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Title: Functional Characterization of Intracellular Dictyostelium discoideum P2X Receptors
Authors: Ennion, Steven J.
Ludlow, Melanie J.
Dural, Latha
First Published: Dec-2009
Publisher: American Society for Biochemistry and Molecular Biology
Citation: Journal of Biochemical Chemistry, 2009, 284, pp. 35227-35239.
Abstract: Indicative of cell surface P2X ion channel activation, extracellular ATP evokes a rapid and transient calcium influx in the model eukaryote Dictyostelium discoideum. Five P2X-like proteins (dP2XA–E) are present in this organism. However, their roles in purinergic signaling are unclear, because dP2XA proved to have an intracellular localization on the contractile vacuole where it is thought to be required for osmoregulation. To determine functional properties of the remaining four dP2X-like proteins and to assess their cellular roles, we recorded membrane currents from expressed cloned receptors and generated a quintuple knock-out Dictyostelium strain devoid of dP2X receptors. ATP evoked inward currents at dP2XB and dP2XE receptors but not at dP2XC or dP2XD. β,γ-Imido-ATP was more potent than ATP at dP2XB but a weak partial agonist at dP2XE. Currents in dP2XB and dP2XE were strongly inhibited by Na+ but insensitive to copper and the P2 receptor antagonists pyridoxal phosphate-6-azophenyl-2′,4′-disulfonic acid and suramin. Unusual for P2X channels, dP2XA and dP2XB were also Cl−-permeable. The extracellular purinergic response to ATP persisted in p2xA/B/C/D/E quintuple knock-out Dictyostelium demonstrating that dP2X channels are not responsible. dP2XB, -C, -D, and -E were found to be intracellularly localized to the contractile vacuole with the ligand binding domain facing the lumen. However, quintuple p2xA/B/C/D/E null cells were still capable of regulating cell volume in water demonstrating that, contrary to previous findings, dP2X receptors are not required for osmoregulation. Responses to the calmodulin antagonist calmidazolium, however, were reduced in p2xA/B/C/D/E null cells suggesting that dP2X receptors play a role in intracellular calcium signaling.
DOI Link: 10.1074/jbc.M109.045674
ISSN: 0021-9258
eISSN: 1083-351X
Type: Article
Rights: This research was originally published in Journal of Biochemical Chemistry. Ludlow,Melanie J.; Dural, Latha; Ennion, Steven J. Functional Characterization of Intracellular Dictyostelium discoideum P2X Receptors. Journal of Biochemical Chemistry. 2009; Vol:35227-35239. © the American Society for Biochemistry and Molecular Biology. This is the publisher-produced PDF as the authors published this paper under the "Author's Choice" option. The published article can be found at: , doi: 10.1074/jbc.M109.045674
Appears in Collections:Published Articles, Dept. of Cell Physiology and Pharmacology

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