生物化學(xué)講稿 Cell Cycle and Sensory systems

1CellCycleand

SensorysystemsRespondingtoEnvironmentalChanges2別擠啦！再擠就……!Cancer:Anuncontrolledcellgrowththatbreachhomeostasis456細(xì)胞存活細(xì)胞凋亡Thebalancebetweenpro-andanti-apoptoticgenes/signalsdeterminethecellfate細(xì)胞接受到“死亡信號”，不一定就會死亡若同時也接受到“生存信號”，就可繼續(xù)存活7cellcycle:Aprocessofcellularreproduction8Fourphases:G1,S,G2,MGap(G1andG2)phases: Respondtoproliferativeandanti-proliferativesignals,synthesizeRNAandproteinSynthetic(S)phase:ReplicationofthechromosomesMitotic(M)phase:segregationofchromosomesandothercellconstituentsintotwodaughtercells9Cellcycletransitsorderlyandirreversibly10CellcycletransitsorderlyandirreversiblyThecompletionofonephaseisrequiredforthebeginningofthenext.Periodicactivationofspecificcyclin-CdkcomplexesAcycleofproteindestructioneliminatesproteinsusedintheprecedingphaseaswellasproteinsthatwouldinhibitprogressionintothenextphase.11Cyclin-dependentkinases(Cdks)Cdksdrivecellcycleprogressionbyphosphorylatingagroupofsubstrates -Cdkspresentauniquepatternofactivityineachphaseofthecellcycle Cdk1(Cdc2) Cdk2 Cdk3 Cdk4Cdk5 Cdk6 Cdk7G1G2,MLateG1,SG1,S,G2,M12RegulationofCdksactivity

Cyclin:Activatingsubunit.CyclinswerenamedbecauseoftheircyclicexpressionduringthecellcycleMitogenStimulation13FourmechanismsregulateCDKactivity:1phosphorylationordephosphorylation,2controlleddegradationofcyclinsubunit,3periodicsynthesisofCDKsandcyclins,4actionofspecificCDKinhibitingproteins.14Growthcontrollingsignalsareconveyedbystimulatoryorinhibitorypathways16Contents

PartI:Sensorysystems

17Olfaction--smellGustation--tasteVision--see,viewHearing--listenTouchingchangebyskinAllbasedonSignal-transductionpathwaysactivatedbytheenvironmentsFiveMajorSensorySystems18OlfactionDetectionofdifferentchemicalsinairLocation:MainOlfactory(Nasal)EpitheliumShapeofmoleculeisresponsiblefortheirsmellsFeatures:specific,detectavastarrayofodorantsOdorantsaredecodedbyacombinatorialmechanism19SpecificregionthatdetectodorantsAtthetopofnasalcavity,contains~106sensoryneurons.Nerveimpulsesgeneratedontheciliatravelfromsensoryneuronstoolfactorybulb纖毛20Moleculareventsofolfaction

Theseinteractionsoccurintheciliaofolfactoryreceptors(OR)

ORfamily–ASevenTMR

>1000geneinmouse,~500inhuman(mostofthemarepseudogenes)

21OdorantReceptor(OR)Blue:stronglyconservedRed:highlyvariablegreencylinders:7presumedTMhelicesThehighlyvariablecentralregion,(h4&5),issiteofodorantbinding,differsinORthatbinddistinctodorantmolecules.Eacholf.neuronexpressesonlyasingleORgeneamonghundreds,determinedatrandom22Chewinggums綠薄荷香菜Theshapeofmoleculeiscrucial(stereo-specific)2324PatternsofORactivationTestresponsesofdifferentOR.Coloredbox:OR(top)respondedtocompound(left)Darkercolors:ORactivatedatalowerconcentrationofodorantOneOdorantactivatesseveralOR;OneORisactivatedby>1odorantAsmallarrayofORdistinguishavastnumberofodorants25Taste-sensitive

areasoftongueFiveprimarytastes:BitterSweetSaltSourUmami

(Glutamate,delicious)2.TasteBack26DiverseSignalingPathwaysDetectingTastesBitterreceptorGustducinBitter&sweet:experiencedvia7-TMreceptorsactingthroughaspecialGprotein,Gustducin27Salty&sour:directlyviamembraneionchannels

