Helical sulfonyl-γ-AApeptides modulating Aβ oligomerization and cytotoxicity by recognizing Aβ helix.

In contrast to prevalent strategies which make use of β-sheet mimetics to block Aβ fibrillar growth, in this study, we designed a series of sulfonyl-γ-AApeptide helices that targeted the crucial α-helix domain of Aβ13-26 and stabilized Aβ conformation to avoid forming the neurotoxic Aβ oligomeric β-sheets. Biophysical assays such as amyloid kinetics and TEM demonstrated that the Aβ oligomerization and fibrillation could be greatly prevented and even reversed in the presence of sulfonyl-γ-AApeptides in a sequence-specific and dose-dependent manner. The studies based on circular dichroism, Two-dimensional nuclear magnetic resonance spectroscopy (2D-NMR) spectra unambiguously suggested that the sulfonyl-γ-AApeptide Ab-6 could bind to the central region of Aβ 42 and induce α-helix conformation in Aβ. Additionally, Electrospray ionisation-ion mobility spectrometry-mass spectrometry (ESI-IMS-MS) was employed to rule out a colloidal mechanism of inhibitor and clearly supported the capability of Ab-6 for inhibiting the formation of Aβ aggregated forms. Furthermore, Ab-6 could rescue neuroblastoma cells by eradicating Aβ-mediated cytotoxicity even in the presence of pre-formed Aβ aggregates. The confocal microscopy demonstrated that Ab-6 could still specifically bind Aβ 42 and colocalize into mitochondria in the cellular environment, suggesting the rescue of cell viability might be due to the protection of mitochondrial function otherwise impaired by Aβ 42 aggregation. Taken together, our studies indicated that sulfonyl-γ-AApeptides as helical peptidomimetics could direct Aβ into the off-pathway helical secondary structure, thereby preventing the formation of Aβ oligomerization, fibrillation and rescuing Aβ induced cell cytotoxicity.