Integration of G-protein coupled receptor signaling pathways for activation of a transcription factor (EGR-3).
We recently reported the use of a gene-trapping approach to isolate cell clones in which a reporter gene had integrated into genes modulated by T-cell activation. We have now tested a panel of clones from that report and identified the one that responds to a variety of G-protein coupled receptors (GPCR). The beta-lactamase tagged EGR-3 Jurkat cell was used to dissect specific GPCR signaling in vivo. Three GPCRs were studied, including the chemokine receptor CXCR4 (Gi-coupled) that was endogenously expressed, the platelet activation factor (PAF) receptor (Gq-coupled), and beta2 adrenergic receptor (Gs-coupled) that was both stably transfected. Agonists for each receptor activated transcription of the beta-lactamase tagged EGR-3 gene. Induction of EGR-3 through CXCR4 was blocked by pertussis toxin and PD58059, a specific inhibitor of MEK (MAPK/ERK kinase). Neither of these inhibitors blocked isoproterenol or PAF-mediated activation of EGR-3. Conversely, beta2- and PAF-mediated EGR-3 activation was blocked by the p38, specific inhibitor SB580. In addition, both beta2- and PAF-mediated EGR-3 activation could be synergistically activated by CXCR4 activation. This combined result indicates that EGR-3 can be activated through distinct signal transduction pathways by different GPCRs and that signals can be integrated and amplified to efficiently tune the level of activation.
Tan
Xuehai
X
Beijing Genomics Institute, Beijing 101300, China. tanxh@genomics.org.cn
Sanders
Pam
P
Bolado
Jack
J
Whitney
Mike
M
D003470:Culture Media; D004268:DNA-Binding Proteins / Q000378:metabolism*; D051776:Early Growth Response Protein 3; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D006801:Humans; D019169:Jurkat Cells; D020935:MAP Kinase Signaling System; D019718:Receptors, CXCR4 / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism*; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism*; D001618:beta-Lactamases / Q000378:metabolism
D003470:Culture Media; D004268:DNA-Binding Proteins; D019718:Receptors, CXCR4; D043562:Receptors, G-Protein-Coupled; D014157:Transcription Factors; D051776:Early Growth Response Protein 3; D001618:beta-Lactamases