Figure 1.

Cell-to-Sources of extracellular tau and -cell spreading. The established view has long considered the presence of tau in the brain parenchyma or in the CSF as a consequence of tau protein being released after cell lysis. However, extracellular tau appears to result from a physiological process independent of cell death, as tau being can be released from cell lines and neurons via multiple pathways, either in naked form or vesicle-associated. In addition, tau misfolding in diseased brain leads to abnormal conformations of tau that can be taken up by surrounding neurons. Thus, pathological progression could involve transmission of tau protein through a prion-like mechanism resulting in neurodegeneration in susceptible brain regions.