CrkL activates integrin-mediated hematopoietic cell adhesion through the guanine nucleotide exchange factor C3G
CrkL activates integrin-mediated hematopoietic cell adhesion through the guanine nucleotide exchange factor C3G
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DOI：
10.1182/blood.v93.11.3713.411a36_3713_3722
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发表时间：
1999-06-01
期刊：
影响因子：
20.3
通讯作者：
Miura, O
中科院分区：
文献类型：
--
作者：
Arai, A;Nosaka, Y;Miura, O
CrkL 是主要由 SH2 和 SH3 结构域组成的接头蛋白 Crk 家族的成员，CrkL 在造血细胞中表达最丰富，并且与慢性粒细胞白血病的发病机制有关。然而，其功能尚未明确定义。在这里，我们发现 CrkL 的过度表达增强了造血 32D 细胞对纤连蛋白的粘附。 CrkL 诱导的细胞粘附增加被针对 VLA-4 (α 4 beta 1) 和 VLA-5 ((α 5 beta 1) 的抗体阻断，但观察到这些整联蛋白的表面表达水平没有变化。使用 CrkL 突变体的研究表明，SH2 结构域是增强细胞粘附的部分必需，而 C 端 SH3 结构域以及酪氨酸磷酸化位点 (Y207) 是可有可无的。相反，N 端SH3结构域参与结合C3G和其他信号分子，被证明起着至关重要的作用，因为该结构域的缺陷对细胞与纤连蛋白的粘附显示出抑制作用。此外，C3G的过度表达也增加了造血细胞与纤连蛋白的粘附，而缺乏鸟嘌呤核苷酸交换结构域的C3G突变体消除了CrkL诱导的细胞粘附增加。 Raf-1 增强了基础和 CrkL 诱导的细胞粘附，而 R-Ras 则适度降低了粘附，这些结果表明，CrkL-C3G 复合物可能通过 C3G 的鸟嘌呤核苷酸交换活性激活造血细胞中的 VLA-4 和 VLA-5，包括 R-Ras (C) 1999。
CrkL is a member of the Crk family of adapter proteins consisting mostly of SH2 and SH3 domains, CrkL is most abundantly expressed in hematopoietic cells and has been implicated in pathogenesis of chronic myelogenous leukemia. However, its function has not been precisely defined. Here, we show that overexpression of CrkL enhances the adhesion of hematopoietic 32D cells to fibronectin. The CrkL-induced increase in cell adhesion was blocked by antibodies against VLA-4 (alpha 4 beta 1) and VLA-5 ((alpha 5 beta 1) but was observed without changes in surface expression levels of these integrins. Studies using CrkL mutants demonstrated that the SH2 domain is partially required for enhancing cell adhesion, whereas the C-terminal SH3 domain as well as the tyrosine phosphorylation site (Y207) is dispensable. In contrast, the N-terminal SH3 domain, involved in binding C3G and other signaling molecules, was showed to play a crucial role, because a mutant defective of this domain showed an inhibitory effect on the cell adhesion to fibronectin, Furthermore, overexpression of C3G also increased the adhesion of hematopoietic cells to fibronectin, whereas a C3G mutant lacking the guanine nucleotide exchange domain abrogated the CrkL-induced increase in cell adhesion. On the other hand, a dominant negative mutant of H-Ras or that of Raf-1 enhanced the basal and CrkL-induced cell adhesion and that of R-Ras modestly decreased the adhesion. Taken together, these results indicate that the CrkL-C3G complex activates VLA-4 and VLA-5 in hematopoietic cells, possibly by activating the small GTP binding proteins, including R-Ras, through the guanine nucleotide exchange activity of C3G. (C) 1999 by The American Society of Hematology.