The Sema3A receptor Plexin-A1 suppresses supernumerary axons through Rap1 GTPases

Nannan Wang,Andreas W. Püschel,Pratibha Dhumale,Joanna Chiang

doi:10.1038/s41598-018-34092-5

Nannan Wang, Andreas W. Püschel + Show 2 more

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https://doi.org/10.1038/s41598-018-34092-5

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Abstract

The highly conserved Rap1 GTPases perform essential functions during neuronal development. They are required for the polarity of neuronal progenitors and neurons as well as for neuronal migration in the embryonic brain. Neuronal polarization and axon formation depend on the precise temporal and spatial regulation of Rap1 activity by guanine nucleotide exchange factors (GEFs) and GTPases-activating proteins (GAPs). Several Rap1 GEFs have been identified that direct the formation of axons during cortical and hippocampal development in vivo and in cultured neurons. However little is known about the GAPs that limit the activity of Rap1 GTPases during neuronal development. Here we investigate the function of Sema3A and Plexin-A1 as a regulator of Rap1 GTPases during the polarization of hippocampal neurons. Sema3A was shown to suppress axon formation when neurons are cultured on a patterned substrate. Plexin-A1 functions as the signal-transducing subunit of receptors for Sema3A and displays GAP activity for Rap1 GTPases. We show that Sema3A and Plexin-A1 suppress the formation of supernumerary axons in cultured neurons, which depends on Rap1 GTPases.

Highlights

Small GTPases of the Ras superfamily perform essential functions throughout neuronal development and in mature neurons[1]
Our results suggest that Sema3A acts as an autocrine signal through Plexin-A1, which restricts the activity of Rap[1] and thereby prevents the formation of supernumerary axons
Suppressing Plexin-A1 function by a dominant-negative construct or a knockdown had a similar effect while expression of constitutively active Plexin-A1 blocked axon formation

Summary

Introduction

Small GTPases of the Ras superfamily perform essential functions throughout neuronal development and in mature neurons[1]. The phenotype of plexin mutants confirmed that GAP activity is essential for their function in vivo and provided evidence for a regulation of Ras and Rap[1] GTPases[22,23,35]. Sema3A directs the orientation of axons and apical dendrites in the developing cortex[44,45,46,47] It can regulate the establishment of neuronal polarity by promoting the formation of dendrites and suppressing the extension of axons when neurons are cultured on a patterned substrate with stripes of immobilized Sema3A48,49. In cultures of sensory neurons from embryonic dorsal root ganglia, Sema3A accelerates the establishment of neuron polarity[50] It remains to be investigated if plexins regulate the activity of Rap[1] GTPases during neuronal polarization

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