Rapid assessment of human amylin aggregation and its inhibition by copper(II) ions by laser ablation electrospray ionization mass spectrometry with ion mobility separation

Journal Article · Wed Sep 09 00:00:00 EDT 2015 · Analytical Chemistry

DOI:https://doi.org/10.1021/acs.analchem.5b02217· OSTI ID:1344899

Li, Hang ^[1]; Ha, Emmeline ^[1]; Donaldson, Robert P. ^[1]; Jeremic, Aleksandar M. ^[1]; Vertes, Akos ^[1]

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1. The George Washington Univ., Washington, DC (United States)

Native electrospray ionization (ESI) mass spectrometry (MS) is often used to monitor noncovalent complex formation between peptides and ligands. The relatively low throughput of this technique, however, is not compatible with extensive screening. Laser ablation electrospray ionization (LAESI) MS combined with ion mobility separation (IMS) can analyze complex formation and provide conformation information within a matter of seconds. Islet amyloid polypeptide (IAPP) or amylin, a 37-amino acid residue peptide, is produced in pancreatic beta-cells through proteolytic cleavage of its prohormone. Both amylin and its precursor can aggregate and produce toxic oligomers and fibrils leading to cell death in the pancreas that can eventually contribute to the development of type 2 diabetes mellitus. The inhibitory effect of the copper(II) ion on amylin aggregation has been recently discovered, but details of the interaction remain unknown. Finding other more physiologically tolerated approaches requires large scale screening of potential inhibitors. In this paper, we demonstrate that LAESI-IMS-MS can reveal the binding stoichiometry, copper oxidation state, and the dissociation constant of human amylin–copper(II) complex. The conformations of hIAPP in the presence of copper(II) ions were also analyzed by IMS, and preferential association between the β-hairpin amylin monomer and the metal ion was found. The copper(II) ion exhibited strong association with the —HSSNN– residues of the amylin. In the absence of copper(II), amylin dimers were detected with collision cross sections consistent with monomers of β-hairpin conformation. When copper(II) was present in the solution, no dimers were detected. Thus, the copper(II) ions disrupt the association pathway to the formation of β-sheet rich amylin fibrils. Using LAESI-IMS-MS for the assessment of amylin–copper(II) interactions demonstrates the utility of this technique for the high-throughput screening of potential inhibitors of amylin oligomerization and fibril formation. Finally and more generally, this rapid technique opens the door for high-throughput screening of potential inhibitors of amyloid protein aggregation.

• Research Organization: George Washington Univ., Washington, DC (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES); National Institutes of Health (NIH)
• Grant/Contract Number: FG02-01ER15129; DK091845
• OSTI ID: 1344899
• Journal Information: Analytical Chemistry, Vol. 87, Issue 19; ISSN 0003-2700
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY