Detection of Amyloid β Oligomers with RNA Aptamers in App^{NL-G-F/NL-G-F} Mice: A Model of Arctic Alzheimer’s Disease

Abstract

RNA aptamers have garnered attention for diagnostic applications due to their ability to recognize diverse targets. Oligomers of 42-mer amyloid β-protein (Aβ42), whose accumulation is relevant to the pathology of Alzheimer’s disease (AD), are among the most difficult molecules for aptamer recognition because they are prone to aggregate in heterogeneous forms. In addition to designing haptens for in vitro selection of aptamers, the difficulties involved in determining their effect on Aβ42 oligomerization impede aptamer research. We previously developed three RNA aptamers (E22P-AbD4, -AbD31, and -AbD43) with high affinity for protofibrils (PFs) derived from a toxic Aβ42 dimer. Notably, these aptamers recognized diffuse staining, which likely originated from PFs or higher-order oligomers with curvilinear structures in a knock-in App NL-G-F/NL-G-F mouse, carrying the Arctic mutation that preferentially induced the formation of PFs, in addition to a PS2Tg2576 mouse. To determine which oligomeric sizes were mainly altered by the aptamer, ion mobility–mass spectrometry (IM–MS) was carried out. One aptamer, E22P-AbD43, formed adducts with the Aβ42 monomer and dimer, leading to suppression of further oligomerization. These findings support the utility of these aptamers as diagnostics for AD.

Aptamers targeting amyloidogenic proteins and their emerging role in neurodegenerative diseases

“…Several software tools have been developed to address this challenge, such as QGRS (Quadruplex forming G-Rich Sequences) Mapper ( 133 ), GRSdb ( 134 ), and QuadBase2 ( 135 ), which are specific to prediction of G-quadruplexes in RNA and DNA sequences. For example, the formation of G-quadruplex in an RNA aptamer against Aβ42 protofibrils predicted by QGRS Mapper was validated by detection of a negative peak at ∼240 nm and a positive peak at ∼265 nm in the CD spectrum ( 136 ), and by observation of a 1650 cm −1 absorbance peak in the Attenuated Total Reflection-FTIR spectrum ( 137 ), both of which are unique to guanine carbonyl groups in a G-quadruplex ( 58 , 59 ). Similarly, a DNA aptamer (T-SO508) against αSyn oligomers was predicted to contain a G-quadruplex by QGRS Mapper, and the prediction was confirmed by CD spectroscopy ( 81 ).…”

“…The first example of a successful generation of aptamers against Aβ oligomers we are aware of is by Murakami et al. , who developed RNA aptamers termed E22P-AbD4, -AbD31, and -AbD43 against Aβ42 protofibrils ( 58 , 59 ). To select the aptamers, a dimer of E22P-Aβ42 was used in which the monomers were tethered covalently by a bivalent amino acid linker in place of Val40, within the C-terminal hydrophobic region of Aβ42 ( Fig.…”

“…The aptamer also inhibited dose-dependently the neurotoxicity of both the E22P-Aβ42 dimer and Aβ42 in the neuroblastoma cell line SH-SY5Y cells. Computational and two-dimensional structure analysis of E22P-AbD43 suggested that preferential binding of the aptamer to Aβ42 protofibrils compared with fibrils might be related to formation of a G-quadruplex structure, implying the presence of a common structure in protofibrils made of either the synthetic dimer or native Aβ42 protofibrils ( 59 ).…”

A Multi-Chamber Paper-Based Platform for the Detection of Amyloid β Oligomers 42 via Copper-Enhanced Gold Immunoblotting

“…Although the structural difference between Aβ40 and Aβ42 is only two amino acid residues, Aβ42 exhibits a higher neurotoxicity than Aβ40 [8,9]. Aβ42 oligomers (AβO42) play a critical role in neuronal death and cognitive dysfunction, which inhibits neuronal viability more than 10-fold compared to fibrils and more than 40-fold compared to peptide, with induced inhibition significant at 10 nM [10][11][12][13]. Hence, due to the significant inhibitory effect of low concentrations of AβO42, the early detection Biomolecules 2021, 11, 948 2 of 9 of AβO42 is essential for the development of a highly sensitive biosensor, contributing to the efficient intervention of AD.…”

Bioinspired Synthesis of ZnO@polydopamine/Au for Label-Free Photoelectrochemical Immunoassay of Amyloid-β Protein

“…( Nakamura, Kaneko et al, 2018 ; Laís Canniatti, Isabella et al, 2019 ) In blood, the physiological concentrations of Aβ is several picograms per milliliter. To date, a great deal of sensing techniques has been performed to detect Aβ protein, including ELISA( Linan, Son et al, 2016 ), ion mobility-mass spectrometry (IM-MS)( Obata, Murakami et al, 2020 ), colorimetric biosensor( Xi, Shuangling et al, 2021 ), electrochemical( Carneiro, Loureiro et al, 2017 ), fluorescence( Lee, Park et al, 2019 ; Wang, Du et al, 2020 ; Wen-Kai, Liu et al, 2021 ), surface-enhanced Raman spectroscopy( Yang, Hwang et al, 2019 ), and photoelectrochemical (PEC) immunosensors( Wang, Fan et al, 2018 ). Among them, the PEC biosensor is an innovative and attractive analytical technique for quantitative study in the biological analysis due to its intrinsic merits such as label-free, high signal-to-noise ratio, rapid response, and is more readily miniaturized.…”