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Open Access Research

Gain and loss of function of P2X7 receptors: mechanisms, pharmacology and relevance to diabetic neuropathic pain

Daniel Ursu1, Philip Ebert2, Emily Langron1, Cara Ruble2, Leanne Munsie2, Wei Zou3, Bonnie Fijal2, Yue-Wei Qian2, Terry A McNearney2, Adrian Mogg1, Olivera Grubisha1, Kalpana Merchant2 and Emanuele Sher1*

Author Affiliations

1 Lilly Research Centre, Eli Lilly & Co. Ltd., Sunninghill Road, GU20 6PH Windlesham, Surrey, UK

2 Lilly Corporate Center, Eli Lilly and Company, 46285 Indianapolis, Indiana, USA

3 InVentiv Clinical Health, LLC, 504 Carnegie Center, 08540 Princeton, NJ, USA

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Molecular Pain 2014, 10:37  doi:10.1186/1744-8069-10-37

Published: 16 June 2014

Abstract

Background

Genetic causes of exaggerated or reduced pain sensitivity in humans are well known. Recently, single nucleotide polymorphisms (SNPs) in the gene P2RX7, coding for the ATP-gated ion channel P2X7, have been described that cause gain-of-function (GOF) and loss-of-function (LOF), respectively of this channel. Importantly, P2RX7 SNPs have been associated with more or less severe pain scores in patient suffering of post-mastectomy pain and osteoarthritis.

Results

The functional consequences of some P2RX7 SNPs (rs208294 (His155Tyr), rs1718119 (Ala348Thr) and rs3751143 (Glu496Ala)) were studied in recombinant cells in vitro. Our findings suggest a correlation between GOF and LOF of P2X7 and actual channel protein expression. Both channel and pore function for these mutant P2X7 receptors changed in parallel to protein levels. On the other hand, the mutant receptors did not differ in their sensitivity to known P2X7 agonists and antagonists. We further demonstrated that in patients with diabetic peripheral neuropathic pain (DPNP), the presence of the GOF SNPs rs208294 (His155Tyr) and rs1718119 (Ala348Thr) is associated, in females, with higher pain intensity scores.

Conclusions

Our present results confirm the physiological relevance of some of the SNPs in the P2RX7 gene and show that the presence of these genetic variants correlates with pain sensitivity also in a diabetic neuropathic pain patient population.

Keywords:
P2X receptors; Single nucleotide polymorphism; Gain-of-function; Pain