Na+/H+ exchanger NHE1, a major determinant of intracellular pH (pHi) in mammalian central neurons, promotes neurite outgrowth under both basal and netrin-1-stimulated conditions. The small GTP binding proteins and their effectors have a dominant role in netrin-1-stimulated neurite outgrowth. Since NHE1 has been shown previously to work downstream of the Rho GTPases-mediated polarized membrane protrusion in non-neuronal cells, we examined whether NHE1 has a similar relationship with Cdc42, Rac1 and RhoA in neuronal morphogenesis. Interestingly, our results suggest the possibility that NHE1 acting upstream of Rho GTPases to promote neurite outgrowth induced by netrin-1. First, we found that netrin-1-induced increases in the activities of Rho GTPases using FRET (Forster Resonance Energy Transfer) analyses in individual growth cones; furthermore, their increased activities were abolished by cariporide, a specific NHE1 inhibitor. Second, NHE1 inhibition had no effect on neurite retraction induced by L-α-Lysophosphatidic acid (LPA), a potent RhoA activator. The regulation of Rho GTPases by NHE1 was further evidenced by reduced Rac1, Cdc42 and RhoA activities in NHE1-null neurons. Taken together, our findings suggest that NHE1-dependent neuronal morphogenesis involves the activation of Rho-family of small GTPases.

中文翻译：

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Na / H交换剂NHE1在rhGTP酶的上游起作用，促进神经突向外生长。

Na + / H +交换子NHE1是哺乳动物中枢神经元中细胞内pH（pHi）的主要决定因素，在基础和netrin-1刺激的条件下均可促进神经突生长。小的GTP结合蛋白及其效应物在netrin-1刺激的神经突增生中起主要作用。由于以前已经显示NHE1在非神经元细胞中Rho GTPases介导的极化膜突起的下游起作用，因此我们检查了NHE1在神经元形态发生中是否与Cdc42，Rac1和RhoA具有相似的关系。有趣的是，我们的结果表明NHE1在Rho GTPases上游起作用，有可能促进netrin-1诱导的神经突生长。首先，我们发现在单个生长锥中使用FRET（Forster共振能量转移）分析，netrin-1诱导Rho GTPases活性增加；此外，它们的活性增加被特定的NHE1抑制剂cariporide取消。其次，NHE1抑制对有效的RhoA激活剂L-α-Lysophosphatidicacid（LPA）诱导的神经突回退没有影响。NHE1对Rho GTPases的调节作用还可以通过NHE1无神经元中Rac1，Cdc42和RhoA活性降低来进一步证明。两者合计，我们的发现表明，NHE1依赖的神经元形态发生涉及小GTPases Rho家族的激活。