細(xì)胞生物學(xué)網(wǎng)絡(luò)課件08年第4章a minimizer

CHAPTER4

InteractionsBetweenCellsandTheirEnvironmentOUTLINE4.1CELLSURFACE4.2CELLENVIRONMENT4.3CELLRECOGNIZATION4.4CELLJUNCTION

4.1CellSurface◆在結(jié)構(gòu)上，包括：●細(xì)胞被(cellcoat)●細(xì)胞質(zhì)膜●表層胞質(zhì)溶膠(corticolcytosol)◆在功能上：●保護(hù)細(xì)胞,使細(xì)胞有一個相對穩(wěn)定的內(nèi)環(huán)境；●參與細(xì)胞內(nèi)外的物質(zhì)交換和能量交換；●參與信號的識別和信息的傳遞；●參與細(xì)胞運動；●維護(hù)細(xì)胞的各種形態(tài)；●與免疫、癌變等有十分密切關(guān)系。表層胞質(zhì)溶膠(cytosol)：

其中含有高濃度的蛋白質(zhì),其厚度在哺乳類細(xì)胞為0.1-0.2μm,其中沒有核糖體和線粒體,但是有較多的微絲和微管,它們對于維持細(xì)胞的形態(tài)和運動具有重要作用。細(xì)胞被◆Glycocalyx)●組成：

由細(xì)胞表面的碳水化合物形成的質(zhì)膜保護(hù)層，又稱為多糖包被。●功能：Theglycocalyxisthoughttomediatecell-cellandcell-substratuminteractions,providemechanicalprotectiontocells,andserveasabarriertoparticlesmovingtowardtheplasmamembrane.4.1.2PLANTCELLWALLS

植物細(xì)胞壁的作用◆提供機(jī)械強(qiáng)度◆保護(hù)細(xì)胞免遭滲透及機(jī)械損傷◆植物細(xì)胞壁是一個動態(tài)結(jié)構(gòu)，能夠進(jìn)行很多活動:●與細(xì)胞壁有關(guān)的酶能夠吸收細(xì)胞外的營養(yǎng)，生成能夠通過細(xì)胞膜進(jìn)入細(xì)胞的小分子化合物?！窦?xì)胞壁也可以作為物質(zhì)通透的障礙，在代謝和分泌過程中起重要作用。細(xì)胞壁的結(jié)構(gòu)組成◆植物的細(xì)胞壁相當(dāng)于動物細(xì)胞的細(xì)胞

外基質(zhì)(!!!)：●動物細(xì)胞的細(xì)胞外基質(zhì)的主要成分是蛋白質(zhì)分子；●植物的細(xì)胞壁主要是多糖，其中最主要的是纖維素?！糁参锛?xì)胞壁的骨架：纖維素◆植物細(xì)胞壁的骨架：纖維素●Cellulosemoleculesareorganizedintomicrofibrilsthatconferrigiditytothecellwallandprovideresistancetotensile(pulling)forces.

?●Eachmicrofibrilis5-10nmindiameterandiscomposedofbundlesof30to60cellulosemoleculesorientedparalleltooneanotherandheldtogetherbyhydrogenbonds.?◆Thematrixoftheplantcellwalls■Hemicellulose

●Hemicellulosesarebranchedpolysaccharideswhosebackboneconsistsofonesugar,suchasglucose,andsidechainsofothersugars,suchasxylose.

●Hemicellulosemoleculesbindtothesurfacesofcellulosemicrofibrils,cross-linkingthemintoacomplexstructuralnetwork.■Pectins：

●Pectinsareaheterogeneousclassofnegativelychargedpolysaccharidescontaininggalacturonicacid（半乳糖醛酸）；●Liketheglycosaminoglycansofanimalcellmatrices,pectinsholdwaterandthusformanextensivehydratedgel（水合膠）thatfillsinthespacesbetweenthefibrouselements；●Whenaplantisattackedbypathogens,fragmentsofpectinsreleasedfromthewalltriggeradefensiveresponsebytheplantcell；●Purifiedpectinisusedcommerciallytoprovidethegel-likeconsistencyofjamsandjellies.■StructureProteins:

