Localization of the noncovalent binding site between amyloid-β-peptide and oleuropein using electrospray ionization FT-ICR mass spectrometry

Abstract

Abnormal accumulation and aggregation of amyloid-␤-peptide (A␤) eventually lead to the formation and cerebral deposition of amyloid plaques, the major pathological hallmark in Alzheimer's disease (AD). Oleuropein (OE), an Olea europaea L. derived polyphenol, exhibits a broad range of pharmacological properties, such as antioxidant, anti-inflammatory, and antiatherogenic, which could serve as combative mechanisms against several reported pathways involved in the pathophysiology of AD. The reported noncovalent interaction between A␤ and OE could imply a potential antiamyloidogenic role of the latter on the former via stabilization of its structure and prevention of the adaptation of a toxic ␤-sheet conformation. The established ␤-sheet conformation of the A␤ hydrophobic carboxy-terminal region and the dependence of its toxicity and aggregational propensity on its secondary structure make the determination of the binding site between A␤ and OE highly important for assessing the role of the interaction. In this study, two different proteolytic digestion protocols, in conjunction with high-sensitivity electrospray ionization mass spectrometric analysis of the resulting peptide fragments, were used to determine the noncovalent binding site of OE on A␤ and revealed the critical regions for the interaction. and its aggregational properties depend on both the peptide concentration and conformation, as well as on the solution conditions and pH [2,3]. It has been reported that reduction of the A␤ production, by controlling the cleavage of the larger transmembrane amyloid precursor protein (APP), or inhibition of its aggregation by using small molecules, which may interact noncovalently with A␤ and stabilize its structure, could serve as preventive or therapeutic approaches against AD [4]. In general, interruption of noncovalent interactions between protein and peptides, or even more between proteins/peptides and ligands can cause abnormalities, which often lead to diseases [5]. One interaction of this kind has been established between the Olea europaea derived bioactive compound, oleuropein (OE), and A␤ by means of electrospray ionization mass spectrometry (ESI-MS) [6]. This interaction could prove potent in inhibiting its aggregation.OE is a polyphenol extracted from the fruits and leaves of Olea europaea L. and possesses a wide range of pharmacological properties, such as antioxidant [7][8][9], anti-inflammatory [10, 11], antiatherogenic [12-14], antibacterial [15][16][17], and anticancer [18,19]. Moreover, OE and its metabolites have been shown to be potent against contemporary diseases, such as HIV [20,21] and osteoporosis [22,23]. Interestingly, in vitro [24] and epidemiological [25] studies demonstrated the positive impact of polyphenols on the onset of age-related disorders, such as dementia [26,27].It is regarded that the pathophysiology of AD is tangled and many theories have been proposed to illumine its mechanism. Free radical reactions and oxidative stress [28,29], as well as unregulated immune response [30,3...

Oleuropein aglycon prevents cytotoxic amyloid aggregation of human amylin☆

“…Recently, oleuropein has been shown to form a noncovalent complex with the Aβ peptide [19,20]. Here, we report on the oleuropein aglycon interference with hIAPP aggregation and on its protection against aggregate cytotoxicity using a RIN-5F rat insulinoma cell model.…”

Small Amphipathic Molecules Modulate Secondary Structure and Amyloid Fibril-forming Kinetics of Alzheimer Disease Peptide Aβ1–42

“…On the basis of previous work on various other small molecule modulators of A␤ aggregation, such as 8-hydroxyquinolines (42), oleuropein (43,44), ␣-helix stabilizers (45), various chaperones (46,47), anesthetics (48,49), and gangliosides (50), two potential binding sites can be suggested. From these previous studies it is clear that A␤ contains a small molecule binding site near residues 10 -20 and a second binding site in the C-terminal glycine zipper motif.…”

The use of mass spectrometry to study amyloid‐β peptides

“…Therefore, ESI/MS represents an optimal tool not only to study possible inhibitors of Ab aggregation but also to determine the stability of the Ab complexes. Moreover, the Ab:OE noncovalent complex was further studied to determine the noncovalent binding site of OE on Ab, by applying two different proteolytic digestion protocols, in conjunction with highsensitivity ESI/MS analysis of the resulting peptide fragments, and revealed the critical regions for such interaction (Bazoti et al, 2008). In the latter study, a home-built apparatus controlled the direct infusion of the samples, whereas one end of the capillary was coated by a conductive graphite/polymer layer of ''black dust'' that functioned as a sheathless electrospray needle so that no sheath flow or nebulizing gas was used.…”