ProNGF elicits retrograde axonal degeneration of basal forebrain neurons via p75NTR and induction of APP

Basal forebrain cholinergic neurons (BFCNs) extend long projections to multiple targets in the brain to regulate cognitive functions, and are compromised in numerous neurodegenerative disorders. Our previous study showed that injury to the target region of these neurons affects their viability in vivo. Moderate cortical injury in mice promoted a significant increase in proneurotrophins in the injured cortex, leading to the retrograde loss of BFCNs ipsilateral to the injury via the p75 neurotrophin receptor (p75NTR). We determined that stimulation of BFCN axon terminals with proNGF elicited retrograde degeneration of the axons leading to cell death of these neurons in vitro. Our current study investigates mechanisms of axonal p75NTR signaling, and shows that retrograde transport and local axonal protein synthesis are necessary for proNGF induced retrograde degeneration initiated at the axon terminal. Analysis of the nascent axonal proteome revealed numerous newly synthesized proteins after stimulation of axon terminals with proNGF. Pathway analysis showed that amyloid precursor protein (APP) was a key upstream regulator. Our results show a functional role for APP in promoting proNGF induced BFCN axonal degeneration and cell death.