Lipopolysaccharide-induced change of phosphorylation of two cytosolic proteins in human monocytes is prevented by inhibitors of ADP-ribosylation.
Lipopolysaccharide-induced change of phosphorylation of two cytosolic proteins in human monocytes is prevented by inhibitors of ADP-ribosylation.
复制标题
ADP-核糖基化抑制剂可防止脂多糖诱导的人单核细胞中两种胞浆蛋白的磷酸化变化。
作者：
H. Heine;A. Ulmer;H. Flad;S. Hauschildt
内毒素与人单核细胞的相互作用引起36 kDa和38 kDa胞浆蛋白磷酸标记的改变(p36/38)。这一特性是由体外研究确定的，其他单核细胞激活剂也具有这种特性。磷酸化的p36/38不同于单核细胞中表达的p38、42-kDa和44-kDa的丝裂原激活蛋白激酶亚型。内毒素拮抗剂是大肠杆菌类脂A的合成四酰化双磷酸盐前体(也称为化合物406，脂类Iva或前体Ia)，它占据了内毒素的结合位点，防止了内毒素诱导的两种蛋白质磷酸标记的变化。抗CD14抗体可抑制低浓度(10 ng/ml)的LPS诱导的蛋白质磷酸化，而高浓度(1微克/ml)的抗CD14抗体不能阻止蛋白质的磷酸化。除了磷酸化，蛋白质的ADP-核糖化还参与了许多生物过程。在这里，我们展示了ADP-核糖化的抑制剂，即间碘苯甲基胍和烟酰胺，抑制了脂多糖启动的p36/38的改变的磷酸化。这种p36/38磷酸标记的缺失伴随着肿瘤坏死因子-α和白介素6的mRNA和蛋白产生的抑制。IL-1的合成不受影响。这表明，这些抑制剂干扰了IL-6和TNF-α产生的特定步骤，而这两个步骤并不是合成IL-1所必需的。综上所述，这些数据表明，ADP-核糖化可能参与了内毒素诱导的两种胞浆蛋白(p36/38)的磷酸化状态的改变，并且这些蛋白调节了导致TNF-α和IL-6释放的细胞过程。
Interaction of LPS with human monocytes causes altered phosphate labeling of cytosolic proteins of 36 kDa and 38 kDa (p36/38). This property, determined by in vitro studies, is shared by other monocyte activators. Phosphorylated p36/38 are distinct from p38, 42-kDa, and 44-kDa isoforms of mitogen-activated protein kinases expressed in monocytes. Occupation of LPS binding sites by a LPS antagonist, the synthetic tetraacylated bisphosphate precursor of Escherichia coli lipid A (also known as compound 406, lipid IVa, or precursor Ia), prevents LPS-induced changes in the phosphate labeling of the two proteins. Abs against CD14 inhibit protein phosphorylation induced by low concentrations of LPS (10 ng/ml), whereas at high concentrations (1 microgram/ml), the Abs fail to prevent phosphorylation. In addition to phosphorylation, ADP-ribosylation of proteins has been implicated in a number of biologic processes. Here we show that inhibitors of ADP-ribosylation, namely meta-iodobenzylguanidine and nicotinamide, inhibit LPS-initiated altered phosphorylation of p36/38. This loss of phosphate labeling of p36/38 is accompanied by an inhibition of TNF-alpha and Il-6 mRNA and protein production. The synthesis of IL-1 is not affected. This suggests that the inhibitors interfere with specific steps in IL-6 and TNF-alpha production, which are not required for IL-1 synthesis. Taken together, the data indicate that ADP-ribosylation may be involved in LPS-induced alteration of the phosphorylation state of two cytosolic proteins (p36/38) and that these proteins modulate cellular processes leading to TNF-alpha and IL-6 release.