Apoptosis initiated by Bcl-2-regulated caspase activation independently of the cytochrome c/Apaf-1/caspase-9 apoptosome

Apoptosis is an evolutionarily conserved cell suicide process executed by cysteine proteases (caspases) and regulated by the opposing factions of the Bcl-2 protein family. Mammalian caspase-9 and its activator Apaf-1 were thought to be essential, because mice lacking either of them display neuronal hyperplasia and their lymphocytes and fibroblasts seem resistant to certain apoptotic stimuli. Because Apaf-1 requires cytochrome c to activate caspase-9, and Bcl-2 prevents mitochondrial cytochrome c release, Bcl-2 is widely believed to inhibit apoptosis by safeguarding mitochondrial membrane integrity. Our results suggest a different, broader role, because Bcl-2 overexpression increased lymphocyte numbers in mice and inhibited many apoptotic stimuli, but the absence of Apaf-1 or caspase-9 did not. Caspase activity was still discernible in cells lacking Apaf-1 or caspase-9, and a potent caspase antagonist both inhibited apoptosis and retarded cytochrome c release. We conclude that Bcl-2 regulates a caspase activation programme independently of the cytochrome c/Apaf-1/caspase-9 'apoptosome', which seems to amplify rather than initiate the caspase cascade.     

Bcl-2 family proteins regulate the release of apoptogenic cytochrome c by the mitochondrial channel VDAC.

During transduction of an apoptotic (death) signal into the cell, there is an alteration in the permeability of the membranes of the cell's mitochondria, which causes the translocation of the apoptogenic protein cytochrome c into the cytoplasm, which in turn activates death-driving proteolytic proteins known as caspases. The Bcl-2 family of proteins, whose members may be anti-apoptotic or pro-apoptotic, regulates cell death by controlling this mitochondrial membrane permeability during apoptosis, but how that is achieved is unclear. Here we create liposomes that carry the mitochondrial porin channel (also called the voltage-dependent anion channel, or VDAC) to show that the recombinant pro-apoptotic proteins Bax and Bak accelerate the opening of VDAC, whereas the anti-apoptotic protein Bcl-x(L) closes VDAC by binding to it directly. Bax and Bak allow cytochrome c to pass through VDAC out of liposomes, but passage is prevented by Bcl-x(L). In agreement with this, VDAC1-deficient mitochondria from a mutant yeast did not exhibit a Bax/Bak-induced loss in membrane potential and cytochrome c release, both of which were inhibited by Bcl-x(L). Our results indicate that the Bcl-2 family of proteins bind to the VDAC in order to regulate the mitochondrial membrane potential and the release of cytochrome c during apoptosis.     

Role of Bax and Bak in mitochondrial morphogenesis

Bcl-2 family proteins are potent regulators of programmed cell death. Although their intracellular localization to mitochondria and the endoplasmic reticulum has focused research on these organelles, how they function remains unknown. Two members of the Bcl-2 family, Bax and Bak, change intracellular location early in the promotion of apoptosis to concentrate in focal clusters at sites of mitochondrial division. Here we report that in healthy cells Bax or Bak is required for normal fusion of mitochondria into elongated tubules. Bax seems to induce mitochondrial fusion by activating assembly of the large GTPase Mfn2 and changing its submitochondrial distribution and membrane mobility-properties that correlate with different GTP-bound states of Mfn2. Our results show that Bax and Bak regulate mitochondrial dynamics in healthy cells and indicate that Bcl-2 family members may also regulate apoptosis through organelle morphogenesis machineries.     

线粒体外膜通道蛋白VDAC与靶向肿瘤细胞凋亡

VDAC(Voltage-dependent anion channel)是位于线粒体外膜上的一种主要通道蛋白,参与线粒体内外物质和能量的运输,在线粒体与细胞其它部位的通讯中起重要调节作用.近年来研究发现,VDAC也是线粒体与其它蛋白质相互作用的功能结合位点,可与多种凋亡调节蛋白(如HK-Ⅰ/Ⅱ、Bcl-2家族蛋白、tubulin、MAP2/4等)以及非蛋白调节因子相互作用,参与调控细胞凋亡.因此,VDAC成为线粒体凋亡通路中一种关键的靶蛋白.本文对近年来VDAC在肿瘤细胞凋亡中的作用机制进行简要综述.     

