Both beta sheet breaker and alpha helix forming pentapeptide inhibits protein fibrillation: Implication for the treatment of amyloid disorders

Abstract

For the first time, the effect of two novel designed pentapeptides on amyloid growth of human insulin using combined biophysical, microscopic, cell viability and computational approaches. Collective experimental data from ThT, ANS, and TEM demonstrate that in spite of having contrasting features, both peptides can effectively inhibit amyloid formation by prolonging lag phase, slowing down aggregation rate, and reducing final fibril formation (up to 84.26% and 85.24% by P1 and P7 respectively). Although pure amyloid caused profound cellular toxicity in SH-SY5Y neuronal cells, amyloid formed in the presence of peptides showed much reduced cellular toxicity. Such an inhibitory effect can be attributed to interference with the structural transition of insulin toward β-sheet structure by peptides. Furthermore, molecular dynamic simulations confirm that peptide preferentially binds to nearby region which is more prone to form aggregates that consequently disrupts self-assembly into amyloid fibrils (P1 and P7 possess inhibition constant value of 0.000183 and 0.000216 nm, respectively), supporting our experimental observations. This study underscores the information about the sequence based inhibition mechanism of peptides that might dictate their inhibition or modulation capacity, which might be helpful in designing anti-amyloid therapeutics.