神經(jīng)生物學：神經(jīng)營養(yǎng)因子

Chap16NeurotrophicFactor

神經(jīng)營養(yǎng)因子

HistoryItwasknownthatextracellularsignalscanpromotethegrowthanddifferentiationofnervecellsinmorethanhalfacenturyago.Nervegrowthfactor(NGF)wasfirstdiscoveredbyBuekerin1948.RitaLevi-MontalciniandVictorHamburgerdemonstratedNGFisnecessaryforsympatheticandsensoryneuronsNGFtokeeptheirsurvival.Neurite(神經(jīng)突起)Neuriticbranchisdescribedaxonanddendrite.Especially,itisavailableforgrowingneuritewhichdidnotassuredaxonordendrite.TheeffectofNGFonculturedspinalneurons(Levi-MontalciniR.1987.Science237:1157)Neurotrophicfactor(NTF)influencesthegrowth,differentiationandsurvivalofneuronsduringdevelopment.NTFsarealso

re-activatedinadulthoodintissuerenewalorregeneration.ThesignalingfailureofNTFmayunderlieneurodegenerativedisorderssuchasAlzheimerdisease(AD),Parkinsondisease(PD),huntingtondisease(HD)andamyotrophiclateralsclerosis(ALS).ThetermofNeurotrophicfactorThetermNeurotrophicFactorreferstoanymoleculethataffectsthenervessystembyinfluencingthegrowth,differentiation,orcellcyclesofneuronsorglia.

ThedifferencebetweenofNTFsandNeuropeptides:1)NTFsarelargemolecularproteins,butneuropeptidesarethesmallmolecularproteins(<30-40peptides).2)Differencemolecularsignalingpathway.

ThedifferencebetweenofNTFsandnonpeptides:NTFsaredistinguishedfrommanynonpeptidemolecules,includingsteroidhormones,retinoicacidandneurotransmitters,thatalsocaninfluencethegrowthandintegrityofthenervoussystem.

NPNTFThelifecyclesofNTFBiosynthesis

：synthesizedmainlyinthenervalcellbody,includingneuronandglia.Storage：storedinthelargedensecorevesicles,andwastransportedtonerveterminalorextendeddendrite.ThelifecyclesofNTFRelease：

SomeNTFs,includingBDNFandGDNF,wereproducedfromimmediate-earlygenes,therefore,theirreleasewasdependonactive-dependentsynthesis.Theothersweredependontheirdepolarization.Breakdown：

BrokendownbymembranepeptidasesBDNFwasdetainedbyfunctional-inactivereceptorandthenitsdispersionwasbaffled.Simultaneitythepersistence-actionwindowwasalsorestricted.Thepartnershipofactivation-synthesisresultstoNTFshigh-complicatedformsinintercellularinformationofneuronsandglia.ModesofintercellularcommunicationsubservedbyNTFRetogradetransmission

Paracrinetransmission

AutocrinetransmissionAnterogradetramsmissionNTF與神經(jīng)肽的區(qū)別NTFNPMolecularweight

Synthesislarge，>14kDaNTFisproducedincellbody.small,<kDaNPisproducedincellbody

StoragelargedensecoredvesicleslargedensecoredvesiclesReleaseactive-dependentsynthesis.depolarization.electricstimulation,hyperpotassiumcauseddepolarization.Breakdownproteasehydrolyzation,detained

byinactivation-receptorproteasehydrolyzationSignalingThebindingtoTrkreceptorleadtomanyofthebiologiceffectsThebindingG-proteincouplereceptorandthesecondmessengerleadtothebiologiceffects.Actionsretograde,anterograde,autocrine,paracrinetransmission.anterograde,autocrine,paracrinetransmission.NTF與神經(jīng)遞質(zhì)的區(qū)別NTFClassicaltransmittersMolecularweightLarge,>14kDa<1kDaSynthesisproductedincellbodyproducedattheterminalStoragelargedensecoredvesiclesSynapticvesiclesReleaseactive-dependentsynthesis.depolarization.Low-frequencystimulationdepolarization.breakdownproteasehydrolyzation,enshroudbyincativation-receptorreuptake,re-use,SignalingthebindingtoTrkreceptorleadtomanyofthebiologiceffectsThebindingG-proteincouplereceptorandthesecondmessengerleadtothebiologiceffects.Actionretograde,anterograde,autocrine,paracrinetransmission.anterograde,autocrine,paracrinetransmission.actingas‘quick’transmitter.

