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Nogo-A-Δ20/EphA4 interaction antagonizes apoptosis of neural stem cells by integrating p38 and JNK MAPK signaling

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Abstract

Nogo-A protein consists of two main extracellular domains: Nogo-66 (rat amino acid [aa] 1019–1083) and Nogo-A-Δ20 (extracellular, active 180 amino acid Nogo-A region), which serve as strong inhibitors of axon regeneration in the adult CNS (Central Nervous System). Although receptors S1PR2 and HSPGs have been identified as Nogo-A-Δ20 binding proteins, it remains at present elusive whether other receptors directly interacting with Nogo-A-Δ20 exist, and decrease cell death. On the other hand, the key roles of EphA4 in the regulation of glioblastoma, axon regeneration and NSCs (Neural Stem Cells) proliferation or differentiation are well understood, but little is known the relationship between EphA4 and Nogo-A-Δ20 in NSCs apoptosis. Thus, we aim to determine whether Nogo-A-Δ20 can bind to EphA4 and affect survival of NSCs. Here, we discover that EphA4, belonging to a member of erythropoietin-producing hepatocellular (Eph) receptors family, could be acting as a high affinity ligand for Nogo-A-Δ20. Trans-membrane protein of EphA4 is needed for Nogo-A-Δ20-triggered inhibition of NSCs apoptosis, which are mediated by balancing p38 inactivation and JNK MAPK pathway activation. Finally, we predict at the atomic level that essential residues Lys-205, Ile-190, Pro-194 in Nogo-A-Δ20 and EphA4 residues Gln-390, Asn-425, Pro-426 might play critical roles in Nogo-A-Δ20/EphA4 binding via molecular docking.

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All data generated or analyzed during this study are included in this published article.

Abbreviations

NSCs:

Neural stem cells

DHC:

Dehydrocorydaline chloride

SP:

SP600125

Rhy:

Rhynchophylline

GADPH:

Glyceraldehyde-3-phosphate dehydrogenase

CNS:

Central nervous system

SCI:

Control group: Con. spinal cord injury

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Acknowledgements

SWISS-MODEL is available from https://swissmodel.expasy.org/interactive software. ZDOCK is available from http://zdock.umassmed.edu/. Additionally, we must thank Dr Wei Lin, Jin of Shanghai Jiao Tong University for giving us suggestions of experimental design and Professor Li Fang, Zhang of Wenzhou Medical University for technical assistance in protein purification.

Funding

The study was supported by the Zhejiang Provincial Natural Science Foundation of China (Grant No. LY18H090013) and Wenzhou Municipal Science & Technology Bureau Fund (Grant No. Y20180094).

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Contributions

J-LW: Formal analysis, writing original draft. W-GC: formal analysis. C-JX: formal analysis, writing—original draft. J-JZ performed partial WB.

Corresponding author

Correspondence to Chao-Jin Xu.

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10735_2021_9960_MOESM1_ESM.tif

Fig.S1 Overall diagram of interaction between Nogo-A-Δ20 with EphA4. Cartoon structure of α-helix represents Nogo-A-Δ20. Brown sticks indicate residues of binding sites located in EphA4 ecodomain. LBD: ephrins ligand-binding domain. Fn1 and Fn2: 2 fibronectin-type-3 domains. (TIF 3768 kb)

10735_2021_9960_MOESM2_ESM.tif

Fig.S2 EphA4 knockdown inhibits anti-apoptosis functions of Nogo-A-△20 in NSCs. (A) NSCs were transfected with ctl-small interfering RNA (sictl) and EphA4-siRNA for 48 h, EphA4 expression at the protein were decreased compared with negative control (sictl) (n = 3, t-test,**p < 0.01 vs sictl). (B) After transfection for 48 h as described in (A), Nogo-A-Δ20 was added into culture medium for another 24h, supernatants of cell lysates were collected and blotted with proapoptotic proteins antibody: cleaved-PARP and caspase 3. (n = 3, ANOVA, **p < 0.01 vs con, ##p < 0.01 vs sictl). siRNA, small interfering RNA; siEphA4, EphA4 siRNA; siCtl, scramble siRNA. Quantification by densitometric scans was presented by apoptotic-related antibody/β-actin. Data were normalized to β-actin. n=3, Mean±S.D. **P < 0.01 vs siCtl group or control group, ##P < 0.01 vs. Nogo-A-Δ20+ siCtl group. Data were normalized to that of siCtl. (TIF 1108 kb)

10735_2021_9960_MOESM3_ESM.tif

Fig.S3 Effects of DHC and SP on NSCs apoptosis in vitro. NSCs were treated with 10 μM SP (A) and 10 μM DHC (B) for 48 h, cell extracts were collected and pro-apoptotic members like caspase 8, cleaved-PARP and p53 were detected by Western blotting. Representative data of three individual samples in SP group (C-E) and DHC group (F-H) were through statistical analysis of t-test. *P < 0.05 vs control group. Data were normalized to that of Control. NS: no significant difference. (TIF 620 kb)

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Wang, JL., Chen, WG., Zhang, JJ. et al. Nogo-A-Δ20/EphA4 interaction antagonizes apoptosis of neural stem cells by integrating p38 and JNK MAPK signaling. J Mol Histol 52, 521–537 (2021). https://doi.org/10.1007/s10735-021-09960-6

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  • DOI: https://doi.org/10.1007/s10735-021-09960-6

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