Journal of Biological Chemistry
Volume 284, Issue 38, 18 September 2009, Pages 25813-25822
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Membrane Transport, Structure, Function, and Biogenesis
A Functional P2X7 Splice Variant with an Alternative Transmembrane Domain 1 Escapes Gene Inactivation in P2X7 Knock-out Mice*

https://doi.org/10.1074/jbc.M109.033134Get rights and content
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The ATP-activated P2X7 receptor channel is involved in immune function and inflammatory pain and represents an important drug target. Here we describe a new P2X7 splice variant (P2X7(k)), containing an alternative intracellular N terminus and first transmembrane domain encoded by a novel exon 1 in the rodent P2rx7 gene. Whole cell patch clamp recordings of the rat isoform expressed in HEK293 cells revealed an 8-fold higher sensitivity to the agonist Bz-ATP and much slower deactivation kinetics when compared with the P2X7(a) receptor. Permeability measurements in Xenopus oocytes show a high permeability for N-methyl-d-glucamine immediately upon activation, suggesting that the P2X7(k) channel is constitutively dilated upon opening. The rates of agonist-induced dye uptake and membrane blebbing in HEK cells were also increased. PCR analyses and biochemical analysis by SDS-PAGE and BN-PAGE indicate that the P2X7(k) variant escapes gene deletion in one of the available P2X7−/− mice strains and is strongly expressed in the spleen. Taken together, we describe a novel P2X7 isoform with distinct functional properties that contributes to the diversity of P2X7 receptor signaling. Its presence in one of the P2X7−/− strains has important implications for our understanding of the role of this receptor in health and disease.

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The nucleotide sequence(s) reported in this paper has been submitted to the Gen-BankTM/EBI Data Bank with accession number(s) FJ436444 and FJ436445.

*

This work was supported by the Deutsche Forschungsgemeinschaft (Grants NI 592/4 and NI 592/5 to A. N.), the German Israeli Foundation (to F. S.), the Interreg IV (AdMiN) (to D. C. G.), and the Biotechnology and Biological Sciences and Research Council (Grant BB/F001320/1to R. M.-L.).

The on-line version of this article (available at http://www.jbc.org) contains supplemental movies 1–10.

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Present address: University of Washington, School of Medicine, Dept. of Biological Structure, Seattle, WA 98195.