生化信号转导1－生化

Signal-TransductionPathways

信号转导通路(1)

郑利民2008珠海

zhenglm@1.干细胞的分化2.植物的生长发育是在环境因子的影响下正确进行时空表达的过程3.信号受体反应:手触摸就是刺激(信号)，小叶合拢就是反应。偶联刺激到反应之间的生化和分子途径,就是这个反应的信号转导通路触摸含羞草后,小叶合拢4.细胞信号转导网络的简单模式（信号输入）（信号输出）5.ImportantrolesofbiosignalingFunctionalintegrationofdistantorgans,tissuesandcellsrequirescommunication;Signalingisperhapsaprimalrequirementtorespondtoourenvironment;Thefoundationofanycomplexresponsepathwaylieswithcellularbiochemicals.BiosignalingIntercellular（细胞间）&Intracellular（细胞内）6.常见四种类型：Endocrine(内分泌）Paracrine(旁分泌）Autocrine(自分泌）MembraneattachedproteinIntercellularsignaling

（细胞间信号）7.Fourschemesofintercellularsignaling(1)8.Fourschemesofintercellularsignaling(2)9.Intracellularsignaling

（细胞内信号）10.IntracellularReceptor11.Electron-micrographofmacrophage(pink)attackingEscherichiacoli(green)12.M吞噬处理入侵细菌及提呈抗原的机制13.SignalTransductionPathway:Complicated14.FcR

CR3Ca++srcPI3kPKCMAPKRhoGTPasegelsolinArp2/3PLCPLDActinrearrangementPhagocytosis;OxidativeactivationSignals

forphagocytosisSignalReceptorAmplificationTransductionResponsessecondmessengers15.信号转导要素：信号或配体,受体,信号放大(产生第二信使),应答和反馈调节胞外 质膜 胞内16.PARTⅠ1Basiccharacteristicsofsignaltransduction2FourgeneraltypesofsignaltransducersPARTⅡ1Regulatorymechanisms2Somediseasescausedbydefectsinthebiosignalingpathways17.1Fourbasiccharacteristics:1.1Specificity1.2Amplification1.3Desensitization/Adaptation1.4Integration18.SpecificitySignalmoleculefitsbindingsiteonitscomplementaryreceptor;othersignalsdonotfit.thrombin19.Scatchardanalysisquantifiesthereceptor-ligandinteraction20.oftenshort-lived&lowconcentration21.Desensitization/Adaptation

ReceptoractivationtriggersafeedbackcircuitthatshutsoffthereceptororremovesitfromthecellsurfaceProducearapidandmajorcellularresponsetoatransientsignal22.IntegrationWhentwosignalshaveoppositeeffectsonametaboliccharacteristicsuchasconcentrationofasecondmessengerX,orthemembranepotentialVm,theregulatoryoutcomeresultsfromtheintegratedinputfrombothreceptors23.细胞存活细胞凋亡Thebalancebetweenpro-andanti-apoptoticgenes/signalsdeterminethecellfate细胞接受到“死亡信号”，不一定就会死亡若同时也接受到“生存信号”，就可继续存活24.25.2.Fourtypesofsignaltransducers2.1GatedIonChannels

2.1.1Ligand-gatedionchannels 2.1.2Voltage-gatedionchannels2.2ReceptorEnzymes2.3GProtein–CoupledReceptors andSecondMessengers2.4SteroidReceptors26.Fourgeneraltypesofsignaltransducers27.WhyIonChannels?Restingpotential:Asymmetricion-distributionActingpotentialGatedIonChannels

Ligand-gatedionchannels Voltage-gatedionchannels28.Restingpotential29.IonConc.inMammalianCellsandSerum(mM）IonCytoplasmBloodSerumK+1404Na+12145Cl-4116proteincharges1389Mg+20.81.5Ca+2<0.00021.8WhyIonChannels:asymmetricion-distribution30.asymmetricion-distributionRestingpotential31.pumpandionleakchannelsCl

-leakchannel32.Actingpotential33.ActingpotentialVoltage-gatedNa+channels&K+channelsLigand-gatedionchannel:Bindingofsomesmallmoleculeforcesanallosterictransitioninprotein,open/closechannel.

acetylcholine(乙酰胆碱)receptorionchannel2.1.2Voltage-gatedionchannelAchargedproteindomainmovesrelativetothemembraneinresponsetoachangeintransmembraneelectricalpotential.

(voltage-gatedNa+，

Ca2+，K+channels)35.乙酰胆碱受体离子通道1AchACh36.BindingofAChtoRcauseconformationalchange.AsM2helicestwistslightly,theLeuresidues(yellow)rotateawayfromthechannelandarereplacedbysmallerpolarresidues(blue).Thisgatingmechanismopenschannel,allowingpassageofCa,Na,orK乙酰胆碱受体离子通道2Closed Open37.Voltage-gatedNa+channels138.Voltage-gatedNa+channels239.2.Fourtypesofsignaltransducers2.1GatedIonChannels

2.1.1Ligand-gatedionchannels 2.1.2Voltage-gatedionchannels2.2ReceptorEnzymes2.3GProtein–CoupledReceptors andSecondMessengers2.4SteroidReceptors40.

