Goda S, Imai T, Yoshie O, Yoneda O, Inoue H, Nagano Y, Okazaki T, Imai H, Bloom E T, Domae N, Umehara H
Departments ofInternal Medicine and Periodontology, Osaka Dental University, Hanazono-cho, Hirakata-shi, Osaka, Japan.
J Immunol. 2000 Apr 15;164(8):4313-20. doi: 10.4049/jimmunol.164.8.4313.
Leukocyte adhesion and trafficking at the endothelium requires both cellular adhesion molecules and chemotactic factors. A newly identified CX3C chemokine, fractalkine, expressed on activated endothelial cells, plays an important role in leukocyte adhesion and migration. We examined the functional effects of fractalkine on beta1 and beta2 integrin-mediated adhesion using a macrophage-like cell line, THP-1 cells. In this study, we report that THP-1 cells express mRNA encoding a receptor for fractalkine, CX3CR1, determined by Northern blotting. Scatchard analysis using fractalkine-SEAP (secreted form of placental alkaline phosphatase) chimeric proteins revealed that THP-1 cells express a single class of CX3CR1 with a dissociation constant of 30 pM and a mean expression of 440 sites per cell. THP-1 cells efficiently adhered, in a fractalkine-dependent manner, to full-length of fractalkine immobilized onto plastic and to the membrane-bound form of fractalkine expressed on ECV304 cells or TNF-alpha-activated HUVECs. Moreover, soluble-fractalkine enhanced adhesion of THP-1 cells to fibronectin and ICAM-1 in a dose-dependent manner. Pertussis toxin, an inhibitor of Gi, inhibited the fractalkine-mediated enhancement of THP-1 cell adhesion to fibronectin and ICAM-1. Finally, we found that soluble-fractalkine also enhanced adhesion of freshly separated monocytes to fibronectin and ICAM-1. These results indicate that fractalkine may induce firm adhesion between monocytes and endothelial cells not only through an intrinsic adhesion function itself, but also through activation of integrin avidity for their ligands.
白细胞在内皮细胞处的黏附和迁移需要细胞黏附分子和趋化因子。一种新发现的CX3C趋化因子，即活化内皮细胞上表达的fractalkine，在白细胞黏附和迁移中起重要作用。我们使用巨噬细胞样细胞系THP-1细胞研究了fractalkine对β1和β2整合素介导的黏附的功能影响。在本研究中，我们报告通过Northern印迹法确定THP-1细胞表达编码fractalkine受体CX3CR1的mRNA。使用fractalkine-SEAP（胎盘碱性磷酸酶分泌形式）嵌合蛋白进行的Scatchard分析表明，THP-1细胞表达一类CX3CR1，解离常数为30 pM，平均每个细胞表达440个位点。THP-1细胞以fractalkine依赖的方式有效地黏附于固定在塑料上的全长fractalkine以及ECV304细胞或TNF-α激活的人脐静脉内皮细胞（HUVECs）上表达的膜结合形式的fractalkine。此外，可溶性fractalkine以剂量依赖的方式增强THP-1细胞与纤连蛋白和细胞间黏附分子-1（ICAM-1）的黏附。百日咳毒素（一种Gi抑制剂）抑制fractalkine介导的THP-1细胞与纤连蛋白和ICAM-1黏附的增强。最后，我们发现可溶性fractalkine也增强了新鲜分离的单核细胞与纤连蛋白和ICAM-1的黏附。这些结果表明，fractalkine不仅可以通过其自身固有的黏附功能，还可以通过激活整合素对其配体的亲和力来诱导单核细胞与内皮细胞之间的牢固黏附。
