Potentiometric and spectroscopic studies on the copper(II) complexes of rat amylin fragments. The anchoring ability of specific non-coordinating side chains

Thermodynamic surprises of Cu(II)-amylin analogue complexes in membrane mimicking solutions

Membrane environment often has an important effect on the structure, and therefore also on the coordination mode of biologically relevant metal ions. This is also true in the case of Cu(II) coordination to amylin analogues—rat amylin, amylin_1–19, pramlintide and Ac-pramlintide, which offer N-terminal amine groups and/or histidine imidazoles as copper(II) anchoring sites. Complex stabilities are comparable, with the exception of the very stable Cu(II)–amylin_1–19, which proves that the presence of the amylin C-terminus lowers its affinity for copper(II); although not directly involved, its appropriate arrangement sterically prevents early metal binding. Most interestingly, in membrane-mimicking solution, the Cu(II) affinities of amylin analogues are lower than the ones in water, probably due to the crowding effect of the membrane solution and the fact that amide coordination occurs at higher pH, which happens most likely because the α-helical structure, imposed by the membrane-mimicking solvent, prevents the amides from binding at lower pH, requiring a local unwinding of the α-helix.

Neuroprotective Effects of the Amylin Analog, Pramlintide, on Alzheimer's Disease Are Associated with Oxidative Stress Regulation Mechanisms

Administration of the recombinant analog of the pancreatic amyloid amylin, Pramlintide, has shown therapeutic benefits in aging and Alzheimer's disease (AD) models, both on cognition and amyloid-β (Aβ) pathology. However, the neuroprotective mechanisms underlying the benefits of Pramlintide remain unclear. Given the early and critical role of oxidative stress in AD pathogenesis and the known reactive oxygen species (ROS) modulating function of amyloids, we sought to determine whether Pramlintide's neuroprotective effects involve regulation of oxidative stress mechanisms. To address this, we treated APP/PS1 transgenic mice with Pramlintide for 3 months, starting at 5.5 months prior to widespread AD pathology onset, and measured cognition (Morris Water Maze), AD pathology, and oxidative stress-related markers and enzymes in vivo. In vitro, we determined the ability of Pramlintide to modulate H2O2-induced oxidative stress levels. Our data show that Pramlintide improved cognitive function, altered amyloid-processing enzymes, reduced plaque burden in the hippocampus, and regulated endogenous antioxidant enzymes (MnSOD and GPx1) and the stress marker HO-1 in a location specific manner. In vitro, Pramlintide treatment in neuronal models reduced H2O2-induced endogenous ROS production and lipid peroxidation in a dose-dependent manner. Together, these results indicate that Pramlintide's benefits on cognitive function and pathology may involve antioxidant-like properties of this compound.

Metal binding selectivity of an N-terminally free multihistidine peptide HAVAHHH-NH2

For NH₂-HAVAHHH-NH₂ peptide the coordination to internal histidines is preferred for copper(ii), while it is the opposite for nickel(ii).

Complex formation of nickel(ii) and zinc(ii) ions with peptide fragments of rat amylin

For nickel(ii)-SSNX-NH₂ an equilibrium between the common (NH₂,3N⁻(peptide)) and (NH₂,2N⁻(peptide),N⁻(asparagine)) coordination modes was observed in a basic solution resulting in an increased stability of the complexes.

Coordination of Zn2+ and Cu2+ to the membrane disrupting fragment of amylin

Amylin, a small peptide co-secreted from pancreatic β-cells together with insulin, is one of the hallmarks of type II diabetes.