Application of Antibodies to Neuronally Expressed Nogo-A Increases Neuronal Survival and Neurite Outgrowth.

Mukti Patel,Vini Nagaraj,Anmol Singh Johal,Arihant Seth,Nikki Kurian,Jada Gore,Neha Arsha,Melitta Schachner,Thomas Theis,Helen Baixia Hao

doi:10.3390/ijms21155417

Abstract

Nogo-A, a glycoprotein expressed in oligodendrocytes and central nervous system myelin, inhibits regeneration after injury. Antibodies against Nogo-A neutralize this inhibitory activity, improve locomotor recovery in spinal cord-injured adult mammals, and promote regrowth/sprouting/saving of damaged axons beyond the lesion site. Nogo-A is also expressed by neurons. Complete ablation of Nogo-A in all cell types expressing it has been found to lead to recovery in some studies but not in others. Neuronal ablation of Nogo-A reduces axonal regrowth after injury. In view of these findings, we hypothesized that, in addition to neutralizing Nogo-A in oligodendrocytes and myelin, Nogo-A antibodies may act directly on neuronal Nogo-A to trigger neurite outgrowth and neuronal survival. Here, we show that polyclonal and monoclonal antibodies against Nogo-A enhance neurite growth and survival of cultured cerebellar granule neurons and increase expression of the neurite outgrowth-promoting L1 cell adhesion molecule and polysialic acid. Application of inhibitors of signal transducing molecules, such as c-src, c-fyn, protein kinase A, and casein kinase II reduce antibody-triggered neurite outgrowth. These observations indicate that the recovery-promoting functions of antibodies against Nogo-A may not only be due to neutralizing Nogo-A in oligodendrocytes and myelin, but also to their interactions with Nogo-A on neurons.

Highlights

Myelin-associated inhibitory molecules expressed in the adult central nervous system of mammals prevent axonal regrowth/sprouting and reconstruction of networks
Nogo-A, the largest isoform in the Nogo gene family, which includes Nogo-B and Nogo-C, is a guidance molecule that was initially described as a potent inhibitor of neuritogenesis and regeneration after central nervous system injury in adult mammals [2,3]
With the aim to investigate whether antibodies against Nogo-A would neutralize glial Nogo-A, and affect neurite outgrowth and neuronal survival in vitro, we found that monoclonal and polyclonal antibodies against Nogo-A enhance neurite outgrowth as assayed in vitro with the paradigmatic mouse cerebellar granule neurons

Summary

Introduction

Myelin-associated inhibitory molecules expressed in the adult central nervous system of mammals prevent axonal regrowth/sprouting and reconstruction of networks. Inhibitory molecules reduce restoration of disturbed networks after injury [1]. Among these inhibitory molecules, Nogo-A was the first to be identified as an important player. Other studies [10] did not report these growth cone-repelling effects with similar transgenic animals with or without Nogo-A expression. The reason for this discrepancy is not clear

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Conclusion