StructureProteinfunctionsarenotwellunderstood.Oneclass,theextensins,providestructuralsupportandmayformabarriertoinvadingmicroorganisms.植物細(xì)胞壁的分泌合成◆中間層形成：

主要是果膠。果膠是相鄰兩細(xì)胞壁所共有，并且具有將兩個細(xì)胞連接在一起的作用?！舫跎谛纬桑菏羌?xì)胞正在生長時形成的。初生壁的厚度為100-200nm,與動物細(xì)胞的基膜相當(dāng)。初生壁由纖維素、半纖維素、果膠和糖蛋白等松散組成?！舸紊谛纬桑?/p>

是在細(xì)胞停止生長后分泌形成的。主要是增加細(xì)胞壁的厚度和強(qiáng)度。次生壁主要在初生壁的內(nèi)層。144.2Extracellularmatrix◆Manytypesofanimalcellsaresurroundedbyanextracellularmatrix(ECM)--anorganizednetworkofextracellularmaterialsthatispresentbeyondtheimmediatevicinityoftheplasmamembrane.◆TheECMismorethananinertpackingmaterial,itoftenplaysakeyregulatoryroleindeterminingtheshapeandactivitiesofthecell.◆能夠分泌和形成細(xì)胞外基質(zhì)的主要細(xì)胞類群是成纖維細(xì)胞(fibroblast)和其他特化組織的細(xì)胞。15

Forexample:●EnzymaticdigestionoftheECMthatsurroundsculturedcartilage(軟骨）cellsormammaryglandepithelialcellscausesamarkeddecreaseinthesyntheticandsecretoryactivitiesofthecells.●Additionofextracellularmatrixmaterialsbacktotheculturedishrestoresthedifferentiatedstateofthecellsandtheirabilitytoproducetheirusualcellproducts.

16◆細(xì)胞外基質(zhì)的組成可分為三大類∶●蛋白聚糖(proteoglycan)●結(jié)構(gòu)蛋白如膠原和彈性蛋白，它們賦予基質(zhì)一定的強(qiáng)度和韌性。●黏著蛋白(adhesiveproteins)如纖連蛋白和層粘蛋白，它們促使細(xì)胞同基質(zhì)結(jié)合。174.2.1細(xì)胞外基質(zhì)的基礎(chǔ)物質(zhì)蛋白聚糖(Proteoglycan,PG)◆結(jié)構(gòu)與功能

●Protein-polysaccharidecomplexiscalledaproteoglycan

●Aproteoglycanconsistsofacoreproteinmoleculetowhichchainsofglycosaminoglycans(GAGs,糖胺聚糖)arecovalentlyattached.●BecauseofthenegativechargesborneonthesulfatedGAGs,proteoglycansbindhugenumbersofcations,whichinturnbindlargenumbersofwatermolecules.Asaresult,proteoglycansformaporous,hydratedgelthatfillstheextracellularspacelikepackingmaterialandresistscrushing(compression)forces.

18◆Glycosaminoglycans

●Eachglycosaminoglycanchainiscomposedofarepeatingdisaccharide;thatis,ithasthestructure-A-B-A-B-A-,whereAandBrepresenttwodifferentsugars.●GAGsarehighlyacidicduetothepresenceofbothsulfateandcarboxylgroupsattachedtothesugarrings.

●糖胺聚糖的二糖單位之一是氨基己糖(氨基葡萄糖或氨基半乳糖),故稱為糖胺聚糖?！裉前肪厶前ā昧蛩彳浌撬?chondroitinsulfate)透明質(zhì)酸(hyaluronicacid)等。19構(gòu)成糖胺聚糖的二糖20◆透明質(zhì)酸(hyaluronicacid)

細(xì)胞外基質(zhì)中發(fā)現(xiàn)的大多數(shù)糖胺聚糖都是作為蛋白聚糖的一個成分而存在，惟一例外的是透明質(zhì)酸，它在細(xì)胞外

基質(zhì)中也可游離存在。

透明質(zhì)酸在結(jié)締組織中起強(qiáng)化、彈性和潤滑作用,具有抗壓能力。21

4.2.2結(jié)構(gòu)蛋白膠原(Collagen)◆基本特性：●Collagenisafamilyoffibrousglycoproteinsthatarepresentonlyinextracellularmatrices.●Collagenisthesinglemostabundantproteininthehumanbody(constitutingmorethan25percentofallprotein),●Collagensarefoundthroughouttheanimalkingdomandarenotedfortheirhightensilestrength,thatis,theirresistancetopullingforces.Itisestimatedthatacollagenfiber1mmindiameteriscapableofsuspendingaweightof10kgwithoutbreaking.●Collagenisproducedprimarilybyfibroblasts,thecellsfoundinvarioustypesofconnectivetissues,andalsobysmoothmusclecellsandepithelialcells.

