Action Potential-Dependent Regulation of Gene Expression: Temporal Specificity in Ca2+, cAMP-Responsive Element Binding Proteins, and Mitogen-Activated Protein Kinase Signaling

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Abstract
Specific patterns of neural impulses regulate genes controlling nervous system development and plasticity, but it is not known how intracellular signaling cascades and transcriptional activation mechanisms can regulate specific genes in response to specific patterns of action potentials. Studies using electrical stimulation of mouse dorsal root ganglion neurons in culture show that the temporal dynamics of intracellular signaling pathways are an important factor. Expression ofc-fosvaried inversely with the interval between repeated bursts of action potentials. Transcription was not dependent on a large or sustained increase in intracellular Ca2+, and high Ca2+levels separated by long interburst intervals (5 min) produced minimal increases inc-fosexpression. Levels of the transcription factor cAMP-responsive element binding protein (CREB), phosphorylated at Ser-133, increased rapidly in response to brief action potential stimulation but remained at high levels several minutes after an action potential burst. These kinetics limited the fidelity with which P-CREB could follow different patterns of action potentials, and P-CREB levels were not well correlated withc-fosexpression. The extracellular-regulated kinase (ERK) mitogen-activated protein kinases (MAPK) also were stimulated by action potentials of appropriate temporal patterns. Bursts of action potentials separated by long intervals (5 min) did not activate MAPK effectively, but they did increase CREB phosphorylation. This was a consequence of the more rapid dephosphorylation of MAPK in comparison to CREB. High expression ofc-foswas dependent on the combined activation of the MAPK pathway and phosphorylation of CREB. These observations show that temporal features of action potentials (and associated Ca2+transients) regulate expression of neuronal genes by activating specific intracellular signaling pathways with appropriate temporal dynamics.