TDP-43 by EVs. TDP-43 loading on EVs involves autophagy-related proteins and the knockdown of TDP-43 augmented Baf-induced EV release. Thus, our results suggest that the loss-of-function of TDP-43 accelerates release of EVs possibly derived from autophagosomes, which may mediate cell-to-cell spread of the TDP-43 pathology.