Many patients with chronic myeloid leukemia in deep remission experience return of clinical disease after withdrawal of tyrosine kinase inhibitors (TKIs). This suggests signaling of inactive BCR–ABL, which allows the survival of cancer cells, and relapse. We show that TKI treatment inhibits catalytic activity of BCR–ABL, but does not dissolve BCR–ABL core signaling complex, consisting of CRKL, SHC1, GRB2, SOS1, cCBL, p85a-PI3K, STS1 and SHIP2. Peptide microarray and co-immunoprecipitation results demonstrate that CRKL binds to proline-rich regions located in C-terminal, intrinsically disordered region of BCR–ABL, that SHC1 requires pleckstrin homology, src homology and tyrosine kinase domains of BCR–ABL for binding, and that BCR–ABL sequence motif located in disordered region around phosphorylated tyrosine 177 mediates binding of three core complex members, i.e., GRB2, SOS1, and cCBL. Further, SHIP2 binds to the src homology and tyrosine kinase domains of BCR–ABL and its inositol phosphatase activity contributes to BCR–ABL-mediated phosphorylation of SHC1. Together, this study characterizes protein–protein interactions within the BCR–ABL core complex and determines the contribution of particular BCR–ABL domains to downstream signaling. Understanding the structure and dynamics of BCR–ABL interactome is critical for the development of drugs targeting integrity of the BCR–ABL core complex.

许多深度缓解的慢性粒细胞白血病患者在停用酪氨酸激酶抑制剂 (TKI) 后，临床疾病复发。这表明 BCR-ABL 信号不活跃，可以使癌细胞存活并复发。我们发现 TKI 处理抑制 BCR-ABL 的催化活性，但不会溶解 BCR-ABL 核心信号复合物，该复合物由 CRKL、SHC1、GRB2、SOS1、cCBL、p85a-PI3K、STS1 和 SHIP2 组成。肽微阵列和免疫共沉淀结果表明，CRKL 与位于 BCR-ABL C 末端、本质上无序区域的富含脯氨酸的区域结合，SHC1 需要 BCR-ABL 的 pleckstrin 同源性、src 同源性和酪氨酸激酶结构域进行结合，并且位于磷酸化酪氨酸177周围无序区域的BCR-ABL序列基序介导三个核心复合体成员（即GRB2、SOS1和cCBL）的结合。此外，SHIP2 与 BCR-ABL 的 src 同源性和酪氨酸激酶结构域结合，其肌醇磷酸酶活性有助于 BCR-ABL 介导的 SHC1 磷酸化。总之，这项研究描述了 BCR-ABL 核心复合物内蛋白质-蛋白质相互作用的特征，并确定了特定 BCR-ABL 结构域对下游信号传导的贡献。了解 BCR-ABL 相互作用组的结构和动态对于开发针对 BCR-ABL 核心复合物完整性的药物至关重要。