LRG-accelerated differentiation defines unique G-CSFR signaling pathways downstream of PU.1 and C/EBPε that modulate neutrophil activation
LRG-accelerated differentiation defines unique G-CSFR signaling pathways downstream of PU.1 and C/EBPε that modulate neutrophil activation
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DOI：
10.1189/jlb.1107751
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发表时间：
2008-05-01
影响因子：
5.5
通讯作者：
Avalos, Belinda R.
中科院分区：
文献类型：
--
作者：
Ai, Jing;Druhan, Lawrence J.;Avalos, Belinda R.
富含亮氨酸的α2糖蛋白(LRG)是富含亮氨酸的重复蛋白家族中的一员，近年来发现其在中性粒细胞分化过程中表达上调。然而，它在粒细胞生成中的确切作用仍不清楚。在这篇文章中，我们证明了调控多个髓系特异基因表达的转录因子PU.1和C/EBP epsilon也与LRG启动子结合。我们还证明了LRG定位于与髓过氧化物酶相同的细胞质隔室，并且G-CSF处理32Dcl3髓系细胞系诱导了LRG的核移位。稳定地将LRG导入32Dcl3细胞，可加速G-CSF介导的中性粒细胞分化，并诱导CD11b表达。相反，LRG在32Dwt18细胞中的组成性表达，表达了融合了EPOR胞外区和G-CSFR跨膜区和胞内区的EPO/G-CSFR，但未能诱导中性粒细胞加速分化和CD11b表达。LRG介导的加速分化和CD11b的表达与磷酸化STAT3水平的升高有关，而与PU.1或p27(Kip1)的水平无关。因此，与其他涉及中性粒细胞分化的基因一样，LRG的表达似乎也受到PU.1和C/EBP epsilon的调控。总之，这些发现提示LRG通过非冗余G-CSFR信号调节中性粒细胞分化和CD11b的表达。
Expression of leucine-rich alpha 2 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/EBP epsilon 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/EBP epsilon. Collectively, these findings suggest a role for LRG in modulating neutrophil differentiation and expression of CD11b via nonredundant G-CSFR signals.