Tauchi T, Yoshimura A, Ohyashiki K
First Department of Internal Medicine, Tokyo Medical University, Tokyo, Japan.
Exp Hematol. 2001 Mar;29(3):356-61. doi: 10.1016/s0301-472x(00)00673-1.
BCR/ABL is a chimeric oncoprotein that exhibits deregulated tyrosine kinase activity and is implicated in the pathogenesis of Philadelphia chromosome (Ph)-positive leukemia. A general understanding of BCR/ABL signaling events is emerging, but little is known about the endogenous inhibitors of p210 BCR/ABL. The present study focused attention on CIS1, a cytokine-inducible SH2 protein, as a potential physiologic antagonist for BCR/ABL.
The murine hematopoietic cell line NSF/N1.H7 stably transfected with BCR/ABL was compared to the parental counterparts for induction of CIS1 by immunoblotting and immunoprecipitation. Cells were treated with a proteasome inhibitor to examine the effect of a proteasome inhibitor on CIS1 protein expression. To determine the effect of CIS1 on BCR/ABL-mediated transformation, we generated Rat-1 fibroblasts transfected with either a control vector, CIS1, BCR/ABL p210, or CIS1 plus BCR/ABL p210.
Three forms of CIS1 with molecular masses of 32, 37, and 47 kDa were detected in BCR/ABL-transformed cells. The 47-kDa protein was a ubiquitinated protein. The proteasome inhibitor increased the formation of complexes between CIS1 and BCR/ABL. Transformation of p210 BCR/ABL was significantly suppressed in cells overexpressing CIS1.
The results suggest that CIS1 is an endogenous inhibitor of p210 BCR/ABL and is likely to be important in the pathogenesis of Ph-positive leukemia.
BCR/ABL是一种嵌合癌蛋白，具有失调的酪氨酸激酶活性，与费城染色体（Ph）阳性白血病的发病机制有关。目前对BCR/ABL信号转导事件已有大致了解，但对p210 BCR/ABL的内源性抑制剂知之甚少。本研究聚焦于细胞因子诱导的SH2蛋白CIS1，将其作为BCR/ABL的潜在生理拮抗剂。
通过免疫印迹和免疫沉淀法，比较稳定转染BCR/ABL的小鼠造血细胞系NSF/N1.H7与其亲本细胞系中CIS1的诱导情况。用蛋白酶体抑制剂处理细胞，以检测蛋白酶体抑制剂对CIS1蛋白表达的影响。为确定CIS1对BCR/ABL介导的转化的影响，我们构建了转染对照载体、CIS1、BCR/ABL p210或CIS1加BCR/ABL p210的大鼠-1成纤维细胞。
在BCR/ABL转化的细胞中检测到三种分子量分别为32、37和47 kDa的CIS1形式。47 kDa的蛋白是一种泛素化蛋白。蛋白酶体抑制剂增加了CIS1与BCR/ABL之间复合物的形成。在过表达CIS1的细胞中，p210 BCR/ABL介导的转化受到显著抑制。
结果表明CIS1是p210 BCR/ABL的内源性抑制剂，可能在Ph阳性白血病的发病机制中起重要作用。
