CD40-activated CD40L reverse signaling is a major physiological regulator of axon and dendrite growth from developing hippocampal pyramidal neurons. Here we have studied how CD40L-mediated reverse signaling promotes the growth of these processes. Cultures of hippocampal pyramidal neurons were established from Cd40^−/− mouse embryos to eliminate endogenous CD40/CD40L signaling, and CD40L reverse signaling was stimulated by a CD40-Fc chimera. CD40L reverse signaling increased phosphorylation and hence activation of proteins in the PKC, ERK, and JNK signaling pathways. Pharmacological activators and inhibitors of these pathways revealed that whereas activation of JNK inhibited growth, activation of PKC and ERK1/ERK2 enhanced growth. Experiments using combinations of pharmacological reagents revealed that these signaling pathways regulate growth by functioning as an interconnected and interdependent network rather than acting in a simple linear sequence. Immunoprecipitation studies suggested that stimulation of CD40L reverse signaling generated a receptor complex comprising CD40L, PKCβ, and the Syk tyrosine kinase. Our studies have begun to elucidate the molecular network and interactions that promote axon and dendrite growth from developing hippocampal neurons following activation of CD40L reverse signaling.

CD40激活的CD40L反向信号传导是海马锥体神经元发育过程中轴突和树突生长的主要生理调节剂。在这里，我们研究了CD40L介导的反向信号传导如何促进这些过程的生长。从Cd40 ^-/-建立海马锥体神经元的培养物小鼠胚胎消除内源性CD40 / CD40L信号传导，而CD40-Fc嵌合体刺激CD40L反向信号传导。CD40L反向信号传导增加了磷酸化，从而激活了PKC，ERK和JNK信号传导通路中的蛋白质。这些途径的药理激活剂和抑制剂表明，尽管JNK的激活抑制了生长，但PKC和ERK1 / ERK2的激活却促进了生长。使用药理学试剂的组合进行的实验表明，这些信号传导途径通过充当相互连接和相互依赖的网络而不是按简单的线性顺序起作用来调节生长。免疫沉淀研究表明，对CD40L反向信号的刺激产生了一个包含CD40L，PKCβ和Syk酪氨酸激酶的受体复合物。