Comparative studies on peptides representing the so-called tachykinin-like region of the Alzheimer Aβ peptide [Aβ(25-35)]

In an attempt to answer the question of whether or not the so-called tachykinin-like region of the Alzheimer β-amyloid protein [Aβ(25-35)] can act as a tachykinin, the sequences Aβ(25-35), Aβ(25-35)amide and their norleucine-35 and phenylalanine-31 analogues were synthesized. These peptides were examined with ligand binding studies, electron microscopy, CD and NMR. In all cases some differences were found between the Aβ(25-35) analogue and the corresponding Phe³¹ peptide. In addition, in ligand displacement studies on tachykinin NK1 receptors, only the Phe³¹ analogue showed activity comparable to that of genuine tachykinins. We conclude that peptides based on Aβ(25-35) but with a Phe residue at position 31 do display properties typical of a tachykinin, but that peptides with Ile at this position do not.