Conformational Characterization of Native and L17A/F19A-Substituted Dutch-Type β-Amyloid Peptides.

Kai-Cyuan He,Hsien-Bin Huang,Chung-Ying Tzeng,Shi-Jie Huang,Shing-Jong Huang,Chu-Ting Liang,Ta-Hsien Lin,Chi-Fon Chang,Yi-Ru Chen

doi:10.3390/ijms21072571

Abstract

Some mutations which occur in the α/β-discordant region (resides 15 to 23) of β-amyloid peptide (Aβ) lead to familial Alzheimer’s disease (FAD). In vitro studies have shown that these genetic mutations could accelerate Aβ aggregation. We recently showed that mutations in this region could alter the structural propensity, resulting in a different aggregative propensity of Aβ. Whether these genetic mutations display similar effects remains largely unknown. Here, we characterized the structural propensity and aggregation kinetics of Dutch-type Aβ40 (Aβ40(E22Q)) and its L17A/F19A-substituted mutant (Aβ40(L17A/F19A/E22Q)) using circular dichroism spectroscopy, nuclear magnetic spectroscopy, and thioflavin T fluorescence assay. In comparison with wild-type Aβ40, we found that Dutch-type mutation, unlike Artic-type mutation (E22G), does not reduce the α-helical propensity of the α/β-discordant region in sodium dodecyl sulfate micellar solution. Moreover, we found that Aβ40(L17A/F19A/E22Q) displays a higher α-helical propensity of the α/β-discordant region and a slower aggregation rate than Aβ40(E22Q), suggesting that the inhibition of aggregation might be via increasing the α-helical propensity of the α/β-discordant region, similar to that observed in wild-type and Artic-type Aβ40. Taken together, Dutch-type and Artic-type mutations adopt different mechanisms to promote Aβ aggregation, however, the L17A/F19A mutation could increase the α-helical propensities of both Dutch-type and Artic-type Aβ40 and inhibit their aggregation.

Highlights

On the basis of the amyloid cascade hypothesis [1,2], aggregation of β-amyloid peptide (Aβ) is a crucial factor for the neuronal damage that leads to Alzheimer’s disease (AD)
We characterized the effects of E22Q and L17A/F19A mutations on the structural propensities of wild-type Aβ40 and Aβ40(E22Q), respectively, by circular dichroism (CD) and Nuclear Magnetic Resonance (NMR) spectroscopy
We found that the E22Q mutation has no significant effect on the structural propensity of wild-type Aβ40, indicating that it does not promote aggregation by altering the α-helical propensity of the α/β-discordant region

Summary

Introduction

On the basis of the amyloid cascade hypothesis [1,2], aggregation of β-amyloid peptide (Aβ) is a crucial factor for the neuronal damage that leads to Alzheimer’s disease (AD). The clinical hallmarks of AD are neurofibrillary tangles and senile plaques within AD patients’ brains. The major components of these two hallmarks are tau protein and Aβ, respectively. It has been reported that increased Aβ production resulting from mutations in the processing enzymes of βAPP (such as β- and γ-secretase) [3] or βAPP mutations close to the cutting site of the processing enzymes [4,5] would cause family Alzheimer’s disease (FAD). Point mutations within the Aβ region of βAPP have been shown to cause family Alzheimer’s disease (FAD), such as mutations occurring at A21 [6], E22 [7,8], and D23 [9,10] of Aβ. Several studies have shown that E22G (Arctic-type mutation), E22Q (Dutch-type mutation), and D23N (Iowa-type mutation) mutations would alter the aggregation behavior [11] and structure property [12,13,14,15,16,17] of Aβ

Methods

Results

Conclusion