Growth and Differentiation through the Cytokine Receptors

促红细胞生成素（EPO）与其膜受体的相互作用可诱导红系祖细胞的增殖和分化。EPO已显示在各种造血细胞系中激活JAK 2-STAT 5途径，尽管该途径的生理作用尚不清楚。我们在嵌合受体的胞质结构域中引入了各种缺失和酪氨酸（Y）取代苯丙氨酸（F），并在EPO应答性红白血病细胞系ELM-I-1中表达了这些突变嵌合体。我们发现EPO受体的Y343或Y 401是红系分化和STAT 5激活所必需的。我们寻找了立即早期细胞因子应答基因，并分离出一种新的基因，CIS（含细胞因子诱导SH 2蛋白），其通过STAT 5诱导。我们克隆了CIS基因的5 '侧翼区，发现转录起始位点上游约200个碱基含有四个潜在的START 5结合位点（MGF盒）。CIS含有SH 2结构域并结合酪氨酸磷酸化的EPO和IL 3受体。CIS是STAT 5的反馈调节剂;其表达由STAT 5诱导，并且其通过结合受体来负性调节STAT 5活化。我们目前正在通过创建转基因和基因敲除小鼠来研究CIS的功能。我们还发现了一个新的CIS相关分子JAB，以JAK 2酪氨酸激酶结构域为诱饵，利用酵母双杂交技术克隆了JAB。JAB是JAK激酶的负调节因子，可能抑制细胞因子的多种作用。我们正在研究联合申诉委员会的职能。

Interaction between erythropoietin (EPO) and its membrane receptor induces the proliferation and differentiation of erythroid progenitors. EPO has been shown to activate the JAK2-STAT5 pathway in various hematopoietic cell lines, although the physiological role of this pathway is unclear. We introduced various deletion and tyrosine (Y) to phenylalanine (F) substitution in the cytoplasmic domain of the chimeric receptor and expressed these mutant chimeras in an EPO-responsive erythroleukemia cell line, ELM-I-1. We found that Y343 or Y401 of the EPO receptor are independently necessary for erythroid differentiation as well as STAT5 activation. We searched for immediate early cytokine responsive genes and isolated a novel gene, CIS (Cytokine Inducible SH2 containing protein) that is induced through STAT5. We cloned the 5'-flanking region of the CIS gene, and found that about 200 bases upstream of the transcription-initiation site contain four potential START5 binding sites (MGF boxes). CIS contains an SH2 domain and binds to tyrosine-phosphorylated EPO and IL3 receptors. CIS is a feedback modulator of STAT5 ; its expression is induced by STAT5 and it negatively modulates STAT5 activation by binding to the receoptor. We are currently investigating the function of CIS by creating transgenic and knockout mice. We also found a novel CIS related molecule, JAB,JAB was cloned by yeast two-hybrid using JAK2 tyrosine kinase domain as bait. JAB is a negative regulator of JAK kinases ans probably inhibits various action of cytokines. We are studying the function of JAB.