22◆膠原的類型●Nineteendistincttypesofcollagenhavebeenidentified.

●Eachcollagentypeisrestrictedtoparticularlocationswithinthebody,buttwoormoredifferenttypesareoftenpresenttogetherinthesameECM.23◆Structuralfeatures

●Allcollagenmoleculesaretrimersconsistingofthreepolypeptidechains,calledchains.●Alongatleastpartoftheirlength,thethreepolypeptidechainsofacollagenmoleculearewoundaroundeachothertoformaunique,rod-liketriplehelix24●在膠原纖維內(nèi)部,有分子內(nèi)和分子間的交聯(lián)。分子內(nèi)交聯(lián)是指原膠原的三條鏈之間的賴氨酸殘基間的交聯(lián),分子間的交聯(lián)是指不同原膠原間的賴氨酸交聯(lián)。

這種分子間的交聯(lián),使得在膠原纖維內(nèi)部形成膠原蛋白分子呈1/4平行交替排列,即一個原膠原的頭部與下一個原膠原的尾部有一個小的間隙分隔。25◆膠原的合成、裝配與運輸●哺乳動物具有大約20種不同的膠原基因，編碼各種不同組織所需要的膠原。●首先是在粗面內(nèi)質(zhì)網(wǎng)上合成帶有信號肽的前原膠原(preprocollagan)?！衲z原纖維的加工組裝始于內(nèi)質(zhì)網(wǎng)、在高爾基體中繼續(xù)進(jìn)行,最后完成于細(xì)胞外。26◆膠原的作用

◆膠原是骨、腱和皮膚組織中的主要蛋白，在這些組織的細(xì)胞外基質(zhì)中,膠原起著細(xì)胞外基質(zhì)骨架作用;

◆膠原具有促進(jìn)細(xì)胞生長的作用;

◆在細(xì)胞分化中，膠原基質(zhì)和提純的膠原底物具有維持并誘導(dǎo)細(xì)胞分化的作用。27

膠原酶遺傳缺陷

某些人具有膠原酶的遺傳缺陷，這樣,他們的膠原纖維就不能正確地裝配，其結(jié)果，皮膚和各種其它的結(jié)綈組織就會降低它們的強(qiáng)度變得非常的松弛。28彈性蛋白(Elastin)◆是彈性纖維(elasticfibers)的主要成分。◆功能：能夠賦予細(xì)胞外基質(zhì)彈性。◆彈性蛋白也是富含甘氨酸和脯氨酸的蛋白質(zhì)。與同膠原不同的是，彈性蛋白的脯氨酸沒有羥基化，所以沒有羥脯氨酸的存在。294.2.3黏著蛋白

