The role of the CPNKEKEC sequence in the β2 subunit I domain in regulation of integrin αLβ2 (LFA-1)
The role of the CPNKEKEC sequence in the β2 subunit I domain in regulation of integrin αLβ2 (LFA-1)
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DOI：
10.4049/jimmunol.168.5.2296
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发表时间：
2002-03-01
影响因子：
4.4
通讯作者：
Takada, Y
中科院分区：
文献类型：
--
作者：
Kamata, T;Tieu, KK;Takada, Y
整合素α（L）β（2）的α（L）I（插入的或相互作用的）结构域在活化后经历构象变化。最近的研究表明，分离的、活化的aL I结构域足以与强配体结合，表明β 2亚基仅间接参与。目前还不清楚α，I结构域的活性是否受β 2亚基的调节。在这项研究中，我们证明了将α（L）I结构域中的二硫键连接的CPNKEKEC序列（残基169-176）与相应的β（3）序列交换，或将Lys（174）突变为Thr，组成性激活α（L）β（2）与ICAM-1的结合。这些突变体不需要Mn ~（2+）与ICAM-1结合，并且对Ca ~（2+）的抑制作用不敏感。我们还在CPNKEKEC序列中定位了mAb 24表位的一个组分（β（2）整联蛋白激活的报告基因）。β（2）I结构域的Glu（173）和Glu（175）被鉴定为对mAb 24结合至关重要。因为表位在β 2整联蛋白活化后高度表达，所以很可能CPNKEKEC序列在活化后暴露或经历构象变化。α（L）I结构域的缺失没有消除蟹24表位。这证实了α（L）I结构域对于mAb 24结合不是关键的，并表明mAb 24检测到部分表达于β（2）亚基I结构域的变化。这些结果表明，β（2）I结构域的CPNKEKEC序列参与调节α（L）I结构域。
The alpha(L) I (inserted or interactive) domain of integrin alpha(L)beta(2) undergoes conformational changes upon activation. Recent studies show that the isolated, activated aL I domain is sufficient for strong ligand binding, suggesting the (32 subunit to be only indirectly involved. It has been unclear whether the activity, of the a, I domain is regulated by the (32 subunit. In this study, we demonstrate that swapping the disulfide-Linked CPNKEKEC sequence (residues 169-176) in the alpha(L) I domain with a corresponding beta(3) sequence, or mutating Lys(174) to Thr, constitutively activates alpha(L)beta(2) binding to ICAM-1. These mutants do not require Mn2+ for ICAM-1 binding and are insensitive to the inhibitory effect of Ca2+. We have also localized a component of the mAb 24 epitope (a reporter of beta(2) integrin activation) in the CPNKEKEC sequence. Glu(173) and Glu(175) of the beta(2) I domain are identified as critical for mAb 24 binding. Because the epitope is highly expressed upon beta(2) integrin activation, it is likely that the CPNKEKEC sequence is exposed or undergoes conformational changes upon activation. Deletion of the alpha(L) I domain did not eliminate the crab 24 epitope. This confirms that the alpha(L) I domain is not critical for mAb 24 binding, and indicates that mAb 24 detects a change expressed in part in the beta(2) subunit I domain. These results suggest that the CPNKEKEC sequence of the beta(2) I domain is involved in regulating the alpha(L) I domain.