NeurotrophicFactors Receptors

NeurotrophinsTrk（R-PTKs）

NGF、BDNF、NT-3、NT-4TrkA、TrkB、TrkC1 GDNFfamilyCoupledtoRetGDNF、neurturin、persephinGFR

1、GFR

2、nu-known CNTFfamilyCoupledtoJanuskinase（JAK）

CNTF、LIF、IL-6 GP130、CNTFR

、LIFR

Ephrins Eph(R-PTKs) EGFfamilyErbB(R-PTKs)EGF,TGF

,neuregulns2

OthergrowthfactorsR-PTKs Insulin,IGF,FGF,PDGF interleukinsandrelatedcytokinesIL-IRcoupledtoPS/TK,R-PTKIL-1,IL-2,IL-3,IL-5,TNF

,TNF

CoupledtoJAK,Relatedtop753TGFfamilyTGF

R-PS/TRs OthercytokinesCoupledtoJAK,R-PTKsinterferons(IFN

,

,

),m-CSF,gm-CSFCoupledtoJAKChemokinesGprotein-coupledreceptorsCCchemokines(IL-8)CC1-CC8RCXCchemokines(MIP,MCP)CXC1-CXC4RCX3Cchemokines(neurotactin) Cx3C1R 分類NeurotrophinsNeurotrophinsaresmallproteins.TheyproducetheirphysiologiceffectsbymeansoftheTrkreceptorfamily.Familymenbers：NGF、BDNF、NT-3、NT-4/5。EffectionssurvivalofneuronsPreventingtodeathofneuronsneurogenesisPromoteaxonsanddendritesgrowth.neuritePromoteneuriteofaxonsanddendrites.AnabolismEnhancethesizeofneuronalbody.differentiationProteinsarenecessaryforneuronaldifferentiation.RegulatingthetransmitionIncreasethesynthesisofneurotransmittors,neuropeptidesandtheirsyntheticalenzymesElectricalexcitabilityAltertheactivationandlevelofionchannelsNGFBDNFNT-3composingofaminoacides

1163disulfidebonds1193disulfidebonds1193disulfidebondsMW13kDa13kDa13kDadistributionWidelydistrubutionCNS,PNSandperipheraltissuesInCNS:

hypothalamus,cortex,hippocampusindeveloping;

Inperipheraltissues:BDNFmRNAwashighlyexpressedinmuscletissuesWidelydistrubutinCNS,PNSreceptorsTrkATrkBTrkCsignalingpathwayTrkreceptorsignalingpathway.CharacteristicofneurotrphinsNeurotrophinsreceptor——Trk-RTransmembrancereceptorGlycoproteinswhosemolecularweightrangefrom140to145kDa.DifferenttypesofTrk-RNeurotrophinsandreceptorsDistributionofTrkRinnervalcellsThemostofTrkAswerefoundinsensoryandsympatheticneurons,afewinbrainneurons.TrkBandTrkCexpressinthemostofneurons.Trktruncationwasexistedinastrocytesandoligodendrocytes.P75receptora75-kDaproteinasthelow-affinityneurotrophinreceptor.alsoappearstomodulateTrksignaling;theincreasesphosphorylationofTrkandthenenhancestheactivationofTrk.mayallowTrk-RtoresponsetothelessconcentrationofNGFandtheotherneurotrophinsIt’sbelievedtobeakeyplayerincelldeathpathways.ThesignalingpathwayofNeurotrophins

TrkwasactivatedbyautophosphorylationofTry(Y490、Y785)intheintracellulardomainandsubsequentlyformtodimer,andthenenablesphosphorylationtheintracellularsignalingproteinbyinteractingwithitsSH2domain,e.g.ShcandPLC

.Threesignalingpathways:Ras/MAPKcascadesPI3K/AKTPLC/IP3-dependentCa2+releaseIP3DAGCa2+釋放

ThesignalingpathwayofNeurotrophinsRas/MAPK

Rasprotein：①.21kDphosphorylatingprotein;asmallG-protein;

②

switchbetweeninactivationofGDP-boundformandactivationofGTP-boundform

③

GTP-boundformkeepstheactivationofcellgrowthandactivatesthecellstooverproliferationacascadeofTrkAactivatesRasShcSosRasGrb2AcascadeofRas/Raf/MEK/ERKRafERKTheeffectofRas/Raf/MEKcascadeinneuritegrowthPC12originatesfrompheochromocytomaTrkAandp75areexpressedinmembraneofPC12NGFtreatmentmaystimulatetheneuritegrowthonPC12cells.TheeffectofRas/Raf/MEKcascadeinneuritegrowthDiseaseofRassignalingpathwayDefectsoftheintracellularsignalingpathways,whichwereactivatedbyNTFs,canleadtotheoverproliferationofcells,subsequentlygiverisetovariousdisorders.NeurofibromatosisisaninheriteddiseasecausedbymutationoftheRas-modulatoryprotein.OncogenicRasgeneisamutationformthatcauseRastoremaininitsactivestatebytwoRasforms:1)reducedtheintrinsicGTPaseactivityofRas;2)inhibitedthesensitivityofRastoGAPs(GTPaseactivatingproteins).NeurotrophinsandTrk-Rknockoutmice

