Myeloid immune checkpoint ILT3/LILRB4/gp49B can co-tether fibronectin with integrin on macrophages
Myeloid immune checkpoint ILT3/LILRB4/gp49B can co-tether fibronectin with integrin on macrophages
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DOI：
10.1093/intimm/dxac023
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发表时间：
2022-07-14
影响因子：
4.4
通讯作者：
Takai, Toshiyuki
中科院分区：
文献类型：
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作者：
Itoi, So;Takahashi, Naoyuki;Takai, Toshiyuki
LILRB4(B4，也称为ILT3/CD85k)是髓系细胞的免疫检查点，尽管其功能模式尚不清楚。我们最近发现了人B4及其小鼠同源基因gp49B的一个共同配体，即纤维连接蛋白(FN)N末端30 kDa结构域，这提出了一个问题，即B4/gp49B在识别血浆和/或细胞外基质中的FN时如何调节细胞活动。由于细胞外基质中的Fn被Fn结合的整合素所束缚，我们假设B4/gp49B会与细胞表面的整合素协同作用来拴住Fn，因此它们在空间上应该离整合素很近。这一情景提示了B4/gp49B的一种功能模式，通过这种模式来调节FN诱导的信号。在骨髓来源的巨噬细胞中发现FN下拉复合体含有gp49B和整合素β(1)。这三个分子在FN连接的巨噬细胞上的共聚焦荧光信号相互关联。当缺乏FN的巨噬细胞附着在培养板上时，gp49-整合素β(1)信号的相关性在焦点粘附处增加，支持gp49B和整合素β(1)在空间上变得更接近的观点。RAW264.7和THP-1细胞与固定化FN的黏附诱导脾酪氨酸激酶的磷酸化，在B4/gp49B缺乏的情况下其水平升高。因此，我们得出结论，B4/gp49B可以与同一细胞上顺式构型的整合素协同锚定FN，形成B4/gp49B-FN-整合素三联体，作为巨噬细胞局部黏附依赖的促炎信号的调节单元。
LILRB4 (B4, also known as ILT3/CD85k) is an immune checkpoint of myeloid lineage cells, albeit its mode of function remains obscure. Our recent identification of a common ligand for both human B4 and its murine ortholog gp49B as the fibronectin (FN) N-terminal 30 kDa domain poses the question of how B4/gp49B regulate cellular activity upon recognition of FN in the plasma and/or the extracellular matrix. Since FN in the extracellular matrix is tethered by FN-binding integrins, we hypothesized that B4/gp49B would tether FN in cooperation with integrins on the cell surface, thus they should be in close vicinity to integrins spatially. This scenario suggests a mode of function of B4/gp49B by which the FN-induced signal is regulated. The FN pull-down complex was found to contain gp49B and integrin beta (1) in bone marrow-derived macrophages. The confocal fluorescent signals of the three molecules on the intrinsically FN-tethering macrophages were correlated to each other. When FN-poor macrophages adhered to culture plates, the gp49-integrin beta (1) signal correlation increased at the focal adhesion, supporting the notion that gp49B and integrin beta (1) become spatially closer to each other there. Adherence of RAW264.7 and THP-1 cells to immobilized FN induced phosphorylation of spleen tyrosine kinase, whose level was augmented under B4/gp49B deficiency. Thus, we concluded that B4/gp49B can co-tether FN in cooperation with integrin in the cis configuration on the same cell, forming a B4/gp49B-FN-integrin triplet as a regulatory unit of a focal adhesion-dependent pro-inflammatory signal in macrophages.