Xu Tao, Zhang Lei, Geng Zhen H, Wang Hai-Bo, Wang Jin-Tao, Chen Ming, Geng Jian-Guo
Laboratory of Molecular Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, The Graduate School of Chinese Academy of Sciences, Shanghai, China.
Cell Adh Migr. 2007 Jul-Sep;1(3):115-23. doi: 10.4161/cam.1.3.4984. Epub 2007 Jul 5.
Endothelial and platelet P-selectin (CD62P) and leukocyte integrin alpha(M)beta(2) (CD11bCD18, Mac-1) are cell adhesion molecules essential for host defense and innate immunity. Upon inflammatory challenges, P-selectin binds to PSGL-1 (P-selectin glycoprotein ligand-1, CD162) to mediate neutrophil rolling, during which integrins become activated by extracellular stimuli for their firm adhesion in a G-protein coupled receptor (GPCR)-dependent mechanism. Here we show that cross-linking of PSGL-1 by dimeric or multimeric forms of platelet P-selectin, P-selectin receptor-globulin, anti-PSGL-1 mAb and its F(ab')2 induced adhesion of human neutrophils to fibrinogen (Fg) and intercellular cell adhesion molecule-1 (ICAM-1, CD54) and triggered a moderate clustering of alpha(M)beta(2), but monomeric forms of soluble P-selectin and anti-PSGL-1 Fab did not. Interestingly, P-selectin did not induce a detectable interleukine-8 (IL-8) secretion (<0.1 ng/ml) in 30 minutes, whereas a high concentration of IL-8 (>50 ng/ml) was required to increase neutrophil adhesion to Fg. P-selectin-induced neutrophil adhesion was significantly inhibited by PP2 (a Src kinase inhibitor), but not by pertussis toxin (PTX; a GPCR inhibitor). Activated platelets also increased neutrophil binding to fibrinogen and triggered tyrosine phosphorylation of cellular proteins. Our results indicate that P-selectin-induced integrin activation (Src kinase-dependent) is distinct from that elicited by cytokines, chemokines, chemoattractants (GPCR-dependent), suggesting that these two signal transduction pathways may cooperate for maximal activation of leukocyte integrins.
内皮细胞和血小板的P-选择素（CD62P）以及白细胞整合素α(M)β(2)（CD11bCD18，Mac-1）是宿主防御和固有免疫所必需的细胞黏附分子。在炎症刺激下，P-选择素与PSGL-1（P-选择素糖蛋白配体-1，CD162）结合以介导中性粒细胞滚动，在此过程中整合素通过细胞外刺激以G蛋白偶联受体（GPCR）依赖性机制被激活，从而实现牢固黏附。在此我们表明，血小板P-选择素的二聚体或多聚体形式、P-选择素受体球蛋白、抗PSGL-1单克隆抗体及其F(ab')2对PSGL-1进行交联，可诱导人中性粒细胞与纤维蛋白原（Fg）和细胞间细胞黏附分子-1（ICAM-1，CD54）黏附，并引发α(M)β(2)适度聚集，但可溶性P-选择素的单体形式和抗PSGL-1 Fab则不会。有趣的是，P-选择素在30分钟内未诱导出可检测到的白细胞介素-8（IL-8）分泌（<0.1 ng/ml），而需要高浓度的IL-8（>50 ng/ml）才能增加中性粒细胞与Fg的黏附。PP2（一种Src激酶抑制剂）可显著抑制P-选择素诱导的中性粒细胞黏附，但百日咳毒素（PTX；一种GPCR抑制剂）则无此作用。活化的血小板也会增加中性粒细胞与纤维蛋白原的结合，并引发细胞蛋白的酪氨酸磷酸化。我们的结果表明，P-选择素诱导的整合素激活（Src激酶依赖性）与细胞因子、趋化因子、趋化剂诱导的激活（GPCR依赖性）不同，这表明这两条信号转导途径可能协同作用以使白细胞整合素实现最大程度的激活。
