信号转导2-生化课05课件

Signal-TransductionPathways(II)

2005－12珠海ImportantrolesofbiosignalingFunctionalintegrationofdistantorgans, tissuesandcellsrequirescommunication;Signalingisaprimalrequirementtorespondto ourenvironment;Thefoundationofanycomplexresponse pathwaylieswithcellularbiochemicals.Question:Howaretheyregulated?SopEPKB/AktRac,CDC42PTKPI-3K

R调理后吞噬病原侵袭死亡信号生存信号细胞凋亡和粘膜屏障损坏细胞存活细胞凋亡是由：

细胞内“死亡/生存”信号之间的精密平衡来决定干扰该平衡就可改变病原对细胞凋亡的最终影响Complicated“cross-talk”betweenbio-signalsPARTⅠ1Basiccharacteristicsofsignaltransduction2FourgeneraltypesofsignaltransducersPARTⅡ1Regulatorymechanisms2SomediseasescausedbydefectsinthebiosignalingpathwaysRegulatorymechanismsofBio-signals3.1Phosphorylationasaregulatorymechanism3.2Regulationoftranscriptionbysteroidhormones3.3RegulationofthecellcyclebyproteinkinasesRegulationofSignalingPathwaysExternalsignalsSecondmessengersModulatorproteinsFunctionTargetproteinsHormonescAMPOdorants

cGMPDrugsCa2+LightDAG IP3Mitogenichormones TyrosineGrowth kinasesfactorsproteinkinaseAndphosphatasestructuralproteinsAndenzymesmetabolicorphysiologicalresponsesPlasmamembranePhosphorylation&de-phosphorylationarethemostcommonregulatorymechanisms,mediatedbyproteinkinaseandphosphatase,respectively

蛋白激酶

nNTPnNDP蛋白质蛋白质-nPi

nPi 蛋白磷酸酶

H2OcAMPPKAPhosporylatingcellularproteinsResponseActivationofGProtein–CoupledReceptorsSHCGrb2GEFRas-GTPFRas-GDPFPiGAPSHCGrb2GEFRas-GTPFRas-GDPFPiGAPRas蛋白的上游和下游信号通路PI3K－AKT途径对细胞生存的调控机制TheNobelPrizeinPhysiologyandMedicine1994"fortheirdiscoveryofG-proteinsandtheroleoftheseproteinsinsignaltransductionincells"AlfredG.Gilman

1941-MartinRodbell

1925-1998Two-componentsystemorsignaling细菌的二元组分系统Ninfa等1986年首次报道了大肠杆菌营养信号转导的二元组分系统，大量的实验已经证实，二元组分系统是细菌信号转导的普遍机制。钝化蛋白活化蛋白

激素受体PIP2

磷脂酶C

PKCDAG

G－蛋白

IP3

细胞反应

Ca2+IP3敏感通道结合态IP3

内质网或液泡 细胞反应

Ca2+细胞内信号转导的双信使系统

PI3K－AKT途径对细胞生存的调控机制Mostofthesecomplicatedsignalingpathwaysaretransducedbythephosphorylationanddephosphoralationofsignalingprotein,regulatedbytheproteinkinasesandphosphatses蛋白磷酸酶proteinphosphatase，PP蛋白磷酸酶的分类与蛋白激酶相对应，分为丝氨酸/苏氨酸型蛋白磷酸酶和酪氨酸型蛋白磷酸酶。有些酶具有双重底物特异性对蛋白磷酸酶的研究还不如蛋白激酶那样深入。但两者的协同作用在细胞信号转导中的作用是不言而喻的。

PhosphorylationasaRegulatoryMechanismSignaltransductionAlteredkinaseactivitycGMPcAMPInsulinCa2+kinase

