LRG-accelerated differentiation defines unique G-CSFR signaling pathways downstream of PU.1 and C/EBPepsilon that modulate neutrophil activation.
Expression of leucine-rich alpha2 glycoprotein (LRG), a member of the leucine-rich repeat family of proteins, was recently shown to be up-regulated during neutrophil differentiation. Its precise role in granulopoiesis, however, remains unknown. In this paper, we show that the transcription factors PU.1 and C/EBPepsilon that regulate the expression of multiple myeloid-specific genes also bind to the LRG promoter. We also demonstrate that LRG localizes to the same cytoplasmic compartment as myeloperoxidase and that G-CSF treatment of the 32Dcl3 myeloid cell line induces nuclear translocation of LRG. Stable transfection of LRG into 32Dcl3 cells resulted in accelerated, G-CSF-mediated neutrophil differentiation and induction of CD11b expression. In contrast, constitutive expression of LRG in 32Dwt18 cells, expressing a chimeric erythropoietin (Epo)/G-CSFR consisting of the EpoR extracellular domain fused to the G-CSFR transmembrane and cytoplasmic domains, failed to induce accelerated neutrophil differentiation and CD11b expression in response to Epo stimulation. LRG-mediated accelerated differentiation and CD11b expression were found to correlate with an increased level of phospho-Stat3 but not with PU.1 or p27(kip1) levels. Hence, similar to other genes involved in neutrophil differentiation, the expression of LRG also appears to be regulated by PU.1 and C/EBPepsilon. Collectively, these findings suggest a role for LRG in modulating neutrophil differentiation and expression of CD11b via nonredundant G-CSFR signals.
Ai
Jing
J
Davis Heart and Lung Research Institute and Division of Hematology/Oncology, The Ohio State University College of Medicine, Columbus, OH 43210-1240, USA.
Druhan
Lawrence J
LJ
Hunter
Melissa G
MG
Loveland
Megan J
MJ
Avalos
Belinda R
BR
D000818:Animals; D022762:CCAAT-Enhancer-Binding Proteins / Q000502:physiology*; D002454:Cell Differentiation / Q000187:drug effects*; D002458:Cell Fractionation; D002843:Chromatin / Q000648:ultrastructure; D004921:Erythropoietin / Q000494:pharmacology; D005434:Flow Cytometry; D006023:Glycoproteins / Q000235:genetics / Q000502:physiology*; D051379:Mice; D018613:Microscopy, Confocal; D018375:Neutrophil Activation / Q000502:physiology*; D009504:Neutrophils / Q000166:cytology / Q000502:physiology*; D011401:Promoter Regions, Genetic; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D015534:Trans-Activators / Q000502:physiology*; D000099232:Proto-Oncogene Protein Spi-1
D022762:CCAAT-Enhancer-Binding Proteins; D002843:Chromatin; D004921:Erythropoietin; D006023:Glycoproteins; D011518:Proto-Oncogene Proteins; D015534:Trans-Activators; D000099232:Proto-Oncogene Protein Spi-1; C530631:LRG1 protein, mouse