Fibronectin promotes calcium signaling by interferon-γ in human neutrophils via G-protein and sphingosine kinase-dependent mechanisms
Fibronectin promotes calcium signaling by interferon-γ in human neutrophils via G-protein and sphingosine kinase-dependent mechanisms
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DOI：
10.3109/15419060109080712
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发表时间：
2001-01-01
影响因子：
--
通讯作者：
Iversen, JG
中科院分区：
文献类型：
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作者：
Aas, V;Algeroy, S;Iversen, JG
在炎症中激活多形核白细胞(PMN)的一个常见的细胞内信号是胞浆钙浓度的变化。在此之前，我们已经证明了干扰素-γ在中性粒细胞中诱导瞬时钙信号，但仅在细胞内钙库耗尽之后。利用数字成像系统，我们发现PMN的粘附性对于干扰素-γ诱导的钙信号至关重要，并且由于PMN附着在最佳涂层上，即使在存在细胞外钙的情况下，钙信号也被激发，即非耗竭的钙库，粘附性纤维连接蛋白，纯的或通过明胶从血浆中提取的，与血清、血浆或玻璃体粘连蛋白涂层相比，改善了干扰素-γ的反应。与以往的观察结果一致，G蛋白抑制剂百日咳毒素可完全消除干扰素-γ诱导的纤维连接蛋白黏附细胞钙信号，神经鞘氨醇激酶抑制剂二甲基鞘氨醇(DMS)和N-乙酰鞘氨醇(N-Ac-Sp)也可抑制。PMN单独与纤维连接蛋白接触，在沉积到纤维连接蛋白涂层表面的细胞上测量，或通过将纤维连接蛋白添加到玻璃附着的细胞中来测量，引起瞬时钙信号。然而，悬液中的PMN对纤维连接蛋白或精氨酸-甘氨酸-天冬氨酸(RGD)的加入没有反应。百日咳毒素和鞘氨醇激酶抑制剂DMS、二氢鞘氨醇(DHS)和N-Ac-Sp也能明显抑制纤维连接蛋白诱导的钙信号。当鞘氨醇激酶活性的产物-1-磷酸鞘氨醇(S1-P)加入细胞中时，诱导出类似的钙信号，这依赖于百日咳毒素敏感的G蛋白的活性。最后，在干扰素-γ刺激前向细胞中加入S1-P，部分模拟了纤维连接蛋白的启动作用。综上所述，纤维连接蛋白接触本身可在中性粒细胞中激发钙信号，并通过干扰素-γ进一步促进钙信号的传递。我们认为，纤维连接蛋白可能激活鞘氨醇激酶，由此产生的鞘氨醇1-磷酸通过G蛋白依赖的机制诱导钙信号。显然，鞘氨醇激酶的活性也参与了干扰素-γ诱导的钙信号。
A common intracellular signal activating polymorphonuclear leukocytes (PMN) in inflammation is a change in cytosolic calcium concentration. Previously, we have shown that interferon-gamma (IFN-gamma) induces transient calcium signals in PMN, but only after intracellular calcium store depletion. Using a digital imaging system, we show that adhesion of PMN is critical for IFN-gamma-induced calcium signals, and with PMN attached to the optimal coating, the calcium signals are evoked even in presence of extracellular calcium, that is, non-depleted calcium stores, Adhesion to fibronectin, pure or extracted from plasma by gelatin, improved the IFN-gamma responses compared with serum, plasma, or vitronectin coats. In accordance with previous observations, IFN-gamma-induced calcium signals in fibronectin adherent cells were totally abolished by the G-protein inhibitor pertussis toxin and were also inhibited by the sphingosine kinase inhibitors dimethylsphingosine (DMS) and N-acetylsphingosine (N-Ac-Sp). PMN contact with fibronectin alone, measured in cells sedimenting onto a fibronectin-coated surface or by addition of fibronectin to glass-adherent cells, evoked transient calcium signals. However, PMN in suspension did not respond to the addition of fibronectin or arginine-glycine-aspartate (RGD). The fibronectin-induced calcium signals were also clearly depressed by pertussis toxin and by the sphingosine kinase inhibitors DMS, dihydrosphingosine (DHS), and N-Ac-Sp. When the product of sphingosine kinase activity, sphingosine 1-phosphate (S1-P), was added to the cells, similar calcium signals were induced, which were dependent on a pertussis toxin-sensitive G-protein activity. Finally, addition of S1-P to the cells prior to stimulation with IFN-gamma partly mimicked the priming effect of fibronectin. In conclusion, fibronectin contact evokes by itself a calcium signal in PMN and further promotes calcium signaling by IFN-gamma. We suggest that fibronectin might activate sphingosine kinase, and that the sphingosine 1-phosphate thereby generated induces a calcium signal via a G-protein-dependent mechanism. Apparently, sphingosine kinase activity is also involved in IFN-gamma induced calcium signals.