Intracellular signaling mechanisms in normal human hematopoietic progenitors and mature leukocytes

1.细胞因子对中性粒细胞肌动蛋白重组和运动的调节：G-CSF、GM-CSF和肿瘤坏死因子-α刺激中性粒细胞可引起肌动蛋白解聚和形态改变。最大反应出现在20min内。我们发现ERK和p38MAPK的激活在这些细胞因子诱导的肌动蛋白重组和形态改变中起着关键作用。G-CSF还可诱导中性粒细胞随机迁移，并受ERK和P13K的调节。2.G-CSF对人单核细胞功能的调节：在G-CSF刺激的单核细胞中，STAT3被选择性地激活。我们发现G-CSF通过激活STAT3抑制脂多糖诱导的单核细胞产生肿瘤坏死因子-α。G-CSF在体内观察到的免疫调节作用可能部分归因于G-CSF对单核细胞功能的直接作用。3.人中性粒细胞存活和cIAP2：人中性粒细胞表达凋亡抑制因子(IAP)家族成员，即cIAP1、cIAP2和XIAP。在这些成员中，在体外和体内，G-CSF刺激选择性上调了cIAP2的表达。通过激活JAK2-STAT3通路上调cIAP2的表达。CIAP2蛋白表达增加可能与G-CSF介导的中性粒细胞抗凋亡作用有关。此外，我们还发现慢性中性粒细胞白血病患者的成熟中性粒细胞明显过度表达cIAP2mRNA，存活时间延长。4.STAT3亚型在人中性粒细胞中的表达：据报道，STAT3STAT3γ是人中性粒细胞中主要的STAT3亚型。我们发现，与以前的报道相反，STAT3α主要在人中性粒细胞中表达，而不是STAT3γ。在用常规裂解缓冲液制备中性粒细胞裂解物的过程中，STAT3γ是由STAT3α通过颗粒衍生的丝氨酸蛋白酶有限降解而迅速产生的。

1.Regulation of actin reorganization and motility in human neutrophils by cytokines : Stimulation of neutrophils with G-CSF, GM-CSF or TNF-α resulted in actin de polymerization and morphological change. The maximum responses were detected within 20 min. We found that activation of ERK and p38 MAPK plays a critical role in actin reorganization and morphological change induced by these cytokines. G-CSF also induced random migration in neutrophils, and G-CSF-induced neutrophil migration was regulated by ERK and P13K.2.Regulation of human monocyte functions by G-CSF : Among the signaling molecules, STAT3 was selectively activated in monocytes stimulated by G-CSF. We found that G-CSF inhibited LPS-induced TNF-α production in monocytes through activation of STAT3. The immunomodulation observed in vivo by G-CSF administration may be partly ascribed to the direct effect of G-CSF on monocyte functions.3.Human neutrophil survival and cIAP2 : Human neutrophils were found to express members of the inhibitor of apoptosis (IAP) family, namely cIAP1, cIAP2 and XIAP. Among these members, cIAP2 expression was selectively up-regulated by G-CSF stimulation in vitro and in vivo. Up-regulation of cIAP2 expression was mediated by activation of the JAK2-STAT3 pathway. Increased expression of cIAP2 protein may contribute to G-CSF-mediated anti-apoptotic effect on neutrophils. In addition, we found that mature neutrophils from a patient with chronic neutrophilic leukemia exhibited remarkable over-expression of cIAP2 mRNA and prolongation of survival.4.STAT3 isoforms expressed in human neutrophils : It has been reported that STAT3γ is a major STAT3 isoform in human neutrophils. We found that, in contrast to the previous reports, STAT3α, but not STAT3γ, was primarily expressed in human neutrophils, and STAT3γ was rapidly generated from STAT3α by limited proteolysis with granule-derived serine proteases during preparation of neutrophil lysates with the conventional lysis buffer.