Protein misfolding results in a plethora of known diseases
such
as Alzheimer’s disease, Parkinson’s disease, Huntington’s
disease, transthyretin-related amyloidosis, type 2 diabetes, Lewy
body dementia, and spongiform encephalopathy. To provide a diverse
portfolio of therapeutic small molecules with the ability to reduce
protein misfolding, we evaluated a set of 13 compounds: 4-(benzo[d]thiazol-2-yl)aniline (BTA) and its derivatives containing
urea (1), thiourea (2), sulfonamide (3), triazole (4), and triazine (5) linker. In addition, we explored small modifications on a very
potent antioligomer 5-nitro-1,2-benzothiazol-3-amine (5-NBA) (compounds6–13). This study aims to define the activity of BTA
and its derivatives on a variety of prone-to-aggregate proteins such
as transthyretin (TTR81–127, TTR101–125), α-synuclein (α-syn), and tau isoform 2N4R (tau 2N4R)
through various biophysical methods. Thioflavin T (ThT) fluorescence
assay was used to monitor fibril formation of the previously mentioned
proteins after treatment with BTA and its derivatives. Antifibrillary
activity was confirmed using transmission electron microscopy (TEM).
Photoreactive cross-linking assay (PICUP) was utilized to detect antioligomer
activity and lead to the identification of 5-NBA (at low micromolar
concentration) and compound13(at high concentration)
as the most promising in reducing oligomerization. 5-NBA and not BTA
inhibited the inclusion formation based on the cell-based assay using
M17D neuroblastoma cells that express inclusion-prone αS-3K::YFP.
5-NBA abrogated the fibril, oligomer, and inclusion formation in a
dose-dependent manner. 5-NBA derivatives could be the key to mitigate
protein aggregation. In the future, the results made from this study
will provide an initial platform to generate more potent inhibitors
of α-syn and tau 2N4R oligomer and fibril formation.