ten Hoeve J, Arlinghaus R B, Guo J Q, Heisterkamp N, Groffen J
Department of Pathology, Childrens Hospital of Los Angeles.
Blood. 1994 Sep 15;84(6):1731-6.
The chimeric BCR/ABL protein is characteristic of Philadelphia (Ph)+ leukemia because it is the direct product of the Ph translocation and it has been shown to play a causal role in the genesis of leukemia. The BCR/ABL protein exhibits a deregulated tyrosine-kinase activity capable of phosphorylating different cellular substrates in vivo and in vitro. CRKL, an adaptor protein consisting of SH2 and SH3 domains in the absence of a catalytic domain, is one potential in vivo substrate of BCR/ABL. Previous experiments have shown that CRKL is phosphorylated on tyrosine in the chronic myelogenous leukemia (CML) cell line K562 and that CRKL is a substrate for ABL and for BCR/ABL in COS-1 cells. In the current study, we show that in peripheral blood cells a direct correlation exists between the presence of BCR/ABL and the phosphorylation status of CRKL. In Ph- peripheral blood cells, CRKL is present only in the nonphosphorylated form. In contrast, all BCR/ABL+ CML and acute lymphoblastic leukemia patient samples examined showed clear tyrosine-phosphorylation of CRKL. This result strongly suggests that CRKL is a biologically significant substrate for BCR/ABL and is likely to play a major role in the development of Ph+ leukemia.
嵌合型BCR/ABL蛋白是费城染色体（Ph）阳性白血病的特征性蛋白，因为它是Ph染色体易位的直接产物，并且已被证明在白血病的发生中起因果作用。BCR/ABL蛋白表现出失调的酪氨酸激酶活性，能够在体内和体外磷酸化不同的细胞底物。CRKL是一种衔接蛋白，在缺乏催化结构域的情况下由SH2和SH3结构域组成，是BCR/ABL在体内的一个潜在底物。先前的实验表明，CRKL在慢性粒细胞白血病（CML）细胞系K562中发生酪氨酸磷酸化，并且在COS-1细胞中CRKL是ABL和BCR/ABL的底物。在本研究中，我们表明在外周血细胞中，BCR/ABL的存在与CRKL的磷酸化状态之间存在直接相关性。在Ph阴性外周血细胞中，CRKL仅以非磷酸化形式存在。相反，所有检测的BCR/ABL阳性CML和急性淋巴细胞白血病患者样本均显示CRKL有明显的酪氨酸磷酸化。这一结果强烈表明，CRKL是BCR/ABL具有生物学意义的底物，并且可能在Ph阳性白血病的发展中起主要作用。
