Activation of the Ras signaling pathway by the CD40 receptor.
Activation of the Ras signaling pathway by the CD40 receptor.
复制标题
CD40 受体激活 Ras 信号通路。
作者：
E. Gulbins;B. Brenner;K. Schlottmann;U. Koppenhoefer;O. Linderkamp;K. Coggeshall;F. Lang
CD40受体是调节B淋巴细胞增殖、成熟、抗体类转换和细胞存活的重要分子。在本研究中，我们确定了由CD40受体交联物触发的信号转导事件。抗CD40抗体刺激Daudi B细胞可激活p21ras，p21ras是调节细胞生长和分化的重要转换点。RAS的激活与rac1和MEK-1的刺激以及磷脂酰肌醇3-激酶的酪氨酸磷酸化有关。通过转导跨显性抑制RAS来抑制内源性RAS，可以阻止CD40受体触发的酪氨酸磷酸化或磷脂酰肌醇3-激酶、rac1或MEK-1的刺激，证明CD40激活了RAS通路。在CD40刺激后，蛋白酪氨酸激酶和二甘油三酯在RAS激活中具有协同作用。为了支持二甘油酯的作用，我们检测到细胞磷脂酰胆碱含量下降了30+/-5%，这与CD40诱导的二酰甘油合成增加了三倍相关。为了支持蛋白酪氨酸激酶的作用，我们测量了p56lyn和p58blk激酶活性的五到八倍的刺激。这些结果提示，RAS途径通过src激酶和磷脂酶的相加作用而被激活，这可能在CD40受体结合后的生物效应的调节中起重要作用。
The CD40 receptor is an important molecule regulating B lymphocyte proliferation, maturation, Ab class switching, and cell survival. In the present study, we identified signal transduction events triggered by cross-linking the CD40 receptor. Stimulation of Daudi B cells with anti-CD40 resulted in activation of p21ras, an important switch point in the regulation of cell growth and differentiation. Ras activation correlated with a stimulation of Rac1 and MEK-1 as well as tyrosine phosphorylation of phosphatidylinositol 3-kinase. Inhibition of endogenous Ras by transfection of transdominant inhibitory Ras prevented tyrosine phosphorylation or stimulation of phosphatidylinositol 3-kinase, Rac1, or MEK-1 upon CD40 receptor triggering, proving an activation of the Ras pathway by CD40. Ras activation was partially inhibited by either herbimycin A or calphostin pretreatment and completely inhibited by preincubation with a combination of both inhibitors, indicating a synergistic role for protein tyrosine kinases and diglycerides in Ras activation after CD40 stimulation. In support of a role for diglycerides, we detected a 30 +/- 5% decrease of cellular phosphatidylcholine content, correlating with a threefold increase of diacylglycerol synthesis induced by CD40. Supporting a role for protein tyrosine kinase, we measured a five- to eightfold stimulation of p56lyn and p58blk kinase activity. These results suggest the activation of the Ras pathway via an additive function of src kinases and phospholipases that may be important in the mediation of biologic effects after CD40 receptor engagement.