Calcium Influx via the NMDA Receptor Induces Immediate Early Gene Transcription by a MAP Kinase/ERK-Dependent Mechanism

Abstract

The regulation of gene expression by neurotransmitters is likely to play a key role in neuroplasticity both during development and in the adult animal. Therefore, it is important to determine the mechanisms of neuronal gene regulation to understand fully the mechanisms of learning, memory, and other long-term adaptive changes in neurons. The neurotransmitter glutamate stimulates rapid and transient induction of many genes, including the c-fos proto-oncogene. The c-fos promoter contains several critical regulatory elements, including the serum response element (SRE), that mediate glutamate-induced transcription in neurons; however, the mechanism by which the SRE functions in neurons has not been defined. In this study, we sought to identify transcription factors that mediate glutamate induction of transcription through the SRE in cortical neurons and to elucidate the mechanism(s) of transcriptional activation by these factors. To facilitate this analysis, we developed an improved calcium phosphate coprecipitation procedure to transiently introduce DNA into primary neurons, both efficiently and consistently. Using this protocol, we demonstrate that the transcription factors serum response factor (SRF) and Elk-1 can mediate glutamate induction of transcription through the SRE in cortical neurons. There are at least two distinct pathways by which glutamate signals through the SRE: an SRF-dependent pathway that can operate in the absence of Elk and an Elk-dependent pathway. Activation of the Elkdependent pathway of transcription seems to require phosphorylation of Elk-1 by extracellular signal-regulated kinases (ERKs), providing evidence for a physiological function of ERKs in glutamate signaling in neurons. Taken together, these findings suggest that SRF, Elk, and ERKs may have important roles in neuroplasticity.

Dynamic interaction between medial prefrontal cortex and nucleus accumbens as a function of both motivational state and reinforcer magnitude: A c-Fos immunocytochemistry study

“…In this situation, one would predict that higher activity in the mPFC should result in higher activity levels (and c-Fos immunoreactivity) in the NAcc -thereby rendering a strong positive correlation in the c-Fos counts of the two regions. Consistent with this idea are reports that glutamate can induce c-Fos in the striatum (Vanhoutte et al, 1999;Xia et al, 1996). Thus, it seems that under certain conditions the mPFC can inhibit the activity of the NAcc (possibly by inhibiting NAcc DA release), while under other conditions, and possibly via different cell populations, the mPFC can excite the NAcc.…”

Striatal proenkephalin gene induction: coordinated regulation by cyclic AMP and calcium pathways

“…No differences in gene regulation pattern have been observed between pENKAT12 and longer constructs, however, pENKAT12 was most responsive [14]. Enkephalin constructs were transfected into primary striatal cultures using Ca 2+ transfection [25], as described previously [18]. RNA was extracted and analyzed as described previously [18].…”

The PDZ-binding domain is essential for the dendritic targeting of 5-HT2A serotonin receptors in cortical pyramidal neurons in vitro

“…Optimal efficiency of infection for immunofluorescent studies (approximately 5-10% infection) was reached by diluting the viral supernatant in a 1:5 ratio and then incubating for 12-16 h. For each construct, SFV-mediated transient expression was performed for at least three times. Neurons were also transfected with 2A-GFP-CT and 2A-GFP using a calcium phosphate-mediated protocol (Xia et al, 1996) for comparison with the viral method. In our hands, we were able to achieve less than 0.1% transfection efficiency using the calcium phosphate-mediated method.…”