Bcl-2蛋白质家族调控细胞凋亡机制的研究进展

细胞凋亡是一种受基因调控的响应凋亡刺激的细胞程序性死亡方式.通过线粒体途径引发的凋亡主要由Bcl-2(B-cell lymphoma 2)蛋白质家族成员之间复杂的相互作用进行调控,然而科学界对其具体的相互作用模式一直存在争议.首先综述了近年来Bcl-2蛋白质家族成员之间相互作用的生物学机制,然后总结了细胞凋亡具有双稳性和该家族成员相互作用模式的数学模型,最后通过对目前流行的3种作用模式(即直接激活模式、间接激活模式、统一模式)进行数值模拟和分岔分析,认为统一模式是更合理的作用模式.以期能更好地理解病理细胞中可能存在的作用机制,从而为因凋亡异常引起的癌症、阿尔兹海默症等疾病的治疗和控制提供思路.     

PPARγ激动剂诱导HT-29凋亡及周期阻滞的作用

PPAR属于核受体超家族,与特异配体结合后调控一些基因的表达,这些受调控的基因涉及脂质的代谢,糖尿病以及肿瘤等多个方面.目的是研究PPAR γ激动剂罗格列酮诱导结肠癌细胞HT-29凋亡及细胞周期阻滞的作用,并对其机制做相应的探讨.试验结果显示,罗格列酮可诱导HT-29细胞发生凋亡,并阻滞细胞于G1期,此效果伴随着Bcl-2的表达降低,p21的表达升高.罗格列酮在升高PPAR γ表达的同时,也激活了细胞内ERK的传导通路.因此,罗格列酮是通过诱导结肠癌细胞凋亡及周期阻滞而发挥其抗肿瘤作用,此作用为PPAR γ依赖的,并且与激活ERK通路有关.这些研究结果提示PPAR γ有望成为结肠癌治疗的分子靶点.     

As4S4诱导宫颈癌Hela细胞凋亡及相关分子机制研究

研究AS4S4对宫颈癌Hela细胞生长抑制厦诱导凋亡作用，并探讨可能的分子机制。以不同浓度的AS4S4分不同时间段处理Hela细胞，用四甲基偶氮唑蓝（MTT）法测定细胞增殖抑制率；采用流式细胞术测定细胞凋亡；Western blotting测凋亡相关蛋白Bcl-2，Caspase3表达的变化。结果表明，经AS4S4处理的Hela细胞，增殖受到抑制，作用呈明显的时效和量效关系，细胞凋亡率明显增高并呈浓度依赖性；Western blotting示Bcl-2表达下降，Caspase3表达增加。因此，AS4S4对Hela细胞具有增殖抑制和诱导凋亡作用，其机制与下调Bcl-2蛋白、上调Caspase3蛋白表达有关。     

Bcl-2 maintains B cell memory

The number of lymphocytes in an animal is remarkably constant despite antigen-driven proliferation and a high rate of B-cell lymphopoiesis. This reflects the relatively brief lifespan of many newly generated B cells and argues for a well-regulated death mechanism. Even so, a secondary immune response can be generated years after a primary exposure to antigen. Antigen that might restimulate B cells persists for extended periods on follicular dendritic cells in the light zone of germinal centres. Antigen-binding B cells have also been found months after the end of obvious cell division. The precise signal that enables certain B cells to emerge as long-term surviving memory cells is unknown. Bcl-2, an inner mitochondrial membrane protein, blocks programmed cell death in B cells. We report here that this proto-oncogene maintains immune responsiveness. Transgenic mice overproducing Bcl-2 have a long-term persistence of immunoglobulin-secreting cells and an extended lifetime for memory B cells.     

线粒体腺苷酸转运体在宫颈癌组织中的表达变化及其与细胞凋亡的关系

 为探讨线粒体腺苷酸转运体（ANT）在宫颈癌组织中的表达变化及其与细胞凋亡的关系,收集维吾尔族妇女浸润性宫颈鳞癌患者的组织36 例,正常或者慢性宫颈炎宫颈组织32 例作为对照。分别运用荧光定量PCR（Q-PCR）、蛋白免疫印迹（westernblot,WB）技术,检测线粒体腺苷酸转运体ANT1、ANT2、ANT3,以及Bax、Bcl-2、p53 在不同宫颈组织中的mRNA 和蛋白表达水平及其差异。运用TUNEL 法测定不同宫颈组织中的细胞凋亡程度。Q-PCR 和WB 结果显示,与正常对照组相比,p53、Bax 在宫颈癌患者宫颈组织中表达降低,而Bcl-2 和ANT3 表达升高,差异有统计学意义（P<0.05）。TUNEL 结果显示,宫颈癌组的凋亡指数（AI）明显高于正常对照宫颈炎组,两组之间差异有统计学意义（P<0.05）。线粒体腺苷酸转运体ANT 在宫颈癌组织中的异常表达导致线粒体功能紊乱,从而干扰细胞凋亡过程,这可能是宫颈癌发生与发展的一个重要机制。     

