# A 16-amino acid peptide delays the progression of motor neuron degeneration and pathogenic symptoms in ALS models

## TL;DR

A 16-amino acid peptide delays motor neuron degeneration and improves symptoms in models of amyotrophic lateral sclerosis (ALS).

## Contribution

The discovery of two 16-amino acid peptides that mimic the neuroprotective effects of full-length Pgk1 in ALS models.

## Key findings

- FD-1 and FD-2 peptides reduce p-Cofilin and promote neurite outgrowth in ALS-like NSC34 cells.
- FD peptides rescue axonal growth and motor function in zebrafish and improve survival in ALS mice.
- FD peptides delay neuromuscular junction denervation and preserve motor neuron cell bodies in ALS models.

## Abstract

Amyotrophic lateral sclerosis (ALS) is a progressive motor neurons (MNs) degenerative disease. Despite advancements in understanding ALS pathogenesis, drug development lags far behind. The reduced secretion of phosphoglycerate kinase 1 (Pgk1) by NogoA-overexpressing muscle cells inhibits neurite outgrowth of MNs (NOMNs). However, administration of extracellular Pgk1 (ePgk1) reduces phospho-Cofilin (p-Cofilin), a growth cone collapse marker, and mitigates MN degeneration. This improves NOMNs in NSC34 neural cells and locomotion in SOD1-G93A ALS-mice by suppressing the p-P38-T180/p-MK2-T334/p-Limk1-S323/p-Cofilin-S3 signaling pathway. Here, we identified two Pgk1-based 16-amino acid (aa) short peptides, FD-1 and FD-2, with neuroprotective effects equivalent to those of full-length ePgk1. Administration of FD-1 or FD-2 (FD-1/-2) reduced p-Cofilin and promoted NOMNs in NSC34 ​cells cultured in conditioned medium obtained from NogoA-overexpressing muscle cells. Furthermore, we found that exogenous addition of FD-1/-2 to the culture medium attenuated the accumulation of phospho-Tau-S396 and the cytoplasmic mislocalization of transactive response DNA binding protein of 43 ​kDa (TDP-43) in oxidative-stressed ALS-like SOD1-G93A NSC34 ​cells. In FD-1/-2-injected zebrafish embryos, we observed increased caudal primary MNs branching. In C9orf72-knockdown and hTDP-43-G348C mRNA overexpressing zebrafish embryos injected with FD-1/-2, axonal growth and motor function were rescued. Moreover, intravenous injection of FD-1/-2 in SOD1-G93A ALS-mice delayed denervation of neuromuscular junction, preserved cell bodies of MNs in the ventral horn of spinal cord, increased grip strength, improved locomotion and prolonged survival. Therefore, both 16-aa short FD peptides are functionally equivalent to full-length 417-aa ePgk1 and thus promising therapeutic short peptides for the treatment of ALS.