Investigating Natural Product Glycosides as Allosteric Modulators of P2X Purinergic Receptors

Allum, Elizabeth (2023) Investigating Natural Product Glycosides as Allosteric Modulators of P2X Purinergic Receptors. Doctoral thesis, University of East Anglia.

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Natural products have been used traditionally for thousands of years to treat a wide variety of ailments. The active compounds in Panax ginseng, the ginsenosides, have been shown to have numerous beneficial effects in conditions such as cancer and inflammation. Ginsenoside CK, a metabolite of the ginsenosides, has been shown to potentiate responses by the P2X7 and P2X4 purinergic ion channels. P2X ion channels are widespread throughout the body, although their potential as a novel drug target is only beginning to be explored.

Screening novel compounds at ion channels can be a time-consuming affair – to overcome this, a high-throughput screening assay was used to assess activity of natural product glycosides at multiple P2X receptors. Using this assay, activity of ginsenosides was confirmed at P2X1, P2X2, and P2X3 in addition to P2X4 and P2X7. The ginsenosides were found to potentiate responses to ATP at all P2X receptors tested, although to varying degrees, suggesting the potential for development of specific modulators for each receptor.

Next, the proposed binding pocket for the ginsenosides was explored in the P2X2 and P2X4 receptors and the degree of conservation between receptor subtypes considered. Whilst some residues, namely D318 (hP2X7 numbering) were conserved, multiple differences in proposed interactions with ginsenoside CK were uncovered. Residues around this region of the central vestibule were found to be key in determining receptor sensitivity to ATP, with mutations of residues D318 and L320 leading to enhanced sensitivity to ATP.

One particular residue, F322 in hP2X7, was found to have a key role in sensitivity of the receptor to ATP and modulation of dye uptake responses by ginsenosides. Potentiation by ginsenoside CK was retained in ion-based assays but reduced in dye uptake assays, highlighting the importance of using multiple assays to confirm findings.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Pharmacy
Depositing User: Chris White
Date Deposited: 12 Dec 2023 11:23
Last Modified: 12 Dec 2023 11:23

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