考研资料北京大学细胞生物学第六章基质与内膜(上)课件

Chapter6Cytoplasmicmatrix,Endomembranesystem,ProteinSortingandmembranetraffickingLearningobjective1.CompartmentalizationinEukaryoticCells;ThestructuralandfunctionalrelationshipamongtheER,Golgicomplexes,lysosomesandplasmamembranesofeukaryoticcells;Thepathwaysofproteinstargetingandsorting,anditsmechanisms;Thewaysofproteinmodificationsandintracellularsitesaftertheyaresynthesized;Typesofvesicletransportandtheirfunctions.1.TheCompartmentalizationinEukaryoticCellsMembranesdividethecytoplasmofeukaryoticcellsintodistinctcompartments.

Threecategoriesineukaryoticcells:(1)theendomembranesystem:ER,Golgicomplex,Lys.,

secretoryvesicles.(2)thecytosol.(3)mitochondria,chloroplasts,peroxisomes,andthenucleus.Membrane-boundstructures(organelles)arefoundinalleukaryoticcells.CytoplasmicmatrixanditsfunctionsCytoplasmicMatrix:Theregionoffluidcontentofthecytoplasmoutsideofthemembranousorganelles.Aqueoussolutionoflargeandsmallmoleculesincludingfilamentsofcytoskeletonwhichactasorganizerforsomeorder.TheCytosolisthesiteofproteinsynthesisanddegradationormodification.Italsoperformsmostofthecell’sintermediarymetabolism.Cytoplasmicmatrix(Cytosol)and

EndomembraneSystemB.EndomembraneSystemEndomembraneSystem:ThestructuralandfunctionalrelationshiporganellesincludingER,Golgicomplex,lysosome,endosomes,secretoryvesicles.Membrane-boundstructures(organelles)arefoundinalleukaryoticcells.Intracellularcompartment%oftotalcellvolumeCytosol54Mittchondria22RoughERcisternae9SmoothERcisternaeplusGolgicisternae6Nucleus6Peroxisome1Lysosomes1Endosomes1RelativevolumesoccupiedbythemajorintracellularcompartmentsinLiverCellD.Afewapproachestothestudyofcytomembranes

Insightsgainedfromautoradiography;Insightsgainedfromthebiochemicalanalysisofsubcellularfractions;Insightsgainedfromthestudyofgeneticmutants;Thedynamicactivitiesofendomembranesystemsarehighlyconserveddespitethestructuraldiversityofdifferentcelltypes.DeDuve,A.ClaudeandG.Palade,1974NobelPlrize2.ThestructureandfunctionsofEndoplasmicReticulum(ER)RoughendoplasmicreticulumandSmoothendoplasmicreticulum

RERhasribosomesonthecytosolicsideofcontinuous,flattenedsacs(cisternae);SERisaninterconnectingnetworkoftubularmembraneelements.A.FunctionsoftherERProteinssynthesizedonribosomesofrERinclude:

secretoryproteins,integralmembraneproteins,solubleproteinsoforganelles.

Modificationandprocessingofnewlysynthesizedproteins:

glycosylationintherER;N-linked:linkedtotheamidenitrogenofasparagine(ER)O-linked:linkedtothehydroxylgroupserineorthreonineviaGalNac(inGolgi)Theprecursorof14residuesisthesameinplants,animals,andsingle-celledeukaryotesthenremove3glucosesand1mannoseintheER

Qualitycontrolofofnewlysynthesizedproteins---TheroleofN-linkedglycosylationinERproteinfoldingQualitycontrol:ensuringthatmisfoldedproteinsdonotleaveERThelumenofrERcontains:Bipandcalnexin(chaperones):thatrecognizeandbindtounfoldedormisfoldedproteinsandgivethemcorrectconformation;Proteindisulfideisomerase(PDI);GT(glucosyl-transferase,monitoringenenzyme)recognizeunfoldedormisfoldedproteinsandaddsaglucosetotheendofoligo..Theroleofphospholipidtranslocatorsinlipidbilayersynthesisphospholipidtranslocators=Scramblase(ABCtransporterFamily)B.FunctionsofthesERSynthesisofsteroidsinendocrinecells.Detoxificationoforganiccompoundsinlivercells.Systemofoxygenases---cytochromep450familyReleaseofglucose6-phosphateinlivercells.SequestrationofCa2+.Ca2+-ATPase3.ThestructureandfunctionsofGolgicomplexA.ThepolarityofGolgicomplexB.TheFunctionsofGolgicomplexGlycosylationintheGolgicomplexGolgicomplexplaysakeyroleintheassemblyofthecarbohydratecomponentofglycoproteinsandglycolipids.ThecorecarbohydrateofN-linkedoligosaccharidesisassembledintherER.ModificationstoN-linkedoligosaccharidesarecompletedintheGolgicomplex.O-linkedoligosaccharidestakesplaceinGolgicomplex.StructureoftypicalO-andN-linkedoligosaccharidesCoreRegionAfterR.KornfeldandS.Kornfeld,1985,Annu.Rev.Biochem.

45:631TheGolginetworksareprocessingandsortingstationswhereproteinsaremodified,segregatedandthenshippedindifferentdirections.Golgicomplexandcell’ssecretionContinual,unregulateddischargeofmaterialfromthecellsThedischargeofproductsstoredincytoplasmicgranules,inresponsetoappropriatestimuli.StableexpressionofmammalianGolgiproteins.a,b,OverlaidimmunofluorescenceandphaseimagesofGRASP–YFP(a)andNAGTI–YFP(b)instable,transgeniccelllinesofToxoplasmagondii.c–h,ImmunofluorescenceimagesofatransgeniccelllineexpressingbothGRASP–CFP(green)andNAGTI–YFP(red)before(c–e)orafter(f–h)treatmentwith5mg/mlBFAfor10minat37ºC.Mergedimagesareshownontheright.AsterisksindicateasecretedformofNAGTI–YFPthataccumulatesintheparasitophorousvacuole.Scalebars,5mm.Immunoelectronmicroscop