HSPA8 orchestrates SNARE complex assembly to drive extracellular vesicle-mediated spread of p-tau217 in Alzheimer's disease.

BACKGROUND: Dysregulation of multivesicular bodies (MVBs) in Alzheimer's disease (AD) contributes to aberrant tau secretion via extracellular vesicles (EVs). This may potentially explain our previous paradoxical observation of elevated free-form p-tau217 alongside reduced p-tau217+ EVs in plasma. This study aimed to investigate the mechanisms underlying the reduction of p-tau217+ EVs to uncover AD therapeutic targets. METHODS: By integrating hippocampal spatial transcriptomics of human brain with EV proteomics of cerebrospinal fluid, we identified key regulators of p-tau217+ EV release. Subsequently, we investigated the mechanisms underlying the synthesis and secretion of p-tau217+ EVs. The regulatory roles of these candidate proteins were systematically evaluated through shRNA knockdown and interference with a synthetic peptide in both Aβ42-treated cells and AD model mice. RESULTS: Heat shock protein family A member 8 (HSPA8) was identified as a crucial regulator of EV biogenesis and release, mediating the Aβ-SNAP29 interaction to disrupt SNARE complex assembly and impair p-tau217+ EV secretion. In AD models, HSPA8 inhibition with shRNA rescued p-tau217+ EVs and improved cognitive function. Additionally, blocking the Aβ-SNAP29 interaction with a selective peptide inhibitor for HSPA8 reversed the decline in p-tau217+ EV and cognitive deficits. CONCLUSIONS: These findings reveal a role of HSPA8 in regulating the MVB-mediated EV release and tau propagation, and highlight HSPA8 as a promising therapeutic target for modifying AD progression.