Thereare120kinasesinyeast–i.e. 2%oftheirentiregenomeSomekinasesarelocalizedtodiscretesubcellularregionsthatareincloseproximitytothespecifictargetprotein;Mechanismsbywhichhormones,retinoids,andVit.DregulategeneexpressionHormone(H),carriedtothetargettissueonserumbindingprot,diffusesacrossthePMandbindstoitsspecificreceptorprotein(Rec)inthenucleus.HbindingchangestheconformationofRec;formshomoorheterodimersandbindstospecificRregionscalledhormoneresponseelements(HREs)intheDNAadjacenttospecificgenesBindingregulatestranscriptionoftheadjacentgene(s),increasingordecreasingtherateofmRNAformation.Alteredlevelsofthehormoneregulatedgeneproductproducethecellularresponsetothehormone3.3.1ThecellcycleWhatiscellcycle?

Aprocessofcellularreproduction

CellcycletransitsorderlyandirreversiblyCellcycletransitsorderlyandirreversiblyThecompletionofonephaseisrequiredforthebeginningofthenext.Periodicactivationofspecificcyclin-Cdk

complexesAcycleofproteindestruction

eliminatesproteinsusedintheprecedingphaseaswellasproteinsthatwouldinhibitprogressionintothenextphase.Cyclin-dependentkinases(Cdks)Cdksdrivecellcycleprogression

byphosphorylatinga

groupofsubstrates

-Cdkspresentauniquepatternofactivityineach

phaseofthecellcycle Cdk1(Cdc2) Cdk2 Cdk3 Cdk4Cdk5 Cdk6 Cdk7G1G2,MLateG1,SG1,S,G2,MRegulationofCdksactivity

Cyclin:Activatingsubunit.

CyclinswerenamedbecauseoftheircyclicexpressionduringthecellcycleMitogenStimulationFourmechanismsregulateCDKactivity:1phosphorylationordephosphorylation,2controlleddegradationofcyclinsubunit,3periodicsynthesisofCDKsandcyclins,4actionofspecificCDKinhibitingproteins.RegulationofCdksactivity

Phosphorylationanddephospho.inCdk1

Activatingphosphorylationsite:Thr161Inhibitoryphosphorylationsite:Thr14,Thr15PPGrowthcontrollingsignalsareconveyedbystimulatoryorinhibitorypathwayssometargetproteinsofCDKs:Laminin-BreakdownofnuclearenvelopebeforesegregationofsisterchromatidsinmitosisispartlyduetoPi-lamininbyCDKActinmyosincontractilemachinery----InvolvedinpinchingadividingcellintotwoequalpartsduringcytokinesisRetinoblastomaprotein,pRb--participatesinamechanismthatarrestscelldivisioninG1CDKsRegulateCellDivisionbyPhosphorylatingCriticalProteins3.3.3Oncogenes,TumorSuppressorGenes(TSGs),andProgrammedCellDeathOncogenes:encodedefectivesignalingproteins(e.g.,growthfactors,receptors,Gproteins,proteinkinases,ortranscriptionregulators),continuallygivingthesignalforcelldivision;TSG:encoderegulatoryproteins;normallyinhibitcelldivision;mutationsinthesegenesaregeneticallyrecessiveCancer:theresultofanaccumulationofmutationsinoncogenesandTSGs.Oncogene-encodeddefectiveEGFreceptorFromnormalepithelialcelltocancerSummary

FourbasiccharactersofbiosignalsFourschemesofintercellularsignalingFourgeneraltypesofsignaltransducers gatedionchannels; receptorenzymes; G-proteincoupledreceptors SteroidReceptorsGproteins:Heterotrimeric&monomeric; ActivationanddeactivationmechanismsMajorsecondmessengers:cAMP,IP3,DAG,Ca2+,cGMP.Usinganexampletoexplainthecascadeofevents:asinglemoleculeofhormoneactivatescatalystthatinturnactivatesanothercatalyst,andsoon,resultsinsignalamplificationandcellresponseThecellcycleanditsregulationOncogenes,TSGs,andCancerPARTⅠ1Basiccharacteristicsofsignaltransduction2FourgeneraltypesofsignaltransducersPARTⅡ1Regulatorymechanisms2Somediseasescausedbydefectsinthebiosignalingpathways信号转导异常的原因和机制一、信号转导异常1.生物学因素：干扰细胞内信号转导通路:如霍乱毒素2.理化因素：电离辐射或机械刺影响信号转导成分而致癌3.遗传因素：信号蛋白数量/功能改变（突变）4.免疫学因素：刺激型和阻断型抗受体抗体5.内环境因素二、信号转导异常的发生环节V2RGsACcAMPATPPKAADHH2OH2O配体、受体或受体后信号通路的任何一个环节出现障碍都会影响到最终效应，使细胞增殖、分化、凋亡、代谢或功能失常，并导致疾病。以尿崩症为例ADH作用的三个环节异常均可导致尿崩症：

