Key aromatic/hydrophobic amino acids controlling a cross-amyloid peptide interaction versus amyloid self-assembly

Abstract

The interaction of the intrinsically disordered polypeptide islet amyloid polypeptide (IAPP), which is associated with type 2 diabetes (T2D), with the Alzheimer's disease amyloid-β (Aβ) peptide modulates their self-assembly into amyloid fibrils and may link the pathogeneses of these two cell-degenerative diseases. However, the molecular determinants of this interaction remain elusive. Using a systematic alanine scan approach, fluorescence spectroscopy, and other biophysical methods, including heterocomplex pulldown assays, far-UV CD spectroscopy, the thioflavin T binding assay, transmission EM, and molecular dynamics simulations, here we identified single aromatic/hydrophobic residues within the amyloid core IAPP region as hot spots or key residues of its cross-interaction with Aβ40(42) peptide. Importantly, we also find that none of these residues in isolation plays a key role in IAPP self-assembly, whereas simultaneous substitution of four aromatic/hydrophobic residues with Ala dramatically impairs both IAPP self-assembly and hetero-assembly with Aβ40(42). Furthermore, our experiments yielded several novel IAPP analogs, whose sequences are highly similar to that of IAPP but have distinct amyloid self- or cross-interaction potentials. The identified similarities and major differences controlling IAPP cross-peptide interaction with Aβ40(42) its amyloid self-assembly offer a molecular basis for understanding the underlying mechanisms. We propose that these insights will aid in designing intervention strategies and novel IAPP analogs for the management of type 2 diabetes, Alzheimer's disease, or other diseases related to IAPP dysfunction or cross-amyloid interactions.

Peptid‐basierte molekulare Strategien zum Einsatz bei Proteinfehlfaltung, Proteinaggregation und Zelldegeneration

“…[41] Diese so genannten "Macrocyclic Inhibitory Peptides" (MCIPs) ahmen funktionelle (inhibitorische) IAPP-Interaktionsflächen nach, während sie zugleich minimale IAPP-basierte Erkennungselemente beibehalten (Abbildung 7 c). [41,47] [6,49] Auf der Suche nach Strategien zur Reduktion der nicht-nativen Aggregation von Insulin, die zu Komplikationen bei seiner biomedizinischen Anwendbarkeit führt, identifizierten wir IAPP-GI als einen nanomolaren Inhibitor. [11d] Erwartungsgemäß interferiert die IAPP-GI-Insulin-Wechselwirkung nicht mit der Insulinfunktion, da IAPP-GI ein Analog des nativ vorkommenden Insulin-Interaktionspartners IAPP ist.…”

Membranotropic peptides mediating viral entry

“…Among these, gH625, represents a key achievement in grasping the role of hydrophobic viral peptides . The peptide contains residues critical for interaction such as aromatic residues (tryptophan and tyrosines) which are known for their preferred location at the membrane interface and for their ability to facilitate oligomerization together with numerous hydrophobic residues (glycines, leucines, alanines) which are critical for membrane insertion; at the C‐terminus there is an arginine residue which is key for establishing peptide–lipid interactions. gH625 penetrates into membranes from its N‐terminal side, and assumes an amphipathic helical conformation .…”

Designed Macrocyclic Peptides as Nanomolar Amyloid Inhibitors Based on Minimal Recognition Elements

“…[7a, 8] In fact, the formation of high-affinity nonfibrillar IAPP-Ab40(42) heteroassemblies has been shown to suppress Ab40(42) amyloid self-assembly. [4,9] Accordingly,w eh ave recently designed linear peptides mimicking putative IAPP self-/cross-interaction surfaces (called "interaction surface mimics" (ISMs)) by linking IAPP (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) with double Nmethylated IAPP(22-28) using different tripeptide units. [4,9] Accordingly,w eh ave recently designed linear peptides mimicking putative IAPP self-/cross-interaction surfaces (called "interaction surface mimics" (ISMs)) by linking IAPP (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) with double Nmethylated IAPP(22-28) using different tripeptide units.…”

“…To reduce the size of 1,w es ynthesized its analogue 2 lacking the region IAPP (8)(9)(10)(11)(12)(13). N-terminal truncation was based on the suggestion that IAPP(14-18) and IAPP(22-28) mediate key interactions for both IAPP self-and heteroassembly.…”

“…Interestingly,t he far-UV CD spectra of both cyclic and linear peptides had similar shapes and were indicative of random-coil and b-sheet/b-turn content in an approximately 1:1ratio (Figure 1f). [5,9] Aiming to minimize IAPP-derived elements,w enexta sked if these four residues and the RRR linker would be sufficient for amyloid inhibitory function and synthesized analogue 2b with 7o ut of the 11 non-Gly residues of 2a replaced with Gly (except for Cys); only the side chains of the above four residues were maintained (Scheme 1). [5] Indeed, fluorescence spectroscopic titrations revealed midnanomolar apparent K d values for interactions of cyclic inhibitors 1a and 2a with N-terminally fluorescently labeled Ab40 or IAPP as previously found for 1,w hereas much weaker binding was found for the non-inhibitor 2 (see the Supporting Information, Figures S2 and S3, and Table S2).…”