A Function for EHD Family Proteins in Unidirectional Retrograde Dendritic Transport of BACE1 and Alzheimer's Disease Ab Production

Abnormal accumulation of beta-secretase (BACE1) in dystrophic neurites and presynaptic beta-amyloid (A beta) production contribute to Alzheimer's disease pathogenesis. Little, however, is known about BACE1 sorting and dynamic transport in neurons. We investigated BACE1 trafficking in hippocampal neurons using live-cell imaging and selective labeling. We report that transport vesicles containing internalized BACE1 in dendrites undergo exclusive retrograde transport toward the soma, whereas they undergo bidirectional transport in axons. Unidirectional dendritic transport requires Eps15-homology-domain containing (EHD) 1 and 3 protein function. Furthermore, loss of EHD function compromises dynamic axonal transport and overall BACE1 levels in axons. EHD1/3 colocalize with BACE1 and APP beta-C-terminal fragments in hippocampal mossy fiber terminals, and their depletion in neurons significantly attenuates A beta levels. These results demonstrate unidirectional endocytic transport of a dendritic cargo and reveal a role for EHD proteins in neuronal BACE1 transcytosis and A beta production, processes that are highly relevant for Alzheimer's disease.