Transcriptional response to calcium-sensing receptor stimulation.
Elevated extracellular Ca(2+) concentrations stimulate the G-protein coupled receptor calcium-sensing receptor. Here we show that this stimulation induces the expression of biologically active early growth response protein 1 (Egr-1), a zinc finger transcription factor. Expression of a dominant-negative mutant of the ternary complex factor Ets-like protein-1 (Elk-1), a key transcriptional regulator of serum response element-driven gene transcription, prevented Egr-1 expression, indicating that Elk-1 or related ternary complex factors connect the intracellular signaling cascade elicited by activation of calcium-sensing receptors with transcription of the Egr-1 gene. These data were corroborated by the fact that stimulation of calcium-sensing receptors increased the transcriptional activation potential of Elk-1. In addition, activator protein-1 (AP-1) transcriptional activity was significantly elevated after the stimulation of calcium-sensing receptors. The expression of a dominant-negative mutant of Elk-1 reduced c-Fos expression and prevented the up-regulation of AP-1 activity as a result of calcium-sensing receptor stimulation, indicating that ternary complex factors control both Egr-1- and AP-1-regulated transcription. In addition, AP-1 activity was reduced after the expression of a dominant-negative mutant of c-Jun in cells expressing an activated calcium-sensing receptor. Stimulus-transcription coupling leading to the up-regulation of Egr-1 and AP-1 controlled transcription in cells expressing calcium-sensing receptors required the protein kinases Raf and ERK, whereas the overexpression of MAPK phosphatase-1 interrupted the signaling cascade connecting calcium-sensing receptor stimulation with transcription of Egr-1 and AP-1 controlled genes. The fact that calcium-sensing receptor stimulation activates the transcription factors Egr-1, Elk-1, and AP-1 indicates that regulation of gene transcription is an integral part of calcium-sensing receptor induced signaling.
Department of Medical Biochemistry and Molecular Biology, University of Saarland Medical Center, D-66421 Homburg, Germany. gerald.thiel@uks.eu
Gerald
G
Thiel
Andrea
A
Lesch
Anja
A
Keim
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D051766:Early Growth Response Protein 1 / Q000096:biosynthesis; D057809:HEK293 Cells; D006801:Humans; D011401:Promoter Regions, Genetic; D044169:Receptors, Calcium-Sensing / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D018808:Transcription Factor AP-1 / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D050807:ets-Domain Protein Elk-1 / Q000235:genetics / Q000378:metabolism
C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; D044169:Receptors, Calcium-Sensing; D018808:Transcription Factor AP-1; D050807:ets-Domain Protein Elk-1; D002118:Calcium