黏著蛋白(adhesiveprotein)是細(xì)胞外基中質(zhì)的第三類成分，之所以將這些蛋白稱為黏著蛋白，主要是這些些蛋白起著將細(xì)胞外基質(zhì)與細(xì)胞聯(lián)系起來的橋梁作用。30纖粘連蛋白(Fibronectin,FN)◆存在：●Fibronectinareafamilyofcloselyrelatedadhesiveglycoproteinsthatwidelydistributedthroughouttheanimalkingdom;●Fibronectinoccursinasolubleforminthebloodandotherbodyfluids；●Asinsolublefibrilsintheextracellularmatrix。31◆結(jié)構(gòu)特點：■Fibronectinpolypeptideisconstructedfromasequenceofapproximately30independentlyfoldingFndomains■Eachofthetwopolypeptidechainsthatmakeupafibronectinmoleculecontains：●BindingsitesforothercomponentsoftheECM,suchascollagensandproteoglycans.Thesebindingsitesfacilitateinteractionsthatlinkthesediversemoleculesintoastable,interconnectednetwork.●Bindingsitesforreceptorsonthecellsurface，thesebindingsitesholdthecellinastableattachmenttotheECM.32◆RGD序列●用蛋白酶消化纖粘連蛋白與細(xì)胞結(jié)合區(qū),發(fā)現(xiàn)這一結(jié)構(gòu)域中Arg-Gly-Asp三肽序列負(fù)責(zé)同細(xì)胞表面的結(jié)合,●Arg-Gly-Asp序列(又稱RGD序列)同樣存在于細(xì)胞外基質(zhì)和血液的其它類型的黏著蛋白序列中。33◆功能：◆FN最主要的功能是介導(dǎo)細(xì)胞的黏著?！粲捎贔N具有同時與細(xì)胞外基質(zhì)各類成分相結(jié)合的特點,并可促進(jìn)細(xì)胞外基質(zhì)的其它成分的沉積,故認(rèn)為FN是細(xì)胞外基質(zhì)的組織者。34層粘連蛋白(laminin,LN)◆Lamininsareafamilyofextracellularglycoproteinsthatconsistofthreedifferentpolypeptidechainslinkedbydisulfidebondsandorganizedintoamoleculeresemblingacrosswiththreeshortarmsandonelongarm？◆層粘連蛋白主要存在于基膜(basallamina)結(jié)構(gòu)中，是基膜的主要結(jié)構(gòu)成分。35◆層粘連蛋白的功能■首先作為基膜的主要結(jié)構(gòu)成分對基膜的組裝起關(guān)鍵作用。它可作為黏著因子介導(dǎo)細(xì)胞黏著于膠原,使之發(fā)生鋪展?！鯡xtracellularlamininscangreatlyinfluenceacell'spotentialformigration,growth,anddifferentiation.

364.2.4細(xì)胞外基質(zhì)與細(xì)胞的相互作用基膜(Basementmembrane)◆Basementmembrane(orbasallamina)isacontinuoussheet50to200nmthick:■Surroundsmuscleandfatcells;■Underliesthebasalsurfaceofepithelialtissues,suchastheepidermisoftheskin,ortheliningofthedigestiveandrespiratorytracts,■Underliestheinnerendothelialliningofbloodvessels.37◆基膜的組成■層粘連蛋白是基膜的主要成分，也是基膜的組織者；■巢蛋白(entactin)■Ⅳ型膠原■硫酸肝素糖蛋白。

Ⅳ型膠原是基膜的核心分子，排列成網(wǎng)狀；層粘連蛋白同Ⅳ型膠原結(jié)合，覆蓋在細(xì)胞表層。38◆基膜的功能●Basementmembranesprovidemechanicalsupportfortheattachedcells;●Serveasasubstratumforcellmigration;●Separateadjacenttissueswithinanorgan;●Basementmembranesalsoserveasabarriertotheinvasionoftissuesbyerrantcancercells.39Matrixmetalloproteinases(MMPs)◆ThedegradationofECMmaterialsisplishedlargelybyafamilyofzinc-containingenzymescalledmatrixmetallopro-teinasesthatareeithersecretedintotheextra-cellularspaceorboundtotheexternalsurfaceoftheplasmamembrane.◆TheexcessiveorinappropriateactivityofMMPsislikelytocausedisease.Infact,MMPshavebeenimplicatedinanumberofpathologicalconditions,includingarthritis,multiplesclerosis,atherosclerosis,toothdecay,andtumorprogression.40整聯(lián)蛋白(integrin)◆Integrinsareafamilyofintegralmembraneproteinsthoughttobepresentonthesurfacesofvirtuallyalltypesofvertebratecells.41◆整聯(lián)蛋白結(jié)構(gòu):●Integrinsarecomposedoftwomembrane-spanningpolypeptidechains,anchainandachain,thatarenoncovalentlylinked.

●Twosubunitsarearrangedsoastoformaglobularextracellularheadconnectedtothemembranebyapairofrigidstalks.●Bothsubunitshaveasingletransmembranehelixandasmallcytoplasmicdomain.●N-terminalextracellularportionofthesubunitconsistedofsevenrepeatingmodules,eachcomprisedofapproximately