# Neurotrophic factor-α1/carboxypeptidase E regulates critical protein networks to rescue neurodegeneration, defective synaptogenesis and impaired autophagy in Alzheimer’s disease mice

## TL;DR

A gene therapy using NF-α1/CPE improves memory and reduces Alzheimer's disease pathology in mice by regulating key proteins involved in brain health.

## Contribution

This study reveals new proteins and pathways regulated by NF-α1/CPE gene therapy in Alzheimer's disease.

## Key findings

- NF-α1/CPE-E342Q gene therapy prevents memory loss and neurodegeneration in AD mice.
- Proteomic analysis identified over 2000 proteins affected, including those involved in synaptogenesis and autophagy.
- Two new proteins, Snx4 and Trim28, linked to Aβ and tau pathology, are down-regulated by NF-α1/CPE.

## Abstract

The global aging population is increasingly inflicted with Alzheimer’s disease (AD), but a cure is still unavailable. Neurotrophic factor-α1/carboxypeptidase E (NF-α1/CPE) gene therapy has been shown to prevent and reverse memory loss and pathology in AD mouse models. However, the mechanisms of action of NF-α1/CPE are not fully understood. We investigated if a non-enzymatic form of NF-α1/CPE-E342Q is efficient in reversing AD pathology and carried out a proteomic study to uncover the mechanisms of action of NF-α1/CPE in AD mice.

AAV-human NF-α1/CPE or a non-enzymatic form, NF-α1/CPE-E342Q, was delivered into the hippocampus of 3 × Tg-AD male mice. The effects on cognitive function, neurodegeneration, synaptogenesis and autophagy were investigated. A quantitative proteomic analysis of the hippocampus was carried out.

Hippocampal delivery of AAV-NF-α1/CPE-E342Q prevented memory loss, neurodegeneration and microglial activation in 3 × Tg-AD mice, indicating that the action is independent of its enzymatic activity. Quantitative proteomic analysis of the hippocampus of 3 × Tg-AD mice revealed differential expression of > 2000 proteins involving many metabolic pathways after NF-α1/CPE gene therapy. Of these, two new proteins, Snx4 and Trim28, which increase Aβ production and tau levels, respectively, were down-regulated by NF-α1/CPE. Western blot analysis verified their reduction in AAV-NF-α1/CPE-treated 3 × Tg-AD mice compared to untreated mice. Our proteomic analysis indicated synaptic organization as the top signaling pathway altered in response to CPE expression. Synaptic markers PSD95 and Synapsin1 were decreased in 3 × Tg-AD mice and were restored with AAV-NF-α1/CPE treatment. Proteomic analysis hypothesized involvement of autophagic signaling pathway. Indeed, multiple protein markers of autophagy were down-regulated in 3 × Tg-AD mice, accounting for impaired autophagy. NF-α1/CPE gene therapy upregulated the levels of these proteins in 3 × Tg-AD mice, thereby reversing autophagic impairment.

This study uncovered vast actions of NF-α1/CPE in restoring expression of networks of critical proteins including those necessary for maintaining neuronal survival, synaptogenesis and autophagy, while down-regulating many proteins that promote tau and Aβ accumulation to reverse memory loss and AD pathology in 3 × Tg-AD mice. AAV-NF-α1/CPE gene therapy uniquely targets many metabolic levels, offering a promising holistic approach for AD treatment (Graphical Abstract).

The online version contains supplementary material available at 10.1186/s40035-025-00520-6.