Cell-Penetrating Chaperone Peptide Prevents Protein Aggregation and Protects against Cell Apoptosis

Many of the newly discovered therapeutic peptides and molecules are limited by their inability to cross the cell membrane. In the present study, a cell-penetrating peptide (CPP), VPTLK, derived from Ku70 protein, is employed to facilitate the entry of a minichaperone across the cell membrane. Previous studies suggest that the minichaperone peptide representing the chaperone site in alpha A-crystallin, which can inhibit protein aggregation associated with prote opathies, has therapeutic potential. A synthetic minichaperone is prepared by fusing the VPTLK sequence to N-terminus of minichaperone (FVIFLDVKHF-SPEDLTVKGRD) to get VPTLKFVIFLDVKHFSPEDLTVKGRD peptide, which is called CPPGRD. The amino acids, glycine-arginine-aspartic acid (GRD), are added to increase the solubility of the peptide. The chaperone-like function of CPPGRD is measured using unfolding conditions for alcohol dehydrogenase and alpha-lactalbumin. The antiapoptotic action of the peptide chaperone is evaluated using H2O2-induced Cos-7 and ARPE-19 cell apoptosis assays. The results show that the CPPGRD has both chaperone function and antiapoptotic activity. Additionally, the CPPGRD is found to prevent beta-amyloid fibril formation and suppress beta-amyloid toxicity. The present study demonstrates that the CPPGRD protects unfolding proteins from aggregation and prevents cellular apoptosis. Therefore, the CPPGRD is a minichaperone with potential to become a therapeutic agent for protein aggregation diseases.