人参水溶性总蛋白对小鼠黑色素瘤细胞B16的增殖抑制的研究及对Bcl-2/Bax表达的影响

摘 要 目的：研究人参水溶性总蛋白对小鼠黑色素瘤细胞的增殖抑制作用及对Bcl-2/Bax表达的的影响。方法：1.MTT法测定人参水溶性总蛋白对黑色素瘤B16细胞株的增殖抑制率。2. RT-PCR（Real-time PCR）法检测Bcl-2、Bax基因的mRNA表达情况。3.Western blot测定凋亡蛋白Bcl-2和Bax的表达。结果：1.人参水溶性总蛋白对小鼠黑色素瘤B16细胞株有明显的增殖抑制作用,其抑制率随着加药浓度的增加而升高,并与加药浓度呈现一定的量效关系。2.随着人参水溶性总蛋白浓度的增高（0,100,500,1000ug/mL）,RT-PCR检测的Bcl-2 mRNA相对表达量逐渐降低,Bax mRNA相对表达量逐渐升高,当加药浓度为1000ug/ml时,Bcl-2的相对表达量最低,为0.20±0.05,Bax的相对表达量最高,为16.83±0.07;与对照组相比,Bcl-2和Bax基因的相对表达量差异均有统计学意义（P＜0.05）。3.经Western blot测定,各组Bcl-2蛋白的表达均低于对照组,各组Bax蛋白表达均高于对照组,且随着加药浓度的增加,Bcl-2蛋白表达量逐渐降低,Bax蛋白表达量逐渐升高。结论：人参水溶性总蛋白可以抑制小鼠黑色素瘤B16细胞株增殖,其分子机制可能与调控Bcl-2/Bax凋亡蛋白的表达有关。     

积雪草苷调控miR-342-5p/AQP3轴保护IL-1β诱导的软骨细胞损伤

目的 探讨积雪草昔(Ass)对白细胞介素1B(IL-1B)诱导的软骨细胞损伤的影响及作用机制。方法 不同 浓度的Ass作用IL-1B诱导软骨细胞24 h,流式细胞仪检测细胞凋亡,酶联免疫吸附法检测细胞培养上清液中白细 胞介素-6(IL-6)和肿瘤坏死因子-α(TNF-α)水平,实时荧光定量PCR检测细胞中miR-342-5p和水通道蛋白3 (AQP3)mRNA表达水平,Western Blot法检测B淋巴细胞瘤-2 (Bcl-2)、B淋巴细胞瘤-2相关蛋白(Bax)和AQP3蛋 白表达水平。双荧光素酶报告基因实验验证miR-342-5p与AQP3靶向关系。转染miR-342-5p抑制剂或AQP3过表达载体至软骨细胞,上述相同方法检测抑制miR-342-5p表达或AQP3过表达对IL-1β诱导的软骨细胞凋亡及IL- 6和TNF-α表达的影响。结果 Ass可抑制IL-1β诱导的软骨细胞凋亡率、Bax蛋白、IL-6和TNF-α表达及miR- 342-5p表达(P <0. 05),促进Bcl-2蛋白、AQP3 mRNA和蛋白表达(P <0.05)。miR-342-5p在软骨细胞中负调控 AQP3表达。抑制miR-342-5p或AQP3过表达后,IL-1&诱导的软骨细胞凋亡率、Bax蛋白、IL-6和TNF-α表达降低 (P <0. 05) ,Bcl-2蛋白表达升高(P <0.05)。抑制AQP3表达逆转了抑制miR-342-5p对IL-1β诱导的软骨细胞凋 亡、Bax和Bcl-2蛋白及IL-6和TNF-α表达的影响。结论 Ass可抑制IL-1β诱导软骨细胞凋亡和炎症反应,其可 能通过调控miR-342-5p/AQP3保护软骨细胞损伤。     

BH3-only Bcl-2 family member Bim is required for apoptosis of autoreactive thymocytes

