1、Chapter 13Cell apoptosis 1.Extracellular cotrol of cell division,cell growth,and apoptosisMitogens stimulate G1-Cdk and G1/S-Cdk activitiesPRIZED Horvitz,and Sulston share Physiology or Medicine Nobel（2002）“for their discoveries concerning genetic regulation for their discoveries concerning genetic
2、regulation of organ development and programmed cell death”of organ development and programmed cell death”1090 131=959(cells)机体结构机体结构细胞增殖细胞增殖细胞分化细胞分化细胞凋亡细胞凋亡细胞信号转导细胞信号转导染色体染色体（DNADNA与蛋白质的相互作用）与蛋白质的相互作用）衰老衰老A simplified model of one way that mitogens stimulate cell divisionHuman cells have a built-in
3、limitation on the number of times they can divideThe cell division is cotrolled not only by extracellular mitogens but also by intracellular mechanisms that can limit cell proliferation.Cell-cycle arrest or apoptosis induced by excessive stimulation of mitogenic pathways.Extracellular growth factors
4、 stimulate cell growthActivation of cell-surface receptors Activation of PI 3-kinaseActivation of elF4E(translation initiation factor)and S6 kinase(phosphorylates ribosomal protein S6)Increasing protein synthesis and cell growth2.Apoptosis,Programmed cell death Biological functions of apoptosis In d
5、evelopment,homeostasis,tumor surveillance,and the function of the immune system.细胞凋亡是多细胞生物在发育过程中，一种由基因控制的主动的细胞生理性自杀行为。Morphological and biochemical characteristics of apoptosis Morphologi changes:Early:Chromosome condensation,cell body shrink Later:Blebbing and Nucleus and cytoplasm fragment Apoptot
6、ic bodies At last:PhagocytosedA、Normal cell B、Apoptosis:Apoptotic bodies Biochemical characteristics of apoptosis:Apoptosis induced by Cyto CLane 10 h 21 h 32 h 43 h 54 h 6Control 7Marker 2.0kbp1.00.50.2180200bp DNA ladder,Accumulation of tTG,PS flip-flopContrast ofApoptosis and necrosisApoptosisNec
7、rosisDeath by apoptosis is a neat,orderly process3.Molecular mechanisms of apoptosisEarly researches(MIT:Robert Horrid,1986)C.elegans:1090 cells,The Finding of CED3 mutantWithout losing any of theircells to apoptosis.CED3 gene play a crucial role in the process of apoptosis.C elegans:a millimeter lo
8、ng,transparent body only a few cell types,from zygote to mature adult only in 3.5days.131 cells death.线虫体细胞凋亡研究：线虫体细胞凋亡研究：PCD相关基因相关基因15个，分为四组：个，分为四组：1、与PCD有关的基因，负责PCD控制：ced-3、ced-4和ced-9。2、与PCD过程吞噬作用有关：ced-1、ced-2、ced-5-8 和 ced-10。3、核酸酶基因（nuc-1）,控制DNA降解，但非PCD所必须。4、影响特异细胞类型PCD的基因：ces-1、ces-2、cgl-1、和
9、her-1.保守性高，在哺乳动物中有相应同源物：Ced-3=ICE,Ced-4=Apaf-1,Ced-9=Bcl-2.Mammalian:CED3 is related to mammalian interleukin-1converting enzyme(ICE or caspase-1)Apoptosis is carried out by a proteolytic system caspase(1)Why called caspase?Active site:CysteineCleavage site:Asparatic acid Cysteine Asparatic acid spe
10、cific proteaseAps-Xxx天冬氨酸特异性的半光氨酸蛋白水解酶Apoptosis can be divided into two phases：Activation phase：The cell responds to“death signals”that commit it to undergoing self-destruction.Execution phase：The death sentence is carried out.Apoptosis cells are recognized by phagocytes because they carry exposed m
11、arkers,called“eat me”signals.The best studied“eat me”signal is the presence of phosphatidylserine molecules in the outer leaflet of PM of apoptotic cells(by flop-flipase).How to activate caspases?All caspases expressed as proenzymes ProcaspasesProcaspaseNH2-terminal prodomain:Highly variableLarge su
12、bunit(20kD)Small subunit(10kD)How are procaspases activated to initiate the caspase cascade?The activation is triggered by adaptor proteins that bring multiple copies of specific procaspases.3 groups of caspase:1、apoptotic initiators:caspase-2,caspase-8,caspase-9 and caspase-10 2、apoptotic execution
13、ers:caspase-3,caspase-6，caspase-7 and 14(morphology change)3、inflammatory mediateors:caspase-1,and caspase-11 Procaspases are activated by binding to adaptor proteinsThe caspase cascade involved in apoptosisA.Procaspase activation by proteolytic cleavage.B.Caspase cascadeThe target proteins of caspa
14、se are the following:More than a dozen protein kinase,including FAK,PKC,and Raf1.FAK disrupt cell adhesion for the apoptotic cell.Lamins.Cleavage of lamins leads to the disassembly of the nuclear lamina and shrinkage of the nucleus.Proteins required for cell structure.Such as IF,actin,and gelsilin.C
15、leavage and inactivation of these proteins lead to changes in cell shape.Induce cell display signals marked it for phagocytosis.The inhibitor of CAD(Caspase-activated Dnase,an endonuclease).Cleavage of CAD inhibitor lead to activation of CAD,once activated,CAD translocates from the cytosol to the nu
16、cleus severing DNA into fragments.Enzymes involved in DNA repair.Which are inactivated by caspase cleavage.DNA repair is a homeostatic activity that is inappropriate in an apoptotic cell.Molecular pathways of apoptosisTwo principle pathways Extrinsic pathwayIntrinsic pathway(1)Extrinsic pathway:Fas
17、Signaling PathwayFas(also called Apo-1 or CD95)is a member of the tumor necrosis factor receptor(TNFR)superfamily.Receptor-mediated pathway of apoptosisBcl-2 Family(cytoplasmic factors):Bad,Bid,and bax:promote apoptosis;Bcl-X,Bcl-w,and Bcl-2:prevent apoptosis.Internal stimuli:DNA damage,high Ca2+,Ox
18、idative stress(2)Intrinsic pathway:Mitochondrial pathwayThe mitochondria-mediated pathway of apoptosisVarious types ofcellular stressBcl-2 family:Bad or Bax to become inserted into OM of MitRelease of cytochrome c from I-O space of Mit.Form a multisubunit complex;and Caspase Cascade,Activation of caspase-2 is required for permeabilization of mitochondria,release of cytochrome c,and apoptosisPathways to cell death in C.elegans and mammals
