Tau assemblies enter the cytosol in a cholesterol sensitive process essential to seeded aggregation

Abstract

Accumulating evidence supports a prion-like mechanism in the spread of assembled tau in neurodegenerative diseases. Prion-like spread is proposed to require the transit of tau assemblies to the interior of neurons in order to seed aggregation of native, cytosolic tau. This process is poorly understood and remains largely hypothetical. Here, we develop sensitive techniques to quantify the cytosolic entry of tau in real-time. We find that tau does not promote its own entry but, rather, is wholly dependent on cellular machinery. We find that entry to the widely used reporter cell line HEK293 requires clathrin whereas entry to neurons does not. Cholesterol depletion or knockdown of cholesterol transport protein Niemann-Pick type C1 in neurons renders cells highly vulnerable to cytosolic entry and seeded aggregation. Our findings establish entry as the rate-limiting step in seeded aggregation and demonstrate that dysregulated cholesterol, a feature of several neurodegenerative diseases, potentiates tau aggregation. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=170 SRC="FIGDIR/small/449238v3_ufig1.gif" ALT="Figure 1"> View larger version (23K): org.highwire.dtl.DTLVardef@1849023org.highwire.dtl.DTLVardef@13129eorg.highwire.dtl.DTLVardef@2b4736org.highwire.dtl.DTLVardef@15038ac_HPS_FORMAT_FIGEXP M_FIG Graphical Abstract C_FIG