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P2X7/P2Z purinoreceptor-mediated activation of transcription factor NFAT in microglial cells
D Ferrari1, C Stroh, K Schulze-Osthoff
1Department of Internal Medicine I, Medical Clinics, Eberhard-Karls-University, D-72076 Tübingen, Germany.
Abstract:
ATP is released from neurons and other cell types during several physiological and stress conditions under which it exerts various biological effects upon binding to purinoreceptors. A rather peculiar purinoreceptor called P2X7/P2Z is expressed on microglial and other myeloic cells. Although increasing evidence implicates an important role for P2Z in inflammatory processes, little information exists about underlying signaling pathways. Here, we report that in N9 microglial cells, extracellular ATP potently activates nuclear factor of activated T cells (NFAT), a central transcription factor involved in cytokine gene expression. ATP activated NFAT rapidly (within 1 min), whereas activation of nuclear factor kappaB was much delayed, with strikingly distinct kinetics. During ATP stimulation, both NFAT-1 and NFAT-2 were activated by a calcineurin-dependent pathway that required the influx of extracellular calcium ions. Based on the pharmacological profile, NFAT activation was specifically mediated by P2Z and not by other purinoreceptors. N9 cells that lacked P2Z but still expressed P2Y purinoreceptors failed to respond to NFAT activation. We conclude that P2Z-mediated NFAT activation may represent a novel mechanism by which extracellular ATP can modulate early inflammatory gene expression within the nervous and immune system.
Insights
Extracellular ATP rapidly activates the nuclear factor of activated T cells (NFAT) in microglial cells via the P2Z receptor. This calcineurin-dependent pathway, requiring calcium influx, suggests a novel mechanism for ATP in early inflammatory gene expression.
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Extracellular ATP (adenosine triphosphate) influences physiological and stress responses by binding to purinoreceptors.
- The P2X7/P2Z purinoreceptor is found on microglial and myeloid cells and is implicated in inflammation.
- Signaling pathways underlying P2Z receptor function in inflammation remain largely uncharacterized.
Purpose of the Study:
- To investigate the signaling pathways activated by extracellular ATP in microglial cells.
- To determine the role of the P2Z receptor in ATP-induced cellular responses.
- To elucidate the mechanism by which ATP modulates inflammatory gene expression.
Main Methods:
- Utilized N9 microglial cell line for experiments.
- Stimulated cells with extracellular ATP and measured nuclear factor of activated T cells (NFAT) and nuclear factor kappaB (NF-κB) activation.
- Investigated the involvement of calcineurin and extracellular calcium influx in the signaling pathway.
- Employed pharmacological profiling to distinguish between P2Z and other purinoreceptors (e.g., P2Y).
Main Results:
- Extracellular ATP rapidly activated NFAT in N9 microglial cells within 1 minute.
- NFAT activation was dependent on calcineurin and required extracellular calcium influx.
- NF-κB activation exhibited significantly delayed kinetics compared to NFAT.
- NFAT activation was specifically mediated by the P2Z receptor, as cells lacking P2Z did not respond.
Conclusions:
- P2Z receptor activation by extracellular ATP triggers a rapid, calcineurin-dependent NFAT signaling pathway in microglial cells.
- This pathway represents a novel mechanism for extracellular ATP to modulate early inflammatory gene expression.
- The findings highlight a specific role for the P2Z receptor in mediating ATP-induced inflammatory responses in the nervous and immune systems.