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

Abstract

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. 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. 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. 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.