Mature human neutrophils constitutively express the transcription factor EGR-1.
The immediate early response gene, Early Growth Response 1 (EGR-1) has emerged as a central regulator of early inflammatory and immune processes by rapidly regulating the transcription of a wide array of downstream effector genes. Neutrophils, which are among the first circulating leukocytes to respond to inflammatory signals, exhibit a broad set of transcriptional changes immediately upon exposure to inflammatory and pathogenic stimuli. Such transcriptional changes are likely to be controlled by early gene transcription factors such as EGR-1. We therefore examined the regulation and role of EGR-1 in mature human neutrophils exposed to the inflammatory stimuli fMLP and IL-8. We report that human neutrophils rapidly and transiently up-regulate EGR-1 mRNA upon stimulation with fMLP or IL-8. However in contrast to that seen in other cells, EGR-1 mRNA expression profiles were not predictive of protein expression. Instead, we show that human neutrophils constitutively express EGR-1 protein. The cellular content of EGR-1 did not change over time or upon neutrophil activation. Confocal microscopy revealed that EGR-1 was present in both the cytoplasm and nuclei of un-stimulated neutrophils and that activation did not change this subcellular localization or promote nuclear translocation. Using chromatin immunoprecipitation, we demonstrate that EGR-1 is associated with the promoter regions of the immune regulatory genes IL-1 beta, TGFbeta-1 and MIF in both resting and activated neutrophils with increased promoter association observed upon cell activation. This novel pattern of EGR-1 protein expression may underlie the ability of the neutrophil to respond rapidly to inflammatory stimuli.
Cullen
Eva M
EM
UCD Conway Institute, UCD School of Medicine and Medical Science, University College Dublin, Belfield, Dublin 4, Ireland. eva.cullen@ucd.ie
Brazil
Jennifer C
JC
O'Connor
Clare M
CM
D015153:Blotting, Western; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D047369:Chromatin Immunoprecipitation; D003593:Cytoplasm / Q000378:metabolism; D051766:Early Growth Response Protein 1 / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects / Q000235:genetics*; D020869:Gene Expression Profiling; D006801:Humans; D053583:Interleukin-1beta / Q000235:genetics; D016209:Interleukin-8 / Q000494:pharmacology; D018613:Microscopy, Confocal; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D018375:Neutrophil Activation; D009504:Neutrophils / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D020133:Reverse Transcriptase Polymerase Chain Reaction; D053773:Transforming Growth Factor beta1 / Q000235:genetics
C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; D053583:Interleukin-1beta; D016209:Interleukin-8; D053773:Transforming Growth Factor beta1; D009240:N-Formylmethionine Leucyl-Phenylalanine