PIKfyve activity is required for lysosomal trafficking of tau aggregates and tau seeding

Alberto Carpinteiro Soares,Andreia Ferreira,Jonas Mariën,Charlotte Delay,Edward Lee,John Q Trojanowski,Dieder Moechars,Wim Annaert,Louis De Muynck

doi:10.1016/j.jbc.2021.100636

Abstract

Tauopathies, such as Alzheimer's disease (AD), are neurodegenerative disorders characterized by the deposition of hyperphosphorylated tau aggregates. Proteopathic tau seeds spread through the brain in a temporospatial pattern, indicative of transsynaptic propagation. It is hypothesized that reducing the uptake of tau seeds and subsequent induction of tau aggregation could be a potential approach for abrogating disease progression in AD. Here, we studied to what extent different endosomal routes play a role in the neuronal uptake of preformed tau seeds. Using pharmacological and genetic tools, we identified dynamin-1, actin, and Rac1 as key players. Furthermore, inhibition of PIKfyve, a protein downstream of Rac1, reduced both the trafficking of tau seeds into lysosomes and the induction of tau aggregation. Our work shows that tau aggregates are internalized by a specific endocytic mechanism and that their fate once internalized can be pharmacologically modulated to reduce tau seeding in neurons.

Highlights

Tauopathies, such as Alzheimer’s disease (AD), are neurodegenerative disorders characterized by the deposition of hyperphosphorylated tau aggregates
To study the molecular mechanisms governing the internalization of tau aggregates, we developed an imaging assay that uses K18 preformed fibril (PFF) labeled with either a pH-sensitive dye— pHrodo, for live-cell imaging – or a pH-insensitive dye—Alexa Fluor 488 (AF488), for immunocytochemistry
Tau pathology spreading over synaptically connected areas of the brain is a common feature in tauopathies [56]

Summary

Introduction

Tauopathies, such as Alzheimer’s disease (AD), are neurodegenerative disorders characterized by the deposition of hyperphosphorylated tau aggregates. Our work shows that tau aggregates are internalized by a specific endocytic mechanism and that their fate once internalized can be pharmacologically modulated to reduce tau seeding in neurons. Endosomal trafficking and sorting attract increasing attention in the AD field, with growing evidence showing that disruption in these mechanisms have an important impact in the development of AD pathology [22, 23]. This is underscored by genome-wide association studies and exome sequencing that identified risk genes involved in endocytic transport regulation, including BIN1, PICALM, CD2AP, and SORLA1 [24, 25]. In this work we have used fluorophore labeled preformed fibrils (PFFs) of recombinant truncated tau (K18P301L) to study in detail the molecular mechanisms that are responsible for the internalization of seeds in mouse primary hippocampal neurons and how modulating these pathways could interfere with

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