Involvement of P2X4 and P2Y12 receptors in ATP-induced microglial chemotaxis

We previously reported that extracellular ATP induces membrane ruffling and chemotaxis of microglia and suggested that their induction is mediated by the Gi/o‐protein coupled P2Y12 receptor (P2Y12R). Here we report discovering that the P2X4 receptor (P2X4R) is also involved in ATP‐induced microglial...

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Bibliographic Details
Published in:Glia 2007-04, Vol.55 (6), p.604-616
Main Authors: Ohsawa, Keiko, Irino, Yasuhiro, Nakamura, Yasuko, Akazawa, Chihiro, Inoue, Kazuhide, Kohsaka, Shinichi
Format: Article
Language:English
Subjects:
Adenosine Triphosphate - metabolism
Adenosine Triphosphate - pharmacology
Animals
Animals, Newborn
ATP
Cells, Cultured
chemotaxis
Chemotaxis - drug effects
Chemotaxis - physiology
Down-Regulation - physiology
Enzyme Inhibitors - pharmacology
Lentivirus
Membrane Proteins - agonists
Membrane Proteins - antagonists & inhibitors
Membrane Proteins - metabolism
microglia
Microglia - drug effects
Microglia - metabolism
Oncogene Protein v-akt - drug effects
Oncogene Protein v-akt - metabolism
P2X4
P2Y12
Phosphatidylinositol 3-Kinases - antagonists & inhibitors
Phosphatidylinositol 3-Kinases - metabolism
Phosphorylation - drug effects
Purinergic P2 Receptor Agonists
Purinergic P2 Receptor Antagonists
Rats
Rats, Wistar
Receptors, Purinergic P2 - metabolism
Receptors, Purinergic P2X4
Receptors, Purinergic P2Y12
RNA Interference - physiology
Signal Transduction - drug effects
Signal Transduction - physiology
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Summary:We previously reported that extracellular ATP induces membrane ruffling and chemotaxis of microglia and suggested that their induction is mediated by the Gi/o‐protein coupled P2Y12 receptor (P2Y12R). Here we report discovering that the P2X4 receptor (P2X4R) is also involved in ATP‐induced microglial chemotaxis. To understand the intracellular signaling pathway downstream of P2Y12R that underlies microglial chemotaxis, we examined the effect of two phosphatidylinositol 3′‐kinase (PI3K) inhibitors, wortmannin, and LY294002, on chemotaxis in a Dunn chemotaxis chamber. The PI3K inhibitors significantly suppressed chemotaxis without affecting ATP‐induced membrane ruffling. ATP stimulation increased Akt phosphorylation in the microglia, and the increase was reduced by the PI3K inhibitors and a P2Y12R antagonist. These results indicate that P2Y12R‐mediated activation of the PI3K pathway is required for microglial chemotaxis in response to ATP. We also found that the Akt phosphorylation was reduced when extracellular calcium was chelated, suggesting that ionotropic P2X receptors are involved in microglial chemotaxis by affecting the PI3K pathway. We therefore tested the effect of various P2X4R antagonists on the chemotaxis, and the results showed that pharmacological blockade of P2X4R significantly inhibited it. Knockdown of the P2X4 receptor in microglia by RNA interference through the lentivirus vector system also suppressed the microglial chemotaxis. These results indicate that P2X4R as well as P2Y12R is involved in ATP‐induced microglial chemotaxis. © 2007 Wiley‐Liss, Inc.
ISSN:0894-1491
1098-1136
DOI:10.1002/glia.20489