ADH分泌减少中枢性尿崩症

ADH-V2受体变异肾小管上皮细胞水通道蛋白（AQP2）异常集合管上皮细胞对ADH的反应性降低家族性尿崩症不同受体介导的信号转导通路存在cross-talk

并非所有的信号转导蛋白异常都能导致疾病细胞信号转导异常与疾病受体、信号转导障碍与疾病受体数量减少受体亲和力降低受体阻断型抗体的作用协同因子或辅助因子缺陷受体功能缺陷受体后信号转导蛋白缺陷特定信号转导过程减弱或中断激素抵抗征雄激素受体缺陷与雄激素抵抗征原因和机制：AR减少或失活突变男性假两性畸形特发性无精症症延髓脊髓性肌萎缩胰岛素受体与胰岛素抵抗性糖尿病1.遗传性胰岛素受体异常，包括受体的 合成减少 与配体的亲和力降低，如Arg735突变为Ser TPK活性降低，如Gly1008

突变等2.自身免疫性胰岛素受体异常 血液中存在抗胰岛素受体的抗体二、受体、信号转导过度激活与疾病某些信号转导蛋白过度表达某些信号转导蛋白组成型激活突变刺激型抗受体抗体生长激素（GH）分泌过多的垂体腺瘤中，～30%是由于编码Gsα的基因突变所致，从而抑制了GTP酶活性，使Gsα处于持续激活状态，cAMP含量增多，垂体细胞生长和分泌功能活跃。通路过度激活如肢端肥大症和巨人症霍乱毒素选择性的催化Gsα亚基上的Arg201核糖化，使GTP酶活性丧失，不能将GTP水解成GDP，从而使Gsα处于不可逆激活状态,不断刺激AC生成cAMP,胞浆中的cAMP含量可增加至正常的100倍以上，导致小肠上皮细胞膜蛋白构型改变，大量Cl-和水分子持续转运入肠腔，引起严重腹泻和脱水。肠腔GsCT霍乱(Cholera)ACcAMP↑↑↑Cl-H2ONa+CT：CholeraToxin三、多环节信号转导异常与疾病㈠肿瘤1.促细胞增殖的信号转导过强 ⑴生长因子产生增多 ⑵受体的改变 生长因子受体表达异常增多 突变使受体组成型激活⑶细胞内信号转导蛋白的改变 如Ras突变2.抑制细胞增殖的信号转导过弱生长抑制因子受体减少、丧失受体后信号转导通路异常细胞的生长负调控机制减弱或丧失GEF：GuaninenucleotideExchangeFactorGAP：GTPaseActivatingProteinActivationofRasproteinGEF：GuaninenucleotideExchangeFactorGAP：GTPaseActivatingProteinMutationofRasledtoitsconstitutiveactivationRho蛋白在肿瘤进展过程中的作用Tobe,ornottobe,thatisaquestion!Apoptosisisatightlyregulatedprocess.1.Theshiftofbalancebetweendeath&survivalsignalsdeterminedthecellfate(命运）2.Usuallyrequiredanumberofevents(orgenes)tocontrolapoptosisE.g.,activationofoneoncogenesinduceapoptosisinmostcases,inhibitapoptosisonlywiththesuppor