Salt:detectedbypassagethoughsodiumchannelsSour:resultsfromtheeffectsofH+onvariouschannels.Umami:byamodifiedformofonebrainreceptorthatrespondstoglutamateasa

neurotransmitterDiversePathwaysDetectTastes(II)28Transductionforsweettastants29Differinggeneexpres.&connec.patternsinOR&TROR:eachneuronexpressesasingleOR,neuronsexpressingsameORconvergetospecificsitesinbrain.BR（苦味）eachneuronexpressesmanyBRgenes,sotheidentityofthetastantislostintransmission.Olfactionvs.Taste30Newfinding：FatReceptorJ.Clin.Invest.2005；115:2965-7TastebudandstructureofTRforfatCD36ontheapicalsurfaceoftastecells嚙齒動物偏好油味，特別是對長鏈脂肪酸(植物油等）。舌頭上的味蕾細(xì)胞的頂面存在CD36，可感受到飲食中的油味。該基因敲除后的小鼠不再對含油食物表現(xiàn)出偏好。油在鼠的口中就會引起膽汁和胰液分泌，以助消化；該過程需要CD36參與。若能理解為什么油脂食物如此美味，肯定有助于我們另尋妙方來攻克肥胖。313.Visionbasedontheabsorptionoflightbyphotoreceptorcells:cones,respondtobrightlightsandcolors,rods,onlytodimlight.Onlysensitivetovisiblelight(330-850nm)圓錐32Rhodopsin–photoreceptorinrodcell

a7－TMreceptor,complexofproteinopsin視蛋白

andchromophore11-cis-retinal.Absorptionoflightchangesstructureintoall-trans-retinal.Activationofrhodopsin視紫紅質(zhì)bylightNote:structuralchangeofretinal33Activationofrhodopsinbylight.Noticethestructuralchangeofretinal順式34Lightreceptioninthevertebrateeye35VisualsignaltransductionAbsorptionoflightchangesstructureintoall-trans-retinal,settinginmotionasignalingpathwaythatleadstobreakdownofcGMP,tohyperpolarization,thennerveimpulse.36Molecularconsequencesofphotonabsorptionbyrhodopsinintherodoutersegment37ColorVisionMediatedby3distinct7-TMphotoreceptorsthatemploy11-cis-retinalasachromophore;absorblightinblue,green,&redspectrumAbsorptionspectraoftheconevisualpigmentresponsibleforcolorvision.Blue(426),green(530)andred(560)384.HearingTolocatesoundsources,dependsontheabilitytodetecttimedelaybetweenthearrivalofasoundatoneearandtheotherbasedondetectionofmechanicalstimuliAmajorcluetothemechanismofhearingisitsspeedHightimeresolution-asshortas0.02ms39HairCellsUseaConnectedBundleofStereociliatoDetectTinyMotionsHaircellsHairbundleTiplinks40Modelforhair-celltransductionHairbundletiptowardthetallestpart,thetiplinkpullsonandopensanionchannelMovementintheoppositedirectionrelaxesthetensioninthetiplink,closeanyopenchannels.415.TouchTwokeycomponents:pressure&temperature

Nociceptors:specializedneuronstransmitsignals,interpretedbybrainaspainVR1(thecapsaicinreceptor),functionsasacationchannelthatinitiatesanerveimpulse“pain”vs“spicytaste”Capsaicinanditsreceptornoci:傷害capsaicin：辣椒素42Otherless-familiarsensorysystemsMagnetotactic:indirectionsdictatedbyEarth’smagneticfieldAbilitytorespondtochemicalsignalscalledpheromones,releasedbyotherpersonsSenseoftime,manifestedinourcircadianrhythmsofactivityandrestfulness；influencedbydailychangesinlightMagnetotacticbacteriumphero:信息circadian：生理節(jié)奏43Commonfeaturesofsignalings

