SIGNAL TRANSDUCTION PATHWAYS IN STABLE PHASE CHRONIC MYELOID LEUKEMIA CELLS

费城的染色体易位产生了嵌合癌基因 Bcr基因和c-abl基因融合在一起。它的产物是 癌基因p210BCR/ABL具有升高的ABL酪氨酸激酶活性，重新定位 到细胞骨架，并使几种细胞蛋白质磷酸化。BCR/ABL 转化造血细胞，诱导因子独立，减少 细胞凋亡，改变CML细胞的黏附能力。然而，在一家生化公司 水平，bcr/abl转化髓系细胞的机制很差。 明白了。已经鉴定了BCR/ABL激酶的几种底物， 包括c-BCR、p120rasGAP、c-CBL、p52SHC、p93FES、p95VAV、p125FAK、 P68paxlin和p72SHPTP2。此外，bcr/abl已被证明可直接结合 在bcr的第177位到Grb2，因此潜在地激活了p21ras。 然而，很难确定其中任何一个的意义 这些潜在的BCR/ABL底物，部分原因是 研究一种具有许多潜在信号基序的大蛋白质。一 简化bcr/abl生物学的方法一直是检查原代人类 CML细胞，而不是高表达bcr/abl的细胞系。 有趣的是，在原代白血病细胞中，只有几种蛋白质 它们被bcr/abl磷酸化。这表明在小学阶段的研究 CML细胞，而不是组织培养细胞系，在 识别重要信号通路的术语。在初步研究中 我们发现只有一种酪氨酸磷酸蛋白与之络合 CML中性粒细胞中的bcr/abl，最近被鉴定为CRKL，一个Sh2/SH3 “适配子”蛋白质。CRKL通过其SH3结构域与BCR/ABL结合。在……里面 进一步的研究，我们已经确定了两种结合到 CML细胞中的CRKL-S2结构域。第一种蛋白质是焦点的一种成分。 第二个是一个130 kDa的蛋白，称为CAS，用于 “CRK相关底物”。在初步研究中，我们克隆了人类 和鸡亭基因，并鉴定了CRKL SH2和CRKL SH2的结合位点 其他蛋白质。这里要检验的中心假设是， BCR/ABL与CRKL接头蛋白的相互作用在 慢性粒细胞白血病稳定期的发病机制。我们的初步数据显示CRKL， 通过与巴西林和或CAS的结合，可能激活了一条途径，该途径 调节整合素的功能、活性或增殖，这些 假说将会得到检验。预计这些结果将 提高对慢性粒细胞白血病发病机制的认识。

The Philadelphia chromosome translocation generates a chimeric oncogene in which the BCR gene and the c-ABL genes are fused. The product of this oncogene, p210BCR/ABL, has elevated ABL tyrosine kinase activity, relocates to the cytoskeleton, and phosphorylates several cellular proteins. BCR/ABL transforms hematopoietic cells, induces factor-independence, reduction of apoptosis, and alters adhesion of CML cells. However, at a biochemical level, the mechanisms by which BCR/ABL transforms myeloid cells are poorly understood. Several substrates of the BCR/ABL kinase have been identified, including c-BCR, p120rasGAP, c-CBL, p52SHC, p93FES, p95VAV, p125FAK, p68paxillin, and p72SHPTP2. Also, BCR/ABL has been shown to bind directly to GRB2 at Y177 of BCR, and therefore potentially activating p21 ras. However, it has been difficult to determine the significance of any of these potential BCR/ABL substrates, in part due to the complexity of studying a large protein with many potential signaling motifs. One approach to simplifying BCR/ABL biology has been to examine primary human CML cells, rather than cell lines made to overexpress BCR/ABL. Interestingly, in primary leukemic cells, there are only a few proteins which are phosphorylated by BCR/ABL. This suggests that studies in primary CML cells, rather than tissue culture cell lines, may be more reliable in terms of identifying important signaling pathways. In preliminary studies we found that there is only a single tyrosine phosphoprotein complexed with BCR/ABL in CML neutrophils, recently identified as CRKL, AN sh2/sh3 "adapter" protein. CRKL binds to BCR/ABL through its SH3 domain. In additional studies, we have identified two cellular proteins which bind to the CRKL S2 domain in CML cells. The first protein is a component of focal adhesions, p68 paxillin, and the second is a 130 kDa protein termed CAS for "CRK associated substrate". In preliminary studies, we cloned the human and chicken pavilion genes, and identified sites for binding CRKL SH2 and other proteins. The central hypothesis to be tested here is that the interaction of BCR/ABL with the CRKL adapter protein is important in the pathogenesis of stable phase CML. Our preliminary data suggest that CRKL, through binding to paxillin and or CAS, may be activating a pathway which regulates integrin function, viability, or proliferation, and these hypotheses will be tested. It is anticipated that these results will improve our understanding of the pathogenesis of CML.