Neuroprotection by Neurotropin through Crosstalk of Neurotrophic and Innate Immune Receptors in PC12 Cells.

Yu Fukuda,Tatsuro Mutoh,Kazuki Nakajima

doi:10.3390/ijms21186456

Abstract

Infected or damaged tissues release multiple “alert” molecules such as alarmins and damage-associated molecular patterns (DAMPs) that are recognized by innate immune receptors, and induce tissue inflammation, regeneration, and repair. Recently, an extract from inflamed rabbit skin inoculated with vaccinia virus (Neurotropin®, NTP) was found to induce infarct tolerance in mice receiving permanent ischemic attack to the middle cerebral artery. Likewise, we report herein that NTP prevented the neurite retraction in PC12 cells by nerve growth factor (NGF) deprivation. This effect was accompanied by interaction of Fyn with high-affinity NGF receptor TrkA. Sucrose density gradient subcellular fractionation of NTP-treated cells showed heretofore unidentified membrane fractions with a high-buoyant density containing Trk, B subunit of cholera toxin-bound ganglioside, flotillin-1 and Fyn. Additionally, these new membrane fractions also contained Toll-like receptor 4 (TLR4). Inhibition of TLR4 function by TAK-242 prevented the formation of these unidentified membrane fractions and suppressed neuroprotection by NTP. These observations indicate that NTP controls TrkA-mediated signaling through the formation of clusters of new membrane microdomains, thus providing a platform for crosstalk between neurotrophic and innate immune receptors. Neuroprotective mechanisms through the interaction with innate immune systems may provide novel mechanism for neuroprotection.

Highlights

Neurotrophins control survival and differentiation of neurons through plasma membrane high-affinity receptor tropomyosin-related kinase (Trk) [1,2]
We have previously shown that NTP accelerates nerve growth factor (NGF) signaling which accompanies enhanced association of Trk with GM1 and possibly fucosyl-GM1 [25], an essential cofactor for Trk tyrosine kinasIent.[5J.]M. oBl.eSccai.u20s2e0,G21M, x1FOisR PaElsEoR RkEnVoIwEWn as a modulator of innate immune receptor Toll-like receptor 4 (TLR4) [27],5 of 14 we examined whether TLR4 has a role in the neuroprotective effects of NTP
Neuritogenic actions by NTP had been reported for the first time by Morita et al [29], where NTP enhanNceeusrniteougreitneicouactgtiroonwstbhyoNf PTCP1h2acdellbse.eInn rtehpeoprrteesdenfotrsttuhdeyf,irNstTtPimperebvyenMteodrintaeuertitael.re[2tr9a]c, twiohneirne PNCTtPrk ecnelhlsauncnedsernceounrditietioonustogfroNwGtFh-doefprPivCe1d2stcaetlelss.(FIingutrhee1)p. rIenseanptlascteubdoy-c, oNntTroPllepdr,edvoenutbelde-bnlienudreitde crleitnriaccatliotrniainl oPnCatrckutceelilsscuhnemdeirc csotrnodkieti,oinnstroafvNenGoFu-sdaepdrmivinedistsrtaattieosn(FoifgNurTeP1)f.oIrn1a5pdlaaycesbwo-acsoenfftreocltlievde, odnouthbeles-bulrivnidveadl, cilninfairccatl striziael,oendeamcuat,eaisncdhenmeuicrosltorogkicea,linsytrmavpetnoomussoafdtmheinpisattriaetniotsn[o3f0,N31T]P

Summary

Introduction

Neurotrophins control survival and differentiation of neurons through plasma membrane high-affinity receptor tropomyosin-related kinase (Trk) [1,2]. Nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), and NT-4, is capable of binding to a specific Trk receptor tyrosine kinase (TrkA, TrkB, and TrkC) and to the p75 low-affinity NGF receptor [3,4]. Lipid rafts for TrkB signaling are formed transiently and dynamically upon binding of its ligand BDNF [14] and are positively regulated by Fyn, a member of the Src-family kinases residing in lipid rafts [15]. In subsequent studies using rat pheochromocytoma PC12 cells overexpressing Trk (PCtrk cells) [24], NTP was shown to facilitate the TrkA-mediated neurotrophin signaling pathway [25]

Methods

Results

Conclusion