Chemical & Pharmaceutical Engineering, Singapore-MIT Alliance, 4 Engineering Drive 3, Singapore, Singapore.
BMC Neurosci. 2013 Dec 12;14:153. doi: 10.1186/1471-2202-14-153.
Synergistic multi-ligand treatments that can induce neuronal differentiation offer valuable strategies to regulate and modulate neurite outgrowth. Whereas the signaling pathways mediating single ligand-induced neurite outgrowth, such as Akt, extracellular signal-regulated kinase (Erk), c-Jun N-terminal kinase (JNK), and p38 mitogen-activated protein kinase (P38), have been extensively studied, the mechanisms underlying multi-ligand synergistic neurite outgrowth are poorly understood. In an attempt to gain insight into synergistic neurite outgrowth, PC12 cells were treated with one of three combinations: pituitary adenylate cyclase-activating peptide (PACAP) with epidermal growth factor (EP), basic fibroblast growth factor (FP), or nerve growth factor (NP) and then challenged with the appropriate kinase inhibitors to assess the signaling pathways involved in the process.
Response surface analyses indicated that synergistic neurite outgrowth was regulated by distinct pathways in these systems. Synergistic increases in the phosphorylation of Erk and JNK, but not Akt or P38, were observed with the three growth factor-PACAP combinations. Unexpectedly, we identified a synergistic increase in JNK phosphorylation, which was involved in neurite outgrowth in the NP and FP, but not EP, systems. Inhibition of JNK using the SP600125 inhibitor reduced phosphorylation of 90 kDa ribosomal S6 kinase (P90RSK) in the NP and FP, but not EP, systems. This suggested the involvement of P90RSK in mediating the differential effects of JNK in synergistic neurite outgrowth.
Taken together, these findings reveal the involvement of distinct signaling pathways in regulating neurite outgrowth in response to different synergistic growth factor-PACAP treatments. Our findings demonstrate a hitherto unrecognized mechanism of JNK-P90RSK in mediating synergistic neurite outgrowth induced by the co-treatment of growth factors and PACAP.
能够诱导神经元分化的协同多配体治疗为调节和调制神经突生长提供了有价值的策略。虽然介导单一配体诱导的神经突生长的信号通路，如 Akt、细胞外信号调节激酶 (Erk)、c-Jun N 端激酶 (JNK) 和 p38 丝裂原激活蛋白激酶 (P38)，已经被广泛研究，但多配体协同神经突生长的机制尚不清楚。为了深入了解协同神经突生长，用三种组合之一处理 PC12 细胞：垂体腺苷酸环化酶激活肽 (PACAP) 与表皮生长因子 (EP)、碱性成纤维细胞生长因子 (FP) 或神经生长因子 (NP)，然后用适当的激酶抑制剂处理，以评估参与该过程的信号通路。
响应面分析表明，这些系统中的协同神经突生长受不同途径的调节。在这三种生长因子-PACAP 组合中，观察到 Erk 和 JNK 磷酸化的协同增加，但 Akt 或 P38 没有增加。出乎意料的是，我们发现 JNK 磷酸化的协同增加与 NP 和 FP 系统中的神经突生长有关，但与 EP 系统无关。使用 SP600125 抑制剂抑制 JNK 减少了 NP 和 FP 系统中 90kDa 核糖体 S6 激酶 (P90RSK) 的磷酸化，但在 EP 系统中没有减少。这表明 P90RSK 参与介导 JNK 在协同神经突生长中的差异效应。
综上所述，这些发现揭示了不同信号通路在调节不同协同生长因子-PACAP 处理后神经突生长中的作用。我们的研究结果表明，JNK-P90RSK 在介导生长因子和 PACAP 共同处理诱导的协同神经突生长中存在一种以前未被认识的机制。
