Related Experiment Videos
Ionotropic glutamate receptor subtypes activate c-fos transcription by distinct calcium-requiring intracellular
1Department of Medicine, Veterans Administration Medical Center, Durham, North Carolina.
Abstract:
N-Methyl-D-aspartate (NMDA) or non-NMDA receptor activation is sufficient to induce transcription of the immediate early gene c-fos in a calcium-requiring manner. We sought to determine whether the calcium-dependent mechanisms inducing c-fos transcription are identical following activation of these two receptor subtypes. We used in situ hybridization and fura-2 imaging to detect c-fos mRNA and intracellular calcium in individual dentate gyrus neurons maintained in vitro. Structurally distinct inhibitors of phospholipase A2 and cyclooxygenase abolished NMDA--but not kainic acid-induced increases of c-fos mRNA. Conversely, the calmodulin antagonist calmidazolium markedly inhibited kainic acid--but not NMDA-mediated increases of c-fos mRNA. We propose that the dissociation in the mechanisms transducing the calcium influx signals to the nucleus following NMDA and non-NMDA receptor activation is due to spatially distinct sites of calcium entry, resulting in activation of different enzymes located at distinct sites in the cell.
Insights
N-Methyl-D-aspartate (NMDA) and non-NMDA receptor activation trigger c-fos gene transcription via distinct calcium-dependent pathways. These differences in signaling mechanisms are linked to specific calcium entry sites within neurons.
Area of Science:
- Neuroscience
- Molecular Biology
- Cell Signaling
Background:
- N-Methyl-D-aspartate (NMDA) and non-NMDA receptors mediate excitatory neurotransmission.
- Receptor activation induces immediate early gene c-fos transcription, a process dependent on intracellular calcium.
- The precise calcium-dependent signaling cascades downstream of NMDA and non-NMDA receptors remain incompletely understood.
Purpose of the Study:
- To investigate whether the intracellular calcium-dependent mechanisms that induce c-fos transcription are identical following activation of NMDA and non-NMDA receptor subtypes.
- To elucidate the distinct molecular pathways involved in transducing calcium signals to the nucleus after activation of different glutamate receptor types.
Main Methods:
- In situ hybridization was employed to detect c-fos messenger RNA (mRNA) levels in individual neurons.
- Fura-2 imaging was utilized to measure intracellular calcium concentrations in real-time.
- Specific enzyme inhibitors (phospholipase A2, cyclooxygenase) and a calmodulin antagonist (calmidazolium) were used to probe signaling pathways.
Main Results:
- NMDA receptor activation-induced c-fos mRNA increases were abolished by phospholipase A2 and cyclooxygenase inhibitors.
- Kainic acid (a non-NMDA receptor agonist)-induced c-fos mRNA increases were significantly inhibited by the calmodulin antagonist calmidazolium.
- NMDA receptor activation-induced increases were unaffected by calmidazolium, while kainic acid-induced increases were unaffected by phospholipase A2 and cyclooxygenase inhibitors.
Conclusions:
- The mechanisms transducing calcium influx signals to the nucleus differ between NMDA and non-NMDA receptor activation.
- These differences are likely due to spatially distinct sites of calcium entry.
- Distinct calcium entry sites lead to the activation of different enzymes at specific cellular locations, thereby modulating c-fos transcription.