The design of inhibitors of protein-protein interactions mediating amyloid self-assembly is a major challenge mainly due to the dynamic nature of the involved structures and interfaces. Interactions of amyloidogenic polypeptides with other proteins are important modulators of self-assembly. Here we present a hot-segment-linking approach to design a series of mimics of the IAPP cross-amyloid interaction surface with Aβ (ISMs) as nanomolar inhibitors of amyloidogenesis and cytotoxicity of Aβ, IAPP, or both polypeptides. The nature of the linker determines ISM structure and inhibitory function including both potency and target selectivity. Importantly, ISMs effectively suppress both self- and cross-seeded IAPP self-assembly. Our results provide a novel class of highly potent peptide leads for targeting protein aggregation in Alzheimer's disease, type 2 diabetes, or both diseases and a chemical approach to inhibit amyloid self-assembly and pathogenic interactions of other proteins as well.

The selective incorporation of N‐methyl groups in the highly amyloidogenic and cytotoxic sequence of the type 2 diabetes islet amyloid polypeptide (IAPP) generates a unique class of soluble and nontoxic IAPP mimics. These polypeptides combine potent IAPP receptor agonism with nanomolar‐affinity inhibitory potential on the amyloid formation and cell‐damaging effects of both IAPP and the Alzheimer's β‐amyloid peptide (Aβ40).

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.

Wir danken A. Kazantzis für seine Beiträge zur Peptidsynthese, A. Kastenmüller und S. Weinkauf für Hilfe bei der TEM und J. Bernhagen für hilfreiche Diskussionen. Diese Arbeit wurde gefçrdert durch die Deutsche Forschungsgemeinschaft (DFG). IAPP = Insel-Amyloid-Polypeptid. Hintergrundinformationen zu diesem Beitrag sind im WWW unter http://dx.doi.org/10.1002/ange.201302840 zu finden.

Der Entwurf von Inhibitoren von Protein-Protein-Wechselwirkungen, die die amyloidogene Selbstassemblierung herbeiführen, ist ein sehr anspruchsvolles Vorhaben. Dies liegt an der dynamischen Natur der beteiligten Strukturen und Proteinflächen. Die Wechselwirkungen von amyloidogenen Polypeptiden mit anderen Proteinen sind wichtige Modulatoren ihrer Selbstassoziation. Hier stellen wir eine Hot-Spot-Segmentverknüpfungsstrategie zum Entwurf einer Serie von Mimetika der IAPP-Kreuzinteraktionsfläche mit Ab (ISMs) als nanomolare Inhibitoren der Amyloidogenese und Zelltoxizität von Ab,I APP oder beiden Polypeptiden vor.D abei bestimmt die Natur des Verknüpfungselements die Struktur der ISMs und ihre inhibitorische Funktion, im Bezug auf sowohl Inhibitorpotenz als auchZ ielmolekül-Selektivität. Die ISMs sind außerdem in der Lage,z usätzlichz ur Selbst-auchd ie kreuznukleierte IAPP-Selbstassoziation effektiv zu unterdrücken. Unsere Ergebnisse bieten eine neuartige Klasse von hochpotenten Peptidleitstrukturen, die auf die Hemmung der Proteinaggregation in der Alzheimer-Krankheit, dem Typ-2-Diabetes oder beiden Krankheiten abzielt, sowie eine chemische Strategie zur Inhibition der amyloiden Selbstassoziation und der pathogenenen Wechselwirkungen aucha nderer Proteine.