thatdetecthormones,light,smells,andtastes抗利尿激素44SummaryforSensoryTransductioninVision,Olfaction,andGustationInvertebrates,theyemployserpentinereceptors,actthroughheterotrimericGproteinstochangetheVmofthesensoryneuronThereisahighdegreeofconservationofsignalingproteinsandtransductionmechanismsacrossspecies信號轉(zhuǎn)導(dǎo)異常的原因和機(jī)制一、信號轉(zhuǎn)導(dǎo)異常1.生物學(xué)因素：干擾細(xì)胞內(nèi)信號轉(zhuǎn)導(dǎo)通路:如霍亂毒素2.理化因素：電離輻射或機(jī)械刺影響信號轉(zhuǎn)導(dǎo)成分而致癌3.遺傳因素：信號蛋白數(shù)量/功能改變（突變）4.免疫學(xué)因素：刺激型和阻斷型抗受體抗體5.內(nèi)環(huán)境因素46二、信號轉(zhuǎn)導(dǎo)異常的發(fā)生環(huán)節(jié)V2RGsACcAMPATPPKAADHH2OH2O配體、受體或受體后信號通路的任何一個環(huán)節(jié)出現(xiàn)障礙都會影響到最終效應(yīng)，使細(xì)胞增殖、分化、凋亡、代謝或功能失常，并導(dǎo)致疾病。以尿崩癥為例ADH作用的三個環(huán)節(jié)異常均可導(dǎo)致尿崩癥：

ADH分泌減少中樞性尿崩癥

ADH-V2受體變異腎小管上皮細(xì)胞水通道蛋白（AQP2）異常集合管上皮細(xì)胞對ADH的反應(yīng)性降低家族性尿崩癥不同受體介導(dǎo)的信號轉(zhuǎn)導(dǎo)通路存在cross-talk

并非所有的信號轉(zhuǎn)導(dǎo)蛋白異常都能導(dǎo)致疾病48細(xì)胞信號轉(zhuǎn)導(dǎo)異常與疾病受體、信號轉(zhuǎn)導(dǎo)障礙與疾病受體數(shù)量減少受體親和力降低受體阻斷型抗體的作用協(xié)同因子或輔助因子缺陷受體功能缺陷受體后信號轉(zhuǎn)導(dǎo)蛋白缺陷特定信號轉(zhuǎn)導(dǎo)過程減弱或中斷激素抵抗征49雄激素受體缺陷與雄激素抵抗征原因和機(jī)制：AR減少或失活突變男性假兩性畸形特發(fā)性無精癥癥延髓脊髓性肌萎縮50胰島素受體與胰島素抵抗性糖尿病遺傳性胰島素受體異常，包括 受體的合成減少 與配體的親和力降低，如Arg735突變?yōu)镾er TPK活性降低，如Gly1008

突變等2.自身免疫性胰島素受體異常 血液中存在抗胰島素受體的抗體51二、受體、信號轉(zhuǎn)導(dǎo)過度激活與疾病某些信號轉(zhuǎn)導(dǎo)蛋白過度表達(dá)某些信號轉(zhuǎn)導(dǎo)蛋白組成型激活突變刺激型抗受體抗體生長激素（GH）分泌過多的垂體腺瘤中，～30%是由于編碼Gsα的基因突變所致，從而抑制了GTP酶活性，使Gsα處于持續(xù)激活狀態(tài)，cAMP含量增多，垂體細(xì)胞生長和分泌功能活躍。通路過度激活如肢端肥大癥和巨人癥52霍亂毒素選擇性的催化Gsα亞基上的Arg201核糖化，使GTP酶活性喪失，不能將GTP水解成GDP，從而使Gsα處于不可逆激活狀態(tài),不斷刺激AC生成cAMP,胞漿中的cAMP含量可增加至正常的100倍以上，導(dǎo)致小腸上皮細(xì)胞膜蛋白構(gòu)型改變，大量Cl-和水分子持續(xù)轉(zhuǎn)運(yùn)入腸腔，引起嚴(yán)重腹瀉和脫水。53腸腔GsCT霍亂(Cholera)ACcAMP↑↑↑Cl-H2ONa+CT：CholeraToxin54三、多環(huán)節(jié)信號轉(zhuǎn)導(dǎo)異常與疾病:腫瘤1.促細(xì)胞增殖的信號轉(zhuǎn)導(dǎo)過強(qiáng)