During lymphocyte development, the assembly of genes coding for antigen receptors occurs by the combinatorial linking of gene segments. The stochastic nature of this process gives rise to lymphocytes that can recognize self-antigens, thereby having the potential to induce autoimmune disease. Such autoreactive lymphocytes can be silenced by developmental arrest or unresponsiveness (anergy), or can be deleted from the repertoire by cell death. In the thymus, developing T lymphocytes (thymocytes) bearing a T-cell receptor (TCR)-CD3 complex that engages self-antigens are induced to undergo programmed cell death (apoptosis), but the mechanisms ensuring this 'negative selection' are unclear. We now report that thymocytes lacking the pro-apoptotic Bcl-2 family member Bim (also known as Bcl2l11) are refractory to apoptosis induced by TCR-CD3 stimulation. Moreover, in transgenic mice expressing autoreactive TCRs that provoke widespread deletion, Bim deficiency severely impaired thymocyte killing. TCR ligation upregulated Bim expression and promoted interaction of Bim with Bcl-XL, inhibiting its survival function. These findings identify Bim as an essential initiator of apoptosis in thymocyte-negative selection.     

去除血清诱发细胞凋亡和Bcl—2蛋白的裂解

以过表达原癌基因Bcl-2的HL－60细胞为材料,通过去除血清而诱发凋亡,应用Western blot方法检测细胞凋亡过程中Bcl-2裂解为分子量大约为20kDa的片段,进一步检测Bcl-2的结构变化,结果显示Bcl-2蛋白裂解发生在N端,裂解产物丢失了BH4结构域。通过加入凋亡相关蛋白酶caspase-3抑制剂,可抑制20kDa片段的产生,表明凋亡过程中caspase-3的激活,但细胞生长率测定表明,caspase-3抑制剂并不能阻止去血清诱发的细胞死亡。     

内耳免疫反应诱导Bcl-2和Bax表达研究

探讨内耳免疫反应过程是否引起细胞凋亡以及Bcl-2和Bax的表达情况。选用雌性白色豚鼠16只，随机分为实验组和对照组各8只，以钥孔虫戚血蓝蛋白（KLH）全身免疫后，实验组以相同抗原进行内耳免疫，对照组内耳注射等量的磷酸盐缓冲生理盐水（PBS），在内耳免疫5d后处死动物，取内耳免疫侧耳蜗制作石蜡切片。通过免疫组化检测内耳Bcl-2和Bax的表达。结果表明，内耳免疫反应可以诱导细胞凋亡的发生以及Bcl-2和Bax蛋白在其中起了重要的调节作用。     

Bcl-2 is an inner mitochondrial membrane protein that blocks programmed cell death

The t(14; 18) chromosomal translocation of human follicular B-cell lymphoma juxtaposes the bcl-2 gene with the immunoglobulin heavy chain locus. The bcl-2 immunoglobulin fusion gene is markedly deregulated resulting in inappropriately elevated levels of bcl-2 RNA and protein. Transgenic mice bearing a bcl-2 immunoglobulin minigene demonstrate a polyclonal expansion of resting yet responsive IgM-IgD B cells which display prolonged cell survival but no increase in cell cycling. Moreover, deregulated bcl-2 extends the survival of certain haematopoietic cell lines following growth-factor deprivation. By using immunolocalization studies we now demonstrate that Bcl-2 is an integral inner mitochondrial membrane protein of relative molecular mass 25,000 (25k). Overexpression of Bcl-2 blocks the apoptotic death of a pro-B-lymphocyte cell line. Thus, Bcl-2 is unique among proto-oncogenes, being localized to mitochondria and interfering with programmed cell death independent of promoting cell division.     

铅对小鼠睾丸生精细胞凋亡及Caspase-3,Bcl-2和Bax基因表达的影响

为了研究铅致小鼠睾丸生精细胞凋亡及其对Caspase-3,Bax和Bcl -2基因表达的影响.25只雄性小鼠随机分成5组:0h对照组、12h染铅组、24h染铅组、36h染铅组和48h染铅组,每组5只,实验组按照100mg/kg的剂量腹腔注射醋酸铅溶液,5组小鼠分别于0h、12h、24h、36h、48h后脊柱拉断处死,取其睾丸组织,用苏木精-伊红染色及免疫组化技术检测睾丸组织细胞凋亡及凋亡相关蛋白Caspase -3,Bcl -2和Bax的表达.结果显示:细胞凋亡相关基因Caspase -3,Bcl -2和Bax的表达较对照组差异显著,Caspase -3和Bax在染铅毒后表达量一直上升,Bcl -2的表达量一直下降,差异性随染铅时间的不同而有变化.铅负荷至一定程度时可致小鼠睾丸细胞凋亡,且呈一定量效关系(P＜0.01),这种作用可能与Bcl -2基因低表达和Caspase-3与Bax基因高表达有关.     

