García-Bernal David, Wright Natalia, Sotillo-Mallo Elena, Nombela-Arrieta César, Stein Jens V, Bustelo Xosé R, Teixidó Joaquin
Department of Immunology, Centro de Investigaciones Biológicas, CSIC, 28006 Madrid, Spain.
Mol Biol Cell. 2005 Jul;16(7):3223-35. doi: 10.1091/mbc.e04-12-1049. Epub 2005 May 4.
The chemokine CXCL12 promotes T lymphocyte adhesion mediated by the integrin alpha4beta1. CXCL12 activates the GTPase Rac, as well as Vav1, a guanine-nucleotide exchange factor for Rac, concomitant with up-regulation of alpha4beta1-dependent adhesion. Inhibition of CXCL12-promoted Rac and Vav1 activation by transfection of dominant negative Rac or Vav1 forms, or by transfection of their siRNA, remarkably impaired the increase in T lymphocyte attachment to alpha4beta1 ligands in response to this chemokine. Importantly, inhibition of Vav1 expression by RNA interference resulted in a blockade of Rac activation in response to CXCL12. Adhesions in flow chambers and soluble binding assays using these transfectants indicated that initial ligand binding and adhesion strengthening mediated by alpha4beta1 were dependent on Vav1 and Rac activation by CXCL12. Finally, CXCL12-promoted T-cell transendothelial migration involving alpha4beta1-mediated adhesion was notably inhibited by expression of dominant negative Vav1 and Rac. These results indicate that activation of Vav1-Rac signaling pathway by CXCL12 represents an important inside-out event controlling efficient up-regulation of alpha4beta1-dependent T lymphocyte adhesion.
趋化因子CXCL12促进由整合素α4β1介导的T淋巴细胞黏附。CXCL12激活GTP酶Rac以及Rac的鸟嘌呤核苷酸交换因子Vav1，同时上调α4β1依赖性黏附。通过转染显性负性Rac或Vav1形式，或转染它们的小干扰RNA（siRNA）来抑制CXCL12促进的Rac和Vav1激活，显著削弱了T淋巴细胞对α4β1配体的黏附增加，这是对该趋化因子的反应。重要的是，通过RNA干扰抑制Vav1表达导致对CXCL12反应中Rac激活的阻断。使用这些转染细胞进行的流动腔室黏附及可溶性结合试验表明，由α4β1介导的初始配体结合和黏附增强依赖于CXCL12介导的Vav1和Rac激活。最后，CXCL12促进的涉及α4β1介导黏附的T细胞跨内皮迁移被显性负性Vav1和Rac的表达显著抑制。这些结果表明，CXCL12激活Vav1-Rac信号通路代表了一个重要的由内向外的事件，可控制α4β1依赖性T淋巴细胞黏附的有效上调。
