Molecular Tweezers Inhibit Islet Amyloid Polypeptide Assembly and Toxicity by a New Mechanism

Abstract

In type-2 diabetes (T2D), islet amyloid polypeptide (IAPP) self-associates into toxic assemblies causing islet β-cell death. Therefore, preventing IAPP toxicity is a promising therapeutic strategy for T2D. The molecular tweezer CLR01 is a supramolecular tool for selective complexation of K residues in (poly)peptides. Surprisingly, it inhibits IAPP aggregation at substoichiometric concentrations even though IAPP has only one K residue at position 1, whereas efficient inhibition of IAPP toxicity requires excess CLR01. The basis for this peculiar behavior is not clear. Here, a combination of biochemical, biophysical, spectroscopic, and computational methods reveals a detailed mechanistic picture of the unique dual inhibition mechanism for CLR01. At low concentrations, CLR01 binds to K1, presumably nucleating nonamyloidogenic, yet toxic, structures, whereas excess CLR01 binds also to R11, leading to nontoxic structures. Encouragingly, the CLR01 concentrations needed for inhibition of IAPP toxicity are safe in vivo, supporting its development toward diseasemodifying therapy for T2D.

Molecular tweezers for lysine and arginine – powerful inhibitors of pathologic protein aggregation

“…Islet amyloid polypeptide (IAPP) is a 37-residue polypeptide hormone constituting the major component of the pancreatic islet amyloid associated with type-2 diabetes (T2D). 41 The results of the fluorimetric titration experiments of the tweezers 1c–f (each substituted with two ionic groups) and the monophosphate tweezers 1h–n with these peptides are listed in Table 1 and 2.…”

Structural, morphological, and functional diversity of amyloid oligomers

“…Partially disordered Ab oligomers formed in the presence of polyphenols were non-toxic [31,136,137], whereas more structured Ab oligomers were toxic. Lysine-binding small molecules ('molecular tweezers') were shown to promote formation of non-toxic oligomers from a variety of amyloidogenic proteins and peptides [138][139][140][141][142] by modulating the oligomer structure. In case of Ab, they have been shown to compact the structures of dimers and tetramers and prevented formation of more toxic higher-order oligomers [143].…”

The Lys-Specific Molecular Tweezer, CLR01, Modulates Aggregation of the Mutant p53 DNA Binding Domain and Inhibits Its Toxicity

“…Of the amyloidogenic proteins for which CLR01's inhibitory activity was studied previously (14,27,36,37), Aβ40, Aβ42, tau, α-synuclein and islet amyloid polypeptide are intrinsically disordered, insulin, β 2 -microglobulin, and TTR are natively structured, and calcitonin is a relatively short peptide that is partially 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 relative to the structured proteins, as would be expected for a partially structured peptide (14).…”