Genetic perturbation of the putative cytoplasmic membrane-proximal salt bridge aberrantly activates α4 integrins
Genetic perturbation of the putative cytoplasmic membrane-proximal salt bridge aberrantly activates α4 integrins
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DOI：
10.1182/blood-2008-03-144543
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发表时间：
2008-12-15
期刊：
影响因子：
20.3
通讯作者：
Shimaoka, Motomu
中科院分区：
文献类型：
--
作者：
Imai, Yoichi;Park, Eun Jeong;Shimaoka, Motomu
α（4）整联蛋白在白细胞迁移和组织特异性归巢中起关键作用。整合素结合配体的能力是由胞质结构域中触发的活化依赖性构象变化动态调节的。NMR溶液结构定义了α（平行于B）β（3）整联蛋白胞质尾之间的假定的近膜盐桥，其将整联蛋白抑制在其低亲和力状态。然而，这种盐桥在α（4）整联蛋白调节中的生理重要性仍有待阐明。为了解决这个问题，我们通过突变α 4整合素中保守的细胞质精氨酸R-GFFKR来破坏鼠生殖系中的盐桥。在来自敲入小鼠（α（4）-R/A（GFFKR））的淋巴细胞中，α 4 β 1和α 4 β 7整联蛋白表现出组成性上调的配体结合。然而，这些细胞穿过VCAM-1和MAdCAM-1基质或穿过内皮单层的迁移减少。尾部的扰动脱离似乎导致α 4-R/A（GFFKR）淋巴细胞的细胞迁移减少。在体内，α 4-R/A（GFFKR）细胞表现出增加的Peyer集合静脉的牢固粘附，但减少归巢到肠道。我们的研究结果表明，膜近端盐桥在支持适当的α（4）整合素粘附动力学中起着关键作用。这种相互作用的丧失使非粘附构象不稳定，从而扰乱了有效细胞迁移所需的粘附和去粘附的适当平衡循环。（血。2008; 112：5007-5015）
alpha(4) integrins play a pivotal role in leukocyte migration and tissue-specific homing. The ability of integrins to bind ligand is dynamically regulated by activation-dependent conformational changes triggered in the cytoplasmic domain. An NMR solution structure defined a putative membrane-proximal salt bridge between the alpha(parallel to b)beta(3) integrin cytoplasmic tails, which restrains integrins in their low-affinity state. However, the physiological importance of this salt bridge in alpha(4) integrin regulation remains to be elucidated. To address this question, we disrupted the salt bridge in murine germ line by mutating the conserved cytoplasmic arginine R-GFFKR in alpha(4) integrins. In lymphocytes from knock-in mice (alpha(4)-R/A(GFFKR)), alpha 4 beta 1 and alpha 4 beta 7 integrins exhibited constitutively up-regulated ligand binding. However, transmigration of these cells across VCAM-1 and MAdCAM-1 substrates, or across endothelial monolayers, was reduced. Perturbed detachment of the tail appeared to cause the reduced cell migration of alpha 4-R/A(GFFKR) lymphocytes. In vivo, alpha 4-R/A(GFFKR) cells exhibited increased firm adhesion to Peyer patch venules but reduced homing to the gut. Our results demonstrate that the membrane-proximal salt bridge plays a critical role in supporting proper alpha(4) integrin adhesive dynamics. Loss of this interaction destabilizes the nonadhesive conformation, and thereby perturbs the properly balanced cycles of adhesion and deadhesion required for efficient cell migration.(Blood. 2008; 112: 5007-5015)