Furin inhibitor protects against neuronal cell death induced by activated NMDA receptors

Mariko Yamada,Bo Yuan,Nahoko Matsushima,Hideki Hayashi,Moe Yuuki,Norio Takagi

doi:10.1038/s41598-018-23567-0

Mariko Yamada, Bo Yuan + Show 4 more

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https://doi.org/10.1038/s41598-018-23567-0

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Abstract

The proprotein convertases (PCs) act as serine proteases and are known to convert diverse precursor proteins into their active forms. Among the PCs, furin has been considered to play a crucial role not only in embryogenesis, but also in the initiation and progression of certain pathologic conditions. However, the roles played by furin with respect to neuronal cell injuries remain to be determined. An excessive influx of Ca2+ through the N-methyl-d-aspartate (NMDA) receptor has been associated with diverse neurological and neurodegenerative disorders. The aim of this study was to achieve further insight into the pathophysiologic roles of furin in cultured cortical neurons. We demonstrated that furin inhibitors dose-dependently prevented neuronal injury induced by NMDA treatment. Neuronal injury induced by NMDA treatment was attenuated by the calpain inhibitor calpeptin. And the increase observed in the activity of calpain after NMDA treatment was significantly inhibited by these furin inhibitors. Furthermore, calpain-2 activity, which was evaluated by means of the immunoblotting assay, was increased by NMDA treatment. It was noteworthy that this increased activity was almost completely inhibited by a furin inhibitor. Our findings suggested that furin is involved in NMDA-induced neuronal injury by acting upstream of calpain.

Highlights

In the central nervous system, the ionotropic glutamate receptors, which are ligand-gated ion channels, play an important role in excitatory neurotransmission
We examined the effects of furin inhibitors on NMDA receptor-mediated neurotoxicity, which is associated with excessive Ca2+ influx into the neuron and has been implicated in a variety of neurodegenerative diseases
We examined the effects of furin inhibitor 1 (Fig. 3a) and furin inhibitor 2 (Fig. 3b) as well as those of several protease inhibitors, including inhibitors for γ-secretase (Fig. 3c), matrix metalloproteinase (MMP; Fig. 3d), and proprotein convertase subtilisin kexin 9 (PCSK9) (Fig. 3e) on NMDA-induced cortical cell injury

Summary

Introduction

In the central nervous system, the ionotropic glutamate receptors, which are ligand-gated ion channels, play an important role in excitatory neurotransmission. Among these receptors, the N-methyl-d-aspartate (NMDA) receptor is highly permeable to calcium and sodium ions[1]. The pathophysiological roles of furin in neuronal cell injuries induced by over-activated NMDA receptors remain to be determined. We examined the effects of furin inhibitors on NMDA receptor-mediated neurotoxicity, which is associated with excessive Ca2+ influx into the neuron and has been implicated in a variety of neurodegenerative diseases. Results were expressed as the percentage of these cells among the total number of Hoechst-positive cells and as the means ± SE in 4 independent experiments.

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