2.2ReceptorenzymesAligand-bindingdomain(胞外)andanenzymeactivesiteoncytosolicside,connectedbyasingletransmembranesegment.CommonlyakinasethatphosphorylatesTyrresiduesinspecifictargetproteins（insulinreceptor）Other:synthesizethei.c.secondmessengercGMPinresponsetoex.c.signals

(thereceptorforatrialnatriureticfactor)41.Activationofreceptortyrosinekinases42.InsulinreceptortyrosinekinaseInsulinstructure43.Insulinreceptorbindsinsulinandundergoesautophosphorylationonitscarboxyl-terminalTyrresidues.InsulinreceptorphosphorylatesIRS-1onitsTyrresidues.SH2domainofGrb2bindstoP–TyrofIRS-1.SosbindstoGrb2,thentoRas,causingGDPreleaseandGTPbindingtoRas.ActivatedRasbindsandactivatesRaf-1.Raf-1phosphorylatesMEKontwoSerresidues,activatingit.MEKphosphorylatesERKonaThr&aTyrresidue,activatingit.ERKmovesintothenucleusandphosphorylatesNucleartranscriptionfactorssuchasElk1,activatingthem.PhosphorylatedElk1joinsSRFtostimulatethetranscriptionandtranslationofasetofgenesneededforcelldivision.44.Activationofglycogensynthasebyinsulin45.Regulationofbloodglucoselevel46.

ReceptorforatrialnatriureticfactorTwotypes(isozymes)ofguanylylcyclasethatparticipateinsignaltransduction.47.2.Fourtypesofsignaltransducers2.1GatedIonChannels

2.1.1Ligand-gatedionchannels 2.1.2Voltage-gatedionchannels2.2ReceptorEnzymes2.3GProtein–CoupledReceptors andSecondMessengers2.4SteroidReceptors48.2.3GPCRandSecondmessengersThreeessentialcomponents:1.aplasmamembranereceptorwithseventransmembranehelicalsegments2.anenzymeintheplasmamembranethatgeneratesanintracellular2ndmessenger3.aguanosinenucleotide–bindingprotein(Gprotein)49.ThreeessentialcomponentsofGProtein–CoupledReceptors50.51.AproteinbindsGuaninenucleotides(GDP,GTP);activatedinGTP-form,inactivatedinGDP-formIntegralmembraneprotein,heterotrimers();Havesimilar&subunits,butdifferin-subunitWhenG-proteinisactivated,thesubunitdissociatestointeractwithanenzymesthatgeneratesecondmessengers(e.g.cAMP)Others:smallG-proteins(~20-25kDa),e.g.Ras,Rho,Rac,etc,arenotmembranebound.Gprotein(GTP-bindingprotein)52.Gprotein(discovery)M.Rodbell:atransducerprovidedthelinkbetweenreceptorandamplifier.A.G.Gilman:identify&purifytheGprotein.System:MutatedlymphomacellscontaininganormalreceptorandcAMP-generatingenzyme,wasyetunabletorespond(producecAMP),sinceitlackedthetransducermutatedcellnormalcell53.NobelPrizeinPhysiologyandMedicine1994"fortheirdiscoveryofG-proteinsandtheroleoftheseproteinsinsignaltransductionincells"AlfredG.Gilman

1941-MartinRodbell

1925-199854.“ON-OFF”switchisregulatedbyGTPorGDPboundform.AllG-proteinshasintrinsicGTPaseactivity,releasePiandinactivated.Activation:releaseofGDPandreplacedbyGTP55.Twomajorsystems:2.3.1THEPKASYSTEM (cAMPasthesecondmessenger)

The-AdrenergicReceptorSystem2.3.2THEPKCSYSTEM

(DAG,IP3andCa2+asthesecondmessengers)56.TheassociationofactiveGs

withadenylylcyclasestimulatesthecyclasetocatalyzecAMPsynthesisAdenosine3’,5’-cyclicmonophosphate(cAMP)57.synthesizedinadrenalmedulla;belongstocatecholamines(儿茶酚胺）;targetcellsincludeliver,skeletalmuscle,heartmuscleandadipose;releasedinresponsetoacutestressEpinephrine肾上腺素signal58.Epinephrine肾上腺素signalingpathwaycAMP59.Epinephrine肾上腺素signalingpathway(2)60.ActivationofcAMP-dependentproteinkinase(PKA)InactivePKA:Regulatory(R)subunits:auto-inhibitorydomainsburiedcatalytic(C)subunits:substrate-bindingsitesblockedbyRsubunitsRsubunits:autoinhibitorydomainsburiedActivePKACsubunitsopensubstratebindingsites61.AcatalyticsubunitofPKAATPPotentinhibitorpeptide(PKI):Arg-Arg-Gln-Ala-Ile(consensussequencerecognizedbyPKAexceptAla)62.Epinephrinetriggersaseriesofreactionsinhepatocytesinwhichcatalystsactivatecatalysts,resultingingreat“amplification”ofthesignalx分子10,000x分子63.PKAregulatesanumberofenzymesTheproteinsphosohorylatedbyPKAsharearegionofsequencesimilarityaroundtheSerorThrresiduethatundergoesphosphorylation,asequencethatmarksthemforregulationbyPKA.ThecatalyticsiteofPKAinteractswithseveralresiduesneartheThrorSerresidueinthetargetprotein,whichdefinethesubstratespecificity.64.65.DesensitizationofthePKAsystem1desensitizingβ-AdrenergicReceptor2degradingthesecondmessager66.GsbgrecruitsbARKtothemembrane,whereitphospho-

SerattheC-terminusofRecpt.barrbindstothepi-C-terminusofRecpt.Receptor-arrestincomplexentersthecellbyendocytosis.67.β-Arrestinuncouplesr