Role of Ab1 Kinases in B and T cell signaling

描述(由申请人提供)：Abl酪氨酸激酶参与调节细胞的增殖、存活、黏附和迁移。C-Abl在小鼠体内的靶向缺失揭示了该蛋白在B和T细胞发育和功能中的作用。C-Abl基因缺陷小鼠表现出脾、胸腺萎缩和淋巴细胞减少，从c-Abl基因敲除小鼠分离的B淋巴细胞在生长因子停用后增加了对细胞凋亡的易感性。我们已经证明，c-Abl基因敲除小鼠的脾B细胞对B细胞受体(BCR)刺激的增殖反应减弱，并且c-Abl结合并磷酸化BCR共同受体CD19。C-Abl激酶在小鼠发育过程中表现出与Arg的功能冗余，Arg是一种Abl相关的酪氨酸激酶。C-Abl或Arg的单一缺失会产生存活的小鼠，但这两种激酶的纯合缺失会导致胚胎死亡，胚胎会出现细胞骨架异常和多个组织中的细胞凋亡。Arg酪氨酸激酶在胸腺和脾组织中高度表达，可以弥补c-Abl在这些组织中的丢失。我们最近的研究发现，抑制T细胞中Abl激酶的活性显著抑制T细胞受体(TCR)依赖的增殖、IL-2的产生、IL-2启动子的转录以及TCR信号关键蛋白的酪氨酸磷酸化，从而进一步支持Abl激酶在淋巴细胞信号转导中的作用。我们假设Abl家族的激酶调节B和T细胞免疫受体下游的增殖、存活和细胞骨架反应。有两个特定的目的被提出：1)确定Abl激酶用于调控TCR参与下游的增殖、存活、细胞骨架重组和整合素介导的黏附的机制，并确定这些过程中的关键Abl靶点；2)确定c-Abl通过识别关键的Abl靶点和上游调节因子来调节对BCR刺激的增殖反应的机制，以及研究Arg的丢失是否加剧了c-Abl依赖的B细胞表型。本实验的结果将从机制上解释Abl激酶丢失导致的小鼠B细胞和T细胞表型缺陷，并揭示在正常淋巴细胞中受这些激酶调控的新的信号通路，以及在Abl激酶功能丧失或解除调节所引发的病理条件下。

DESCRIPTION (provided by applicant): The Abl tyrosine kinases have been implicated in the regulation of cell proliferation, survival, adhesion, and migration. Targeted deletion of c-Abl in mice has revealed a role for this protein in B and T cell development and function. The c-Abl-deficient mice exhibit splenic and thymic atrophy and lymphopenia, and B lymphocytes isolated from c-Abl knockout mice have increased susceptibility to apoptosis following growth factor withdrawal. We have shown that splenic B cells from c-Abl knockout mice exhibit a reduced proliferative response to B cell receptor (BCR) stimulation, and that c-Abl binds to and phosphorylates the BCR co-receptor CD19. The c-Abl kinase exhibits functional redundancy during mouse development with Arg, an Abl-related tyrosine kinase. Single loss of c-Abl or Arg produces viable mice, but homozygous loss of both kinases results in embryonic lethality with the embryos displaying cytoskeletal abnormalities and apoptosis in multiple tissues. The Arg tyrosine kinase is highly expressed in thymus and spleen, and may compensate for loss of c-Abl in these tissues. A role for Abl kinases in lymphocyte signaling is further supported by our recent finding that inhibiting the activities of the Abl kinases in T cells markedly inhibits T cell receptor (TCR)-dependent proliferation, IL-2 production, transcription of the IL-2 promoter, and tyrosine phosphorylation of a subset of proteins critical for TCR signaling. We hypothesize that Abl family kinases regulate proliferative, survival, and cytoskeletal responses downstream of immunoreceptors in B and T cells. Two specific aims are proposed: 1) to define the mechanisms employed by the Abl kinases to regulate proliferation, survival, cytoskeletal reorganization, and integrin-mediated adhesion downstream of TCR engagement, and identify the critical Abl targets in these processes, and 2) to define the mechanisms whereby c-Abl regulates the proliferative response to BCR stimulation through identification of critical Abl targets and upstream regulators, as well as to examine whether loss of Arg exacerbates the c-Abl dependent B cell phenotypes. Results from the proposed experiments will provide mechanistic explanations for the defective B and T cell phenotypes induced by loss of Abl kinases in mice, and wilt reveal novel signaling pathways modulated by these kinases in normal lymphocytes and under pathological conditions elicited by loss or deregulation of Abl kinase function.