Effect of protein phosphorylation on neurite outgrowth in cultured embryonic Xenopus spinal neurons

Intracellular signaling pathways involved in neurite outgrowth have been extensively studied in a variety of cell systems. While most of these studies utilized continuous neuronal-like cell lines, fewer studies have been conducted in primary neuronal culture. One primary culture system that has recently been used to dissect the signaling pathways involved in axon guidance consists of spinal neurons derived from embryonic Xenopus laevis. In this study, we used Xenopus to study neurite outgrowth by treating neuronal cultures with pharmacological agents that activate or inhibit various protein kinases or that inhibit protein phosphatases. We found that agents which affected signaling via cAMP-dependent protein kinase, calmodulin, cyclin-dependent kinase 5, or protein phosphatases had effects on Xenopus neurite outgrowth that were similar to those reported in other primary neurons or in neuronal-like cell lines. However, agents which affected protein kinase C signaling had effects on Xenopus neurite outgrowth that were distinct from those reported in neuronal-like cell lines. Although continuous cell lines have several advantages for the dissection of signaling pathways involved in neurodevelopment, these observations underscore the importance of also using primary neurons to examine these pathways.