A Novel Pentapeptide Inhibitor Reduces Amyloid Deposit Formation by Direct Interaction with hIAPP.

Yue Shi,Wu Lv,Chengshuo Zhang,Jialin Zhang,Ao Jiao

doi:10.1155/2019/9062032

Abstract

Backgrounds The presence of amyloid deposits of human islet amyloid polypeptide (hIAPP) in islet β-cells has been associated with type 2 diabetes occurrence and islet graft failure. Self-assembly into oligomers and fibrils during the process of aggregation by hIAPP can lead to failure and depletion of β-cells. Studies have shown that some critical regions of hIAPP might contribute to the aggregation. Thus, many studies focused on finding the effective molecules, especially the short-peptide inhibitors, that bind to these regions and disrupt the aggregation of hIAPP. In the present study, a novel pentapeptide inhibitor Phe-Leu-Pro-Asn-Phe (FLPNF) was designed and its effectiveness on the inhibition of the formation of amyloid deposits was examined. Methods The binding mode between FLPNF and hIAPP was performed using molecular docking. The effectiveness of FLPNF on inhibiting hIAPP amyloid aggregation was tested by Thioflavin T (ThT) staining. Furthermore, negative stain electron microscopy was used to observe hIAPP fibrils. A biolayer interferometry analysis was used to identify the interaction between FLPNF and hIAPP. In addition, the cytotoxicity toward INS-1 cells was tested by a cell proliferation assay. Results FLPNF was predicted to have a compact conformation to bind at the site of hIAPP. FLPNF strongly inhibited the amyloid aggregation of hIAPP at a 10 : 1 molar ratio in vitro. Coincubation of FLPNF with hIAPP decreased the amount of hIAPP fibrils. Furthermore, a direct interaction between FLPNF and hIAPP was confirmed. FLPNF could also decrease the cytotoxic effect of hIAPP. Conclusions The novel pentapeptide inhibitor FLPNF was constructed and inhibited the aggregation through direct binding to hIAPP. It is considered a suitable inhibitor for hIAPP amyloid deposit formation.

Highlights

Human islet amyloid polypeptide, known as amylin, is a kind of hormone secreted by β-cells consisting of 37 amino acid residues [1, 2]
Two hydrogen bond interactions were observed between the residues Asn-4 and Phe-5 of FLPNF and the residues Asn-31 and Arg-11 of Human islet amyloid polypeptide (hIAPP), respectively, which were the main interaction between them (Figure 1(b))
Discussion hIAPP is the major component of amyloid deposition in the islets of type 2 diabetes [15] and contributes to the islet transplant failure in type 1 diabetes [13, 16]

Summary

Introduction

Human islet amyloid polypeptide (hIAPP), known as amylin, is a kind of hormone secreted by β-cells consisting of 37 amino acid residues [1, 2]. Since hIAPP self-assembles to form amyloid deposits containing parallel β-sheet structure [17], it has been found that some amyloidogenic regions of hIAPP promote the formation of β-sheet aggregations. Short peptides were designed based on specific amino acid sequences of the amyloid-beta peptide (Aβ) in Alzheimer’s disease. These could inhibit the β-sheet aggregations of Aβ and were named as beta-sheet breaker peptides [23, 24]. A pentapeptide inhibitor Phe-Leu-ProAsn-Phe (FLPNF) that contains only five amino acids has been designed It was designed based on 11-15 residues (RLANF) of hIAPP, because it was included in the critical amyloidogenic region 8-20 and has one aromatic amino acid phenylalanine (F). The morphological changes of hIAPP deposits were observed by transmission electron microscopy (TEM)

Materials and Methods

Results

Discussion