Sustained CREB Phosphorylation Is Associated with Neuritogenic Prostanoid Signaling in NSC-34 Cells

Neuritogenesis is essential for neuronal development and circuit formation. Although cAMP signaling downstream of Gs-coupled receptors is considered pro-neuritogenic, activation of these Gs-coupled receptors can produce divergent cellular outcomes. We previously showed that prostaglandin E₂ (PGE₂) induces neurite outgrowth in NSC-34 motor neuron-like cells predominantly through Gs-coupled E-prostanoid receptor 2 (EP2) signaling. The I-prostanoid receptor (IP) is also Gs-coupled, but whether its ligand PGI₂ elicits neuritogenesis remains unclear. Here, we compare the neuritogenic and signaling responses to PGE₂ and PGI₂ in NSC-34 cells. PGE₂ and the EP2 agonist butaprost increased the proportion of neurite-bearing cells, whereas PGI₂ and the IP agonist beraprost had no effect. PGI₂ and PGE₂ induced comparable cAMP accumulation and protein kinase A substrate phosphorylation, and elicited peak cAMP response element binding protein (CREB) phosphorylation at 1 h. However, only PGE₂ maintained significant CREB phosphorylation at 3-6 h. RNA sequencing at 4 h revealed broadly concordant transcriptional responses, while direct comparison identified Fst as the only gene expressed at higher levels under PGE₂ than under PGI₂. These findings suggest that the temporal profile of CREB phosphorylation, rather than the magnitude of early cAMP-PKA signaling, may be associated with differences in neuritogenic outcomes of Gs-coupled prostanoid signaling.