Binding of mycotoxins to proteins involved in neuronal plasticity: a combined in silico/wet investigation

Abstract

We have applied a combined computational procedure based on inverse and direct docking in order to identify putative protein targets of a panel of mycotoxins and xenobiotic compounds that can contaminate food and that are known to have several detrimental effects on human health. This procedure allowed us to identify a panel of human proteins as possible targets for aflatoxins, gliotoxin, ochratoxin A and deoxynivalenol. Steady-state fluorescence and microscale thermophoresis experiments allowed us to confirm the binding of some of these mycotoxins to acetylcholinesterase and X-linked neuroligin 4, two proteins involved in synapse activity and, particularly for the second protein, neuronal plasticity and development. Considering the possible involvement of X-linked neuroligin 4 in the etiopathogenesis of autism spectrum syndrome, this finding opens up a new avenue to explore the hypothetical role of these xenobiotic compounds in the onset of this pathology.

Figure 1

Results of blind docking between some mycotoxins and selected targets. (A) Aflatoxin M1 and tankyrase; (B) glutamate carboxypeptidase 2 and protonated ochratoxin; (C) aflatoxin B1 and AChE; (D) aflatoxin B2 and NLGN4X. The “canonical” binding site of the proteins is represented in spacefill mode, whereas the ligand is shown in stick mode. The picture has been created by Discovery Studio.

Figure 2

Results of focused docking for AChE and NLGN4X. (A) Aflatoxin B1 and AChE; (B) aflatoxin B2 and NLGN4X. The representation is as in Fig. 1.

Figure 3

Fluorescence emission spectra of NLGN4X – aflatoxin B2 (A), NLGN4X – deoxynivalenol (B), NLGN4X – gliotoxin (C). The interaction of the mycotoxins with NLGN4X was registered by Trp fluorescence emission variation. All measurements were performed in PBS buffer pH 7.4 at 25 °C.

Figure 4

Interaction of NLGN4X with the selected ligand Aflatoxin B2 (A), deoxynivalenol (B) and gliotoxin (C). The curve shows the best theoretical fit to the analysed experimental data, R² = 0.98.

Figure 5

Interaction of the aflatoxin B1 with AChE measured by Trp fluorescence emission variation. The measurements was performed in PBS buffer pH 7.4 at 37 °C.

Figure 6

MST assay of NLGN4X with Gliotoxin (A), Aflatoxin B2 (B) and Aflatoxin B1 (C). All measurements were performed in PBS buffer pH 7.4 at 25 °C.

Figure 7

MST assay of AChE with Aflatoxin B1. The measurements were performed in Hepes buffer pH 8 at 25 °C.