Mechanism of Tau protein incorporation into exosomes via cooperative recognition of KFERQ-like motifs by LAMP2A and HSP70.

Aggregates of the tau protein is a well-known hallmark of Alzheimer's disease (AD) and other Tauopathies, such as Frontotemporal dementia (FTD). Tau can be propagated between nerve cells or brain areas, similar as 'seed'. As a member of small extracellular vesicles, exosomes may act as one of the most important 'seeding machines', disseminating toxic tau and phosphorylated tau proteins between cells and thereby amplifying their neurotoxic effects. Therefore, exploring the underlying mechanisms of Tau loading into exosomes is of great importance. In this study, human P301L tau transfections were established in SH-SY5Y cells (SY5Y-EGFP-TauP301L cells). The content of membrane protein LAMP2A and HSP70 proteins was significantly increased in the SY5Y-EGFP-Tau P301L cells compared to control group. Tau containing KFERQ-like motifs pentapeptide interact with LAMP2A and HSP70, forming a multi-protein complex, which can be loaded into a subpopulation of exosomes. Moreover, knockout of LAMP2A significantly reduced the content of Tau protein in exosomes obtained from SY5Y-EGFP-Tau P301L cells. Thus, exosome-mediated secretion of tau protein may depend on the formation of multi-protein (KFERQ-like motif pentapeptide in tau,LAMP2A and HSP70) complex. These findings revealed the presence of a novel mechanism by which release of tau through exosome secretion pathway and that LAMP2A may play an important role in the regulation of exosome-mediated secretion of tau, which may become a potential therapeutic target for AD or other Tauopathies.