1).生長因子產(chǎn)生增多

2).受體：生長因子受體表達(dá)異常增多或/和突變激活

3).細(xì)胞內(nèi)信號轉(zhuǎn)導(dǎo)蛋白的改變,如Ras突變細(xì)胞周期失控：－腫瘤發(fā)生的必經(jīng)步驟破壞其調(diào)控機(jī)制：－形成腫瘤的先決條件細(xì)胞周期及其調(diào)控機(jī)制？2.抑制細(xì)胞增殖的信號轉(zhuǎn)導(dǎo)過弱生長抑制因子受體減少、喪失受體后信號轉(zhuǎn)導(dǎo)通路異常細(xì)胞的生長負(fù)調(diào)控機(jī)制減弱或喪失56Growthcontrollingsignalsareconveyedbystimulatoryorinhibitorypathways5758Oncogene-encodeddefectiveEGFreceptor59GEF：GuaninenucleotideExchangeFactorGAP：GTPaseActivatingProteinActivationofRasprotein60GEF：GuaninenucleotideExchangeFactorGAP：GTPaseActivatingProteinMutationofRasconstitutiveactivation62Oncogenes,TumorSuppressorGenes(TSGs),andProgrammedCellDeathOncogenes:encodedefectivesignalingproteins(e.g.,growthfactors,receptors,Gproteins,proteinkinases,ortranscriptionregulators),continuallygivingthesignalforcelldivision;TSG:encoderegulatoryproteins;normallyinhibitcelldivision;mutationsinthesegenesaregeneticallyrecessiveCancer:theresultofanaccumulationofmutationsinoncogenesandTSGs.Tobe,ornottobe,thatisaquestion!Apoptosisisatightlyregulatedprocess.1.Theshiftofbalancebetweendeath&survivalsignalsdeterminedthecellfate(命運(yùn)）2.Usuallyrequiredanumberofevents(orgenes)tocontrolapoptosisE.g.,activationofoneoncogenesinduceapoptosisinmostcases,inhibitapoptosisonlywiththesupportfromothersignals.(Togetherwestand,separatewedied)雙向調(diào)控基因—c-Myc的作用模型65腫瘤形成必須是在單個細(xì)胞中發(fā)生多重遺傳突變單個癌基因激活和抑癌基因失活不足以引起腫瘤細(xì)胞的顯著擴(kuò)增，因?yàn)榧?xì)胞對凋亡的易感性也同時增加；凋亡抑制是腫瘤細(xì)胞能夠生長到足以威脅宿主所必須的；例如：Rb的失活僅會促進(jìn)p53依賴的凋亡，但不會引起腫瘤，除非細(xì)胞的凋亡過程被抑制；Apoptosisandoncogenesis67

細(xì)胞信號轉(zhuǎn)導(dǎo)調(diào)控與疾病防治Regulationofcellularsignalsinprevention&treatmentofdiseases以信號轉(zhuǎn)導(dǎo)蛋白為靶分子對疾病進(jìn)行防治STI571asaparadigm(范例）

forcancertherapyIn1960,describedthepresenceofaconsistentchromosomalabnormalityinCML（一種白血病)，so-calledPhiladelphiachromosome(Ph)Areciprocaltranslocationbetweenthelongarmsofchromosomes9and22,t(9:22)(q34;q11),Themolecularconsequenceofthiseventisthegenerationofachimericbcr-ablgene(22:9)ThetyrosinekinaseactivityofBcr-Ablstimulatesavarietyofsignalingpathways,leadingtoalterationsinsurvivalpropertiesofcells“Rational”Approach:bcr-abldirectedagentserbstatinlavendustinpiceatannolAG957AG1112CGP57148B=STI571Naturalproductempiriclead1stgen.synthetic2ndgen.synthetic;inclinicbcrSH2SH2VSH2/SH3kinaseNTDNAActinbcrAblTyrosinekinaseRaspathwayJAK-STATpathwayPI3KpathwayFAKIntegrinActinPaxillinProliferationTransformationAdhesionGlivecNEJM344:1031,2001EfficacyAndS