Repair of amyloid-β-induced plasma membrane damage via coordinated P21-activated kinase activation and Rab3a-directed vesicle fusion.

The interaction of amyloid-β (Aβ) peptides with the plasma membrane (PM) is a potential trigger that initiates the formation of higher-order aggregates, membrane alterations/damage, and progressive neurotoxicity in Alzheimer's disease (AD). Recent studies showed neurons initiate PM repair upon damage induced by Aβ aggregates, and dysfunctional repair mechanisms contribute to neurodegeneration. This study uncovers a previously unrecognized molecular coupling between Rab3a-mediated exocytosis and pPAK1-driven endocytosis as a pivotal mechanism of PM repair in neuronal cells and primary neurons exposed to aggregation-prone oligomers of Aβ (oAβ). Unlike earlier reports that broadly associated PM damage and repair with Aβ aggregates, we specifically demonstrate that toxic oAβ1-42, but not oAβ1-40, provokes a highly efficient Rab3a-dependent exocytic repair response, tightly synchronized with pPAK1-mediated endocytosis. Using TIRF microscopy, we dissected the kinetics of vesicle fusion at nanometer-scale resolution and revealed that repair is initiated within minutes of oAβ1-42 exposure, with Rab3a activity dominating the critical first hour of response. Perturbation of this system-via IPA-3-mediated PAK1 inhibition or shRNA knockdown of Rab3a-abolished repair efficiency, establishing a direct causal link between these pathways. Furthermore, the long-term accumulation of oAβ in lysosomes was found to disrupt Rab3a recycling, implicating lipid-microdomain dynamics in the progressive failure of repair machinery in AD model, underscoring their physiological relevance. This study uniquely defines the synchronized action of exocytosis-endocytosis in PM repair via pPAK and Rab3a coordinated machinery as a critical neuronal survival strategy and highlights its specific failure as a mechanistic contributor to AD pathogenesis.