Ho Jenny M-Y, Nguyen Melody H-H, Dierov Jamil K, Badger Karla M, Beattie Bryan K, Tartaro Piero, Haq Rizwan, Zanke Brent W, Carroll Martin P, Barber Dwayne L
Division of Cellular and Molecular Biology, Ontario Cancer Institute, University Health Network, University of Toronto, Ontario, Canada.
Blood. 2002 Aug 15;100(4):1438-48.
The ets transcription factor, TEL, undergoes chromosomal rearrangements with the tyrosine kinase JAK2. TEL-JAK2 is constitutively active, confers cell line factor independence, and activates signal transducer and activator of transcription-1 (STAT1), STAT3, and STAT5. Data from bone marrow transplantation models suggest that STAT5 activation does not account for the entire disease phenotype induced by TEL-JAK2. This study examined additional signaling pathways that are activated by TEL-JAK2. TEL-JAK2 expression in Ba/F3 cells results in constitutive association and tyrosine phosphorylation of Shc and Ship-1 and, consequently, recruitment of Grb2 to TEL-JAK2. Direct Grb2 recruitment is also possible because a putative Grb2 binding site, Tyr314, is present on TEL-JAK2(5-19) and TEL-JAK2(5-12). Studies with a TEL-JAK2(5-19)Tyr314Phe mutant support a role for Tyr314 in Grb2 recruitment, because Grb2 association with TEL-JAK2(5-19)Tyr314Phe is significantly reduced. Interestingly, TEL-JAK2(5-19)Tyr314Phe shows reduced Ras activation when compared with TEL-JAK2(4-17), TEL-JAK2(5-12), and TEL-JAK2(5-19). Analysis of extracellular signal-regulated kinase-1/2 (ERK1/2), stress-activated protein/Jun kinase (SAPK/JNK), and p38 demonstrates the activation of SAPK/JNK and phosphorylation of p38 by all TEL-JAK2 isoforms. TEL-JAK2(5-12) and TEL-JAK2(5-19) preferentially phosphorylate ERK2, whereas TEL-JAK2(4-17) phosphorylated ERK2 at lower levels. Inhibition studies demonstrated that ERK1/2 activation was necessary for Ba/F3 factor independence mediated by TEL-JAK2(5-19), while inhibition of SAPK/JNK or p38 activity had no effect. Our data reveal the requirement of ERK activation by TEL-JAK2(5-19) in Ba/F3 cells and suggest that TEL-JAK2 leukemogenic potential may be mediated in part through ERK1/2.
ets转录因子TEL与酪氨酸激酶JAK2发生染色体重排。TEL-JAK2组成性激活，赋予细胞系因子非依赖性，并激活信号转导及转录激活因子1（STAT1）、STAT3和STAT5。骨髓移植模型的数据表明，STAT5激活并不能解释TEL-JAK2诱导的整个疾病表型。本研究检测了由TEL-JAK2激活的其他信号通路。Ba/F3细胞中TEL-JAK2的表达导致Shc和Ship-1的组成性结合及酪氨酸磷酸化，进而导致Grb2募集至TEL-JAK2。直接募集Grb2也是可能的，因为在TEL-JAK2(5-19)和TEL-JAK2(5-12)上存在一个假定的Grb2结合位点Tyr314。对TEL-JAK2(5-19)Tyr314Phe突变体的研究支持Tyr314在Grb2募集中的作用，因为Grb2与TEL-JAK2(5-19)Tyr314Phe的结合显著减少。有趣的是，与TEL-JAK2(4-17)、TEL-JAK2(5-12)和TEL-JAK2(5-19)相比，TEL-JAK2(5-19)Tyr314Phe显示出Ras激活减少。对细胞外信号调节激酶1/2（ERK1/2）、应激激活蛋白/Jun激酶（SAPK/JNK）和p38的分析表明，所有TEL-JAK2亚型均能激活SAPK/JNK并使p38磷酸化。TEL-JAK2(5-12)和TEL-JAK2(5-19)优先磷酸化ERK2，而TEL-JAK2(4-17)对ERK2的磷酸化水平较低。抑制研究表明，ERK1/2激活对于TEL-JAK2(5-19)介导的Ba/F3细胞因子非依赖性是必需的，而抑制SAPK/JNK或p38活性则没有影响。我们的数据揭示了Ba/F3细胞中TEL-JAK2(5-19)激活ERK的必要性，并表明TEL-JAK2的白血病致癌潜能可能部分通过ERK1/2介导。
