Furin-mediated cleavage of LRP1 and increase in ICD of LRP1 after cerebral ischemia and after exposure of cultured neurons to NMDA

Mariko Yamada,Daisuke Inoue,Yui Iwatani,Meiko Ohata,Shoko Sato,Kaori Suzuki,Norio Takagi,Hideki Hayashi,Bo Yuan

doi:10.1038/s41598-019-48279-x

Abstract

The N-methyl-D-aspartate (NMDA) receptor has been implicated in several neurodegenerative diseases, including stroke. Low-density lipoprotein receptor-related protein 1 (LRP1) plays pivotal roles in endocytosis and signaling in the cell. Immature LRP1 is processed by furin in the trans-Golgi network (TGN) and transported to the cell surface as its mature form. Activation of mature LRP1 exerts a protective effect against glutamate-induced degeneration of the rat retinal ganglion cells, as was shown in our previous study. However, the roles of LRP1 in the pathogenesis of excitotoxic neuronal injuries remain to be determined. The aim of this present study was to achieve further insight into the pathophysiologic roles of LRP1 after excitotoxic neuronal injuries. Our findings are the first to demonstrate that LRP1 was significantly cleaved by furin after cerebral ischemia in rats as well as after exposure of cultured cortical neurons to NMDA. It was noteworthy that the intracellular domain (ICD) of LRP1 was co-localized with TGN and furin. Furthermore, a furin inhibitor inhibited the cleavage of LRP1 and co-localization of LRP1-ICD with TGN or furin. Our findings suggest that furin-mediated cleavage of LRP1 and changes in the localization of LRP1-ICD were involved in the excitotoxic neuronal injury.

Highlights

Ischemic brain damage is associated with various deleterious events such as glutamate excitotoxicity, oxidative stress and trophic factor deficiency
As the lipoprotein receptor-related protein 1 (LRP1) precursor (~600 kDa) is cleaved by furin in the trans-Golgi network (TGN) to generate a 515-kDa α chain (LRP1-α-chain) and an 85-kDa membrane-anchored cytoplasmic β chain (LRP1-β-chain), we determined the amounts of α-chain and β-chain of LRP1 proteins after cerebral ischemia
The amount of α-chain of LRP1 was decreased (Fig. 1b,c), whereas that of a 17-kDa intracellular domain (ICD), which is produced by cleavage at an intramembrane site of LRP1, was significantly increased in the ischemic areas of the ipsilateral hemisphere after cerebral ischemia (Fig. 1b,e)

Summary

Introduction

Ischemic brain damage is associated with various deleterious events such as glutamate excitotoxicity, oxidative stress and trophic factor deficiency. It has been shown that cleaved ICD is transported into the nucleus where it contributes to transcriptional regulation of target genes. These findings raise the possibility that LRP1 and/or LRP1-ICD may contribute to the www.nature.com/scientificreports/. In this sense, we interestingly demonstrated earlier that furin participates in NMDA-induced neuronal death by acting upstream of calpain[16]. Pathophysiological changes in LRP1 and furin may possibly be associated with ischemic brain injury. We conducted experiments to determine changes in the processing pathway of LRP1 in a rat model of cerebral ischemia and by examining cultured cortical neurons after NMDA receptor-mediated excitotoxicity, which has been implicated in a variety of neurodegenerative diseases

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Conclusion