A peptide rich in glycine-serine-alanine repeats ameliorates Alzheimer-type neurodegeneration

Repeated amino acid sequences in proteins are widely found, and the glycine-serine-alanine repeat is an element with a general propensity to form β-sheet aggregates as found in key pathological factors, in several neurodegenerative diseases. Such properties of this repeat may guide development of disease-modifying therapies for neurodegenerative disease. However, details of its role and underlying mechanism(s) remain largely unknown.

Actions of specific glycine-serine-alanine repeat peptides (SNPs), especially SNP-9, on Alzheimer's disease (AD)-like abnormalities were evaluated in transgenic mice and Caenorhabditis elegans, and in rat and cell models. Entry of SNPs into the brain, SNP activity in neuronal cells and peptide entry into cells were analysed in vivo and in vitro. Cell-free systems and the yeast two-hybrid system were also used to explore possible targets of SNP-9, and interactions of potential targets with SNP-9 were confirmed in cell-based systems.

We first identified SNP-9 as a potent neuroprotective peptide with the activity to decrease oligomeric amyloid β (Aβ) via co-assembling with the toxic Aβ oligomer to form hetero-oligomers. Also, calcyclin-binding protein was found to act as a SNP-9-binding protein, by screening of a human brain cDNA library. Such binding showed that SNP-9 could regulate the abnormal hyperphosphorylation of tau via calcyclin-binding protein.

Our study provides a foundation for development of SNPs, especially SNP-9, as potential therapeutic interventions for AD. We propose SNP-9 as a potential therapeutic agent for the treatment of AD.