Department of Neuroscience, Program in Neurobiology and Behavior, Columbia University, New York, New York 10032, USA.
Dev Neurobiol. 2011 Oct;71(10):818-35. doi: 10.1002/dneu.20906.
Neurite outgrowth is a fundamental step in establishing proper neuronal connections in the developing central nervous system. Dynamic control of outgrowth has been attributed to changes in growth cone Ca2+ levels in response to extracellular cues. Here we have investigated a possible role for Ca2+ permeable kainate (KA) receptors in regulating neurite outgrowth of nociceptive-like dorsal root ganglion (DRG) neurons. To identify KA receptor subunits likely to be involved, we used quantitative RT-PCR on acutely dissociated DRG and dorsal horn neurons. DRG neurons expressed more GluK1, particularly the GluK1b spice variant, than dorsal horn neurons. Conversely, dorsal horn neurons expressed more GluK2, particularly GluK2a, than DRG neurons. Further, an RNA editing assay indicated that the majority of GluK1 and GluK2 mRNA transcripts in DRG were unedited. Imaging Ca2+ transients following application of a KA receptor agonist to DRG and dorsal horn co-cultures revealed increases in intracellular Ca2+ in the growth cones of DRG neurons. In the majority of cases, this increase in Ca2+ was partly or completely blocked by Joro spider toxin (JSTX), an antagonist for Ca2+-permeable AMPA and KA receptors. Treatment of DRG/dorsal horn co-cultures with KA for 18 hours suppressed neurite outgrowth while application of the rapidly desensitizing KA receptor agonist SYM 2081, the competitive AMPA/KA receptor antagonist, CNQX, and JSTX or philanthotoxin enhanced neurite outgrowth and prevented KA effects on neurite outgrowth. Thus, Ca2+ entry through KA receptors at the growth cone of DRG neurons may be an important regulator of neurite outgrowth.
神经突生长是中枢神经系统中建立正确神经元连接的基本步骤。生长锥 Ca2+ 水平的动态变化被认为是对外界刺激的反应，从而控制生长锥的生长。在这里，我们研究了钙通透性型的 kainate（KA）受体在调节伤害感受样背根神经节（DRG）神经元的神经突生长中的可能作用。为了鉴定可能参与的 KA 受体亚基，我们使用急性分离的 DRG 和背角神经元进行定量 RT-PCR。与背角神经元相比，DRG 神经元表达更多的 GluK1，特别是 GluK1b 变体。相反，背角神经元表达更多的 GluK2，特别是 GluK2a，而 DRG 神经元则较少。此外，RNA 编辑测定表明，DRG 中的大多数 GluK1 和 GluK2 mRNA 转录物未经编辑。在 DRG 和背角共培养物中应用 KA 受体激动剂后，观察到 Ca2+ 瞬变的成像，结果显示 DRG 神经元生长锥内的细胞内 Ca2+ 增加。在大多数情况下，这种 Ca2+ 的增加部分或完全被 Joro 蜘蛛毒素（JSTX）阻断，JSTX 是一种对 Ca2+ 通透性 AMPA 和 KA 受体的拮抗剂。用 KA 处理 DRG/背角共培养物 18 小时可抑制神经突生长，而应用快速脱敏的 KA 受体激动剂 SYM 2081、竞争性 AMPA/KA 受体拮抗剂 CNQX、JSTX 或 phanthotoxin 则增强神经突生长并防止 KA 对神经突生长的影响。因此，DRG 神经元生长锥中的 KA 受体的 Ca2+ 内流可能是神经突生长的重要调节剂。
