Nerve growth factor (NGF) stimulates numerous cellular physiological processes including growth, differentiation, survival, and maintains the phenotype of several neuronal types. Most of these NGF-induced processes require adaptation of the secretory pathway since they involve extensive remodeling of membranes and protein redistribution along newly formed neuritic processes. CREB3 transcription factors have emerged as signaling hubs for the regulation of numerous genes involved in secretory pathway and Golgi homeostasis, integrating stimuli from multiple sources to control secretion, post-translational modifications and trafficking of proteins. Although recent studies have focused on their role in the central nervous system, little is known about their participation in cell differentiation. Therefore, we aimed to analyze the expression and signaling mechanism of CREB3 transcription factor family members using the NGF-induced PC12 cell differentiation model. Results show that NGF treatment causes Golgi enlargement and a parallel increased expression of proteins and mRNAs encoding for proteins required for membrane transport (transport factors). Additionally, a significant increase in CREB3L2 protein and mRNA levels is detected in response to NGF. Both MAPK and cAMP signaling pathways are required for this response. Interestingly, CREB3L2 overexpression hampers NGF-induced neurite outgrowth while its inhibition enhances the morphological changes driven by NGF. In agreement, CREB3L2 overexpressing cells display higher immunofluorescence intensity of Rab5 GTPase (a negative regulator of PC12 differentiation) than control cells. Also, Rab5 immunofluorescence levels decrease in CREB3L2 depleted cells. Taken together, our findings imply that CREB3L2 is an important downstream effector of NGF-activated pathways leading to neuronal differentiation.

中文翻译：

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CREB3L2 调节神经生长因子诱导的细胞分化

神经生长因子 (NGF) 可刺激多种细胞生理过程，包括生长、分化、存活，并维持多种神经元类型的表型。大多数这些 NGF 诱导的过程需要分泌途径的适应，因为它们涉及膜的广泛重塑和沿着新形成的神经炎过程的蛋白质重新分布。CREB3 转录因子已成为调节参与分泌途径和高尔基体稳态的众多基因的信号中心，整合来自多个来源的刺激以控制分泌、翻译后修饰和蛋白质运输。尽管最近的研究集中在它们在中枢神经系统中的作用，但对它们参与细胞分化知之甚少。所以，我们旨在使用 NGF 诱导的 PC12 细胞分化模型分析 CREB3 转录因子家族成员的表达和信号传导机制。结果表明，NGF 处理导致高尔基体增大，并导致蛋白质和 mRNA 的表达增加，这些蛋白质和 mRNA 编码膜转运所需的蛋白质（转运因子）。此外，检测到响应 NGF 的 CREB3L2 蛋白和 mRNA 水平显着增加。这种反应需要 MAPK 和 cAMP 信号通路。有趣的是，CREB3L2 过表达阻碍了 NGF 诱导的神经突生长，而其抑制增强了 NGF 驱动的形态变化。一致地，CREB3L2 过表达细胞比对照细胞显示出更高的 Rab5 GTPase（PC12 分化的负调节因子）的免疫荧光强度。还有，Rab5 免疫荧光水平在 CREB3L2 耗尽的细胞中降低。总之，我们的发现意味着 CREB3L2 是导致神经元分化的 NGF 激活途径的重要下游效应器。