Chlorpyrifos Oxon-Induced Isopeptide Bond Formation in Human Butyrylcholinesterase

Overview

Journal Molecules

Publisher MDPI

Specialty Biology

Date 2020 Jan 30

PMID 31991818

Citations 1

Authors

Kevser Biberoglu

Ozden Tacal

Lawrence M Schopfer

Oksana Lockridge

Affiliations

Soon will be listed here.

Abstract

A newly recognized action of organophosphates (OP) is the ability to crosslink proteins through an isopeptide bond. The first step in the mechanism is covalent addition of the OP to the side chain of lysine. This activates OP-lysine for reaction with a nearby glutamic or aspartic acid to make a gamma glutamyl epsilon lysine bond. Crosslinked proteins are high molecular weight aggregates. Our goal was to identify the residues in the human butyrylcholinesterase (HuBChE) tetramer that were crosslinked following treatment with 1.5 mM chlorpyrifos oxon. High molecular weight bands were visualized on an SDS gel. Proteins in the gel bands were digested with trypsin, separated by liquid chromatography and analyzed in an Orbitrap mass spectrometer. MSMS files were searched for crosslinked peptides using the Batch-Tag program in Protein Prospector. MSMS spectra were manually evaluated for the presence of ions that supported the crosslinks. The crosslink between Lys544 in VLEMTGNIDEAEWEWKAGFHR and Glu542 in VLEMTGNIDEAEWEWK satisfied our criteria including that of spatial proximity. Distances between Lys544 and Glu542 were 7.4 and 9.5 Å, calculated from the cryo-EM (electron microscopy) structure of the HuBChE tetramer. Paraoxon ethyl, diazoxon, and dichlorvos had less pronounced effects as visualized on SDS gels. Our proof-of-principle study provides evidence that OP have the ability to crosslink proteins. If OP-induced protein crosslinking occurs in the brain, OP exposure could be responsible for some cases of neurodegenerative disease.

Citing Articles

Dichlorvos-induced formation of isopeptide crosslinks between proteins in SH-SY5Y cells.

Schopfer L, Lockridge O Anal Biochem. 2022; 655:114844.

PMID: 35961399 PMC: 10368009. DOI: 10.1016/j.ab.2022.114844.

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