Mice,inwhichthegenesencodingNGForTrkAhavebeeninactivated,showedalossofsympatheticneuronsaswellassensoryneuronsindorsalrootgangliaofthetrigeminalsystem.NGForTrkAKOmicealsoshowedpartiallossofthecholinergicneuronsinthebasalforebrainthatprojecttothehippocampusandcerebralcortex.TrkBKOmiceshowedthedeathofcranialmotorneuronsandtrigeminalganglionneurons.BDNFKOmiceshowednoalossoffacialorspinalmotorneurons.Incontrast,TrkBKOmiceshowedsignificantmotorneuronsloss.TheeffectsofNeurotrophinsNGFactivatedneuritegrowth.BDNFmaintainssurvivalofmotorneurons.NT-4isimportantforsupportingsurvivalofmotorneuronsindevelopment.TheeffectofNT-3,maintainingsurvivalofmotorneurons,islessthanBDNFandNT-4.TheeffectsofNGFFasteffect:Regulatingorparticipatinginthereleaseofneurotransmitter：alteringtheactivationofionchannels；enhancingthesynthesisoftransmitters,peptidesanditssyntheticalenzymes.Sloweffect:Preventingagainstdeathofneurons；

Maintainingdevelopmentofsympatheticneurons;Maintainingneuronalfunctionandplasticityinadult.Topromotesurvivalofcholinergicneurons:TopromotesurvivalofneuronsAsthesameofNGF,BDNFalsocanpromotesurvivalofcholinergicneuronsanddifferentiationoftheirphenotypeinvitro.Butbotheffectindifferentgrowthphasesofcholingergicneurons,BDNFinforepartbutNGFinanaphase.BDNF、NT-3andNT-4canpromotesurvivalofsomemotorcorticalneuronsandhippocampalneurons.NeurotrophinscanpromotesurvivaloftheneuronsofNE-activated,DA-activated,5-HT-activatiedinbrainstem.ToregulatesynapticplasticityStudiesoftheformationofoculardominancecolumnsinthedevelopingvisualcortexhavebeconfirmedthatneurotrophinsmediateformsofsynapticplasticity.Neurotrophinsalsoareinvolvedinregulatingsynapticplasticityinthefullydifferentiatedadultbrain.Neurotrophinscanmodulatesynaptictransmissionandregulatetheformationandstrengtheningofsynapses.Neurotrophinsalsoregulatesynaptictransmissioninthehippocampus,althoughsuchaccountsremaincontroversy.GDNFFamilyGDNFwasfirstisolatedfromaglialcelllinethatmaintainssurvivalofdopaminergicneuronsformthemidbraininculture.Glialcellline-DerivedNeurotrophicFactorGDNF,aglycosylatedproteinof18kDa.GDNFfamilyincludesNeurturin、persphinGDNFreceptorsanditssignalingpathwayGDNFeffectsviatheactivationofaproteintyrosinekinase,butsuchactivationisachievedindirectlythroughaninterveningreceptorprotein.AGDNFdimerbindstoaspecificreceptor,termedGFR

1,aproteinof40kDa,whichisanchoredtotheplasmamembranebyGPI.GDNFbindingtriggersGFR

1tocombinewithRet.Retisatransmembraneproteintyrosinekinaseofabout150kDa.ThisbindingresultsinRettoactivate,whichisbelievedthatleadingtomanyofthebiologiceffectsofGDNFviatriggeringthephosphorylationofspecificsubstrates.Theautophosphorylatedc-Retinturnactivatesseveralintracellularsignalingproteinsthatregulatecellsurvival,differentiation,proliferation,migration,neuriticgrowthandsynapticmodulation.Thesesignalingproteins,belongingtoproteinandlipidkinasesandphospholipases,actonseveralsignaltransductionpathways.PLC-

Ca2+byincreasingthelevelofIP3MAPkinaseneuritegrowthneuronalsurvivalPI3KneuronalsurvivalneuritegrowthSeveralsignaltransductionpathways:GDNFmediatedc-RetsignalingcaninteractwithandactivatetheSrc-familykinaseselicitingoptimalneuriteoutgrowthandneuronalsurvival.InRetdeficientcelllinesandprimaryneurons,GDNFtriggersSrc-familykinaseactivationandphosphorylationofERK/MAPkinase,PLC-

andthetranscriptionfactorCREB,andinductionofFosGDNFfamilyreceptorscomplexTheeffectsofGDNFfamily1.DopamineNeurons

