Neuroplastin Modulates Anti-Inflammatory Effects of MANF

Takuya Yagi,Fumihiko Urano,Maria Lindahl,Ave Eesmaa,Mart Saarma,Rie Asada,Kohsuke Kanekura

doi:10.2139/ssrn.3589833

Abstract

Endoplasmic reticulum (ER) stress plays a crucial role in the pathogenesis of various common diseases, such as diabetes mellitus and neurodegenerative disorders, as well as rare inherited diseases including Wolfram syndrome. ER stress is known to induce pro-inflammatory response and ultimately leads to apoptotic cell death. Mesencephalic astrocyte-derived neurotrophic factor (MANF) is an ER-localized protein whose expression and secretion is induced by ER stress, which in turn alleviates ER stress and inflammation. Although multiple studies have shown its therapeutic values in treatments of ER stress-related diseases, the underlying mechanism how MANF exerts its cytoprotective activity remains unclear due to the lack of knowledge of its receptor. Here we show that MANT binds to Neuroplastin (NPTN) on cell surface and mediates MANF-mediated suppression of inflammation. Biochemical analysis shows the physiological interaction between MANF and NPTN on the cell surface. The affinity of MANF to NPTN is higher than that of other related neurotrophic factors, including BDNF and GDNF. Overexpression and knockdown experiments show that NPTN induces inflammation through regulation of the NF-kB signaling pathways. MANF mitigates the inflammatory response and apoptosis mediated by cytokine stimulation or ER stress, and the effects of MANF are abrogated in NPTN deficient cells. Collectively, our results demonstrate that NPTN is a novel cell surface regulator for MANF which modulates inflammatory responses and cell death.

Highlights

The endoplasmic reticulum (ER) participates in many important cellular processes
NPTN knockdown by short hairpin RNA in HeLa cells significantly reduced the signal of the cells labeled by fluorescein isothiocyanate (FITC)-streptavidin (Figures 1D–1F), suggesting that Mesencephalic astrocyte-derived neurotrophic factor (MANF) interacts with NPTN in vivo
Because cerebral dopamine neurotrophic factor (CDNF) has a structural similarity with MANF, we tested the ability of CDNF to bind NPTN using microscale thermophoresis

Summary

Introduction

The endoplasmic reticulum (ER) participates in many important cellular processes This includes the native folding, post-translational modification, and trafficking of transmembrane and secretory proteins. The UPR maintains ER homeostasis through three distinct physiological responses: (1) translational attenuation to decrease the demands made on the organelle (Harding et al, 2002), (2) the transcriptional induction of genes encoding ER-resident chaperones to facilitate protein folding (Li et al, 2000; Yoshida et al, 1998), and (3) ER-associated degradation (ERAD) to degrade unfolded or misfolded proteins in the ER lumen (Ng et al, 2000; Travers et al, 2000). Excessive and unresolved ER stress induces pro-inflammatory response and eventually leads to apoptotic cell death, which contributes to the pathogenesis of a variety of diseases including neurodegenerative disorders and diabetes mellitus (Nakagawa et al, 2000; Urano et al, 2000)

Results

Discussion

Conclusion