Ultrastructural studies of human patient brains with prion disease have revealed the accumulation
of misfolded PrP within dystrophic neurites inside endolysosomes. Other complex structures co-
exist within these dystrophies and are now considered common features of prion pathologies,
including autophagic vacuole-like membrane-bound organelles, lysosomal electron-dense
bodies, and enlarged endolysosomes. The mechanisms leading to the formation of these
structures remain unknown. Our studies have identified an endolysosomal pathway in mammalian
neurons that we call axonal rapid endosomal sorting and transport-dependent aggregation
(ARESTA), that drives the formation of neurotoxic axonal aggregates of a misfolded mutant prion
protein (PrP) inside endo-membrane structures that we call “endoggresomes”. The long-term goal
of this proposal is to characterize the endocytic pathways that play a role in the pathophysiology
of prion diseases, Alzheimer’s disease, and of Alzheimer’s disease related dementias, that will
provide actionable targets for their pharmacological treatment. The objectives of this proposal are
(i) to determine the generality of the ARESTA pathway in formation of endoggresomes in axons
of neurons expressing various familial PrP mutations, and to characterize the molecular and
ultrastructural architecture of neurotoxic endoggresomes; (ii) to determine the mechanisms of
mutant PrP endoggresome-mediated axonal impairments; and (iii) to determine how the
endolysosomal ARESTA pathway modulates the formation of axonal mutant PrP aggregates in
vivo. The central hypotheses are (i) ARESTA drives the formation of endoggresomes in various
familial prion diseases by interactions with co-factors within endocytic routes; (ii) mutant PrP
endoggresome-induced pathologies act as axonotoxicity hubs that inhibit neuronal function by
impairing local axonal cytoskeletal-organelle interactions, and (iii) endolysosomal pathways
modulate the formation and pathology of mutant PrP aggregates in vivo. The proposed research
is innovative because it provides a conceptual framework for developing models that include novel
endolysosomal pathway-mediated mechanisms to explain how intra-axonal aggregates form and
impair neuronal function in the prionopathies. The proposed research is significant because it
identifies the endocytic pathway and specifically ARESTA and endoggresomes, as anti-
aggregation targets for therapies to inhibit aggregate formation and reverse related pathologies.
As amyloid-b peptides, tau, and most proteins that misfold in neurodegeneration transit within
endocytic routes at some point in their processing routes, our findings are expected to be relevant
to Alzheimer’s disease and Alzheimer’s disease related dementias.