GDNFselectivelyenhancedthesurvivalanddevelopmentofdopaminergicneurons.Invitro,GDNFprotectedmesencephalicdopaminergiccellsagainstthedeleteriouseffectsoftheneurotoxinMPP1.GDNFimprovedthesurvivalofcells,preventedfurthercelldeath,andstimulatedtheregrowthofdopaminergicfibersdamagedbyMPP1.Invivo,

InPDmodelinducedbytheadministrationofthe6-OHDAintothemedialforebrainbundle,GDNFhasbeenshowntoreverseapomorphine-inducedrotationandrescuelesioneddopaminergicneuronsGDNFmaybeavaluabletherapeuticagentintreatingParkinson’sdisease.NeurturinisalsoafactorfortreatmentofPD.TheeffectsofGDNFfamily2.Motorneurons

GDNFwasshowntoprotectfacialmotoneuronsfrominjury-inducedcelldeath.GDNFcanaffectmotoneurondevelopmentandmotoneuronsurvivalafteraxotomy,novelapproachesformotorneurondiseasearesuggested.GDNFcanrescuesomespinalmotoneuronfromprogrammedcelldeathindevelopmentandpromoteitssurvival.GDNFcanpreventtheneuronaldegenerationwhichwascausedbyaxonbroken.TheeffectsofGDNFfamily3.PNSneurons

GDNF

promotesthesurvivalandneuriticoutgrowthofcultured

sympatheticneurons,parasympatheticciliaryganglion

neuronsandsensorydorsalrootganglionneurons.GDNFisimportantforthedevelopingofentericneuronsandrenalneurons.Ret(loss-of-function)mutationhasthesamesymptonashumanHirschsprungdesease.Ret(gain-of-function)mutationhasthesamesymptomasneuralcrestmaligntumor,e.g.multadenomatosis,medullarthyroidcancer.CNTFfamily(Ciliaryneurotriphicfactor)CNTFfamilyReceptors(JAK-coupledreceptors)CNTFGp130

LIFR

CNTFR

LIF(leukemiainhibitoryfactor)IL-6，prolactin,growthhormone,leptinIL-11、OSM(oncostatinM)

CNTFfamilyCNTF,aproteinapproximately24kDainsize,wasstudiedasasurvivalfactorforchickciliarygenglionneurons.CNTFisonesuchcytokinethatplaysaroleamongseveralprocesseswithinthehumanbodyfromendogenousneuroprotectiontoregulationofenergyexpenditure.CNTFisamult-functionalocytokine,expressedinglialcellsofperipheralnervesandCNS.ThefamilymembersincludeLIF,IL-6,OSM,IL-1,prolactin,growthhormone,leptin,andinterferons.CNTFreceptorcomplexConsistsofthreecomponents:

CNTFR

signaltransducingreceptorcomponent:

LIFR,gp130,TheeffectsofCNTFCNTFhasbeenproventoregulatethesurvivalordifferentiationofmanyneuronalcells,includingsympatheticneurons,sensoryneurons,motorneurons,culturedhippocampalneuronsanddopaminergicneuronsinthemidbrain.Itseffectonmotorneuronsareperhapsthemostframatic：CNTFnotonlysupportsthesurvivalofthesneuronsinvitro,italsopreventstheirdegenerationafteraxotomyandimprovessomemotordefectsinmurineofmotorneurondisease.LIFandIL-6mayregulatethesurvivalordifferentiationofneurons.IL-6promotesthesurvivalofseptalcholinergic,mesencephaliccatecholaminerfic,andhypothalamicneuronsinculture.CNTFandCNTFR

CNTFKOnicedevelopnormally,exhibitingonlymildmotorneurondefectsduringadulthood.Approximately2.5%oftheJapanesepopulationarehomozygousforinactivatingmutationsofCNTFandthustheyarehumanCNTF“knockouts”,likeCNTFKOmice.Incontrast,micelackingtheCNTFRlosealmostalloftheirmotorneuronsanddiewithin24hoursofbirth.

ItsuggestedtheexistenceofanotherendogenousligandforCNTFR,butthathasnotbeendiscoveredyet.TherapeuticagentsdirectedatNTFTreatmentwithBDNF,CNTF,orcombinationofthesefactorshasbeenshowntoslowdownorattesttheprogressionofmotorneurondegengrationinthewobblermouse.BecauseBDNF,GDNG,andotherfactorshaveenhancedthesurvivalo