Apoptosis in the nervous system

Neuronal apoptosis sculpts the developing brain and has a potentially important role in neurodegenerative diseases. The principal molecular components of the apoptosis programme in neurons include Apaf-1 (apoptotic protease-activating factor 1) and proteins of the Bcl-2 and caspase families. Neurotrophins regulate neuronal apoptosis through the action of critical protein kinase cascades, such as the phosphoinositide 3-kinase/Akt and mitogen-activated protein kinase pathways. Similar cell-death-signalling pathways might be activated in neurodegenerative diseases by abnormal protein structures, such as amyloid fibrils in Alzheimer's disease. Elucidation of the cell death machinery in neurons promises to provide multiple points of therapeutic intervention in neurodegenerative diseases.     

miRNA-125a 靶向调控 Bcl-2 对癫痫大鼠神经元凋亡的影响

摘要:目的 探讨 miRNA-125a 靶向调控 Bcl-2 对癫痫大鼠神经元凋亡的影响。 方法 选择清洁级 SD 雄性大鼠32 只随机分为正常对照组( A 组) 、癫痫组( B 组) 、miRNA-125a antagomir control 组( C 组) 和 miRNA-125a antagomir组( D 组) 。 qRT-PCR 检测各组大鼠脑组织 miRNA-125a 表达水平;HE 检测各组大鼠脑海马组织 CA-1 区病理形态学改变;TUNEL 法检测脑海马 CA-1 区神经元细胞凋亡数;Western blot 和 qRT-PCR 法检测各组大鼠脑组织中 Bcl-2的表达水平;荧光素酶活性检测 miRNA-125a 与 Bcl-2 的靶向关系。 结果 与 A 组相比,B 组和 C 组大鼠脑组织miRNA-125a 表达升高,差异具有统计学意义( P<0. 05) ;A 组海马细胞排列整齐,细胞形态结构及层次清晰完整,核仁明显,间质无水肿;B 组可见坏死灶,细胞排列紊乱,细胞核固缩,核仁消失,细胞间隙增宽出现水肿;TUNEL 结果显示,B 组、C 组和 D 组脑海马神经元凋亡细胞数明显高于 A 组,而大鼠脑组织 Bcl-2 mRNA 及蛋白表达降低。 D 组miRNA-125a 表达与 C 组相比降低而 Bcl-2 表达增加( P<0. 05) ,且 D 组大鼠脑组织水肿现象明显减轻,海马细胞排列紊乱现象有所改善。 荧光素酶报告基因实验结果显示,miRNA-125a 和 Bcl-2 能够靶向结合。 结论 癫痫模型大鼠脑组织 miRNA-125a 可通过调控 Bcl-2 表达,进一步导致脑海马神经元损伤及大量神经元细胞凋亡;抑制 miRNA-125a 的表达水平可改善癫痫大鼠神经元损伤。     

DRP-1-mediated mitochondrial fragmentation during EGL-1-induced cell death in C. elegans

Genetic analyses in Caenorhabditis elegans have been instrumental in the elucidation of the central cell-death machinery, which is conserved from C. elegans to mammals. One possible difference that has emerged is the role of mitochondria. By releasing cytochrome c, mitochondria are involved in the activation of caspases in mammals. However, there has previously been no evidence that mitochondria are involved in caspase activation in C. elegans. Here we show that mitochondria fragment in cells that normally undergo programmed cell death during C. elegans development. Mitochondrial fragmentation is induced by the BH3-only protein EGL-1 and can be blocked by mutations in the bcl-2-like gene ced-9, indicating that members of the Bcl-2 family might function in the regulation of mitochondrial fragmentation in apoptotic cells. Mitochondrial fragmentation is independent of CED-4/Apaf-1 and CED-3/caspase, indicating that it occurs before or simultaneously with their activation. Furthermore, DRP-1/dynamin-related protein, a key component of the mitochondrial fission machinery, is required and sufficient to induce mitochondrial fragmentation and programmed cell death during C. elegans development. These results assign an important role to mitochondria in the cell-death pathway in C. elegans.     

线粒体参与了三尖杉酯碱诱导的HL-60细胞凋亡

用流式光度术研究了三尖杉酯碱诱导人早幼粒白血病ＨＬ－６０细胞及其转染了ｂｃｌ－２基因的细胞株ＨＬ－６０／Ｂｃｌ－２线粒体膜电势的变化,数据表明线粒体损伤介导了ＨＴ诱导的ＨＬ－６０细胞的凋亡过程。