胞内钙的稳态调节

胞内钙的稳态调节主要有两方面：质膜钙运转调节和胞内钙库的调节。质膜钙运转包括质膜钙泵,质膜钙通道和Ｎａ＾＋／Ｃａ＾２＋交换的调节作用。胞内钙库的调节受第二信使操纵,钙库有其特异的库蛋白分子参与钙的贮存、诱导释放和重新摄取过程。这两方面的协同作用精确保证了细胞溶质中自由钙离子的稳定水平。     

B细胞稳态的信号调节

在人类,65%的骨髓产生的B细胞是自身反应性的,它们大部分在骨髓中被克隆删除了。但有些B细胞通过免疫无力的方式逃脱了这种克隆删除到达外周,产生抗自身的抗体。研究表明,在鼠和人类中,B细胞存活时间过长是引发自身性免疫病的原因之一。B细胞的过度活化将导致自身反应性B细胞的产生和破坏自身免疫耐受,引起自身免疫性疾病或肿瘤;但B细胞的活化不足将使B细胞数量大大减少,抗原应答能力降低,从而使适应性免疫应答失衡。细胞因子和其他信号分子对B细胞稳态的调节是十分严密的,它们或调节B细胞的发育、成熟和分化,或调节B细胞向外周的迁移,或通过调节B细胞周期而使B细胞停留在特定时期,从而使B细胞避免凋亡,或通过调节抗凋亡蛋白或凋亡蛋白而决定B细胞的生存或死亡。本文就细胞因子、转录因子、蛋白激酶等信号分子对B细胞稳态的调节做一综述。     

神经元钙稳态失衡在阿尔茨海默病发病中的进展

淀粉样蛋白的沉积与Tau蛋白磷酸化是阿尔茨海默病发病的关键分子机制,神经元胞内钙离子的变化可影响其生成和代谢;另一方面,这些蛋白的改变会进一步导致神经元钙稳态的失调,致使突触损伤、神经细胞凋亡及认知功能下降。本文就神经元钙稳态失衡在阿尔茨海默病发病中的进展进行综述。     

钙稳态失衡与癌细胞抑制

细胞胞浆钙离子浓度必须处于严格的调控之中,钙稳态失调必将导致细胞严重损伤或死亡（凋亡或坏死）.综述了钙稳态失调在外界因素引起细胞死亡中的作用、直接钙稳态失调的细胞死亡效应、以及钙离子在细胞凋亡中的作用,并讨论了上述作用的机制,最后在总结基础上提出了一种抑癌新途径——选择性引发癌细胞钙稳态失衡.     

神经元钙稳态失衡在阿尔茨海默病发病中的进展木

淀粉样蛋白的沉积与Tau蛋白磷酸化是阿尔茨海默病发病的关键分子机制,神经元胞内钙离子的变化可影响其生成和代谢;另一方面,这些蛋白的改变会进一步导致神经元钙稳态的失调,致使突触损伤、神经细胞凋亡及认知功能下降.本文就神经元钙稳态失衡在阿尔茨海默病发病中的进展进行综述.     

钙调蛋白结合蛋白通过调节细胞骨架稳定性影响肿瘤细胞运动能力

轻链钙调蛋白结合蛋白（light-chain Caldesmon,l-CaD）是一种重要的肌动蛋白结合蛋白,普遍存在于众多非肌肉细胞中。体外研究证明,l-CaD能通过与肌动蛋白的结合起到促进原肌动蛋白（G-actin）聚合、稳定肌动蛋白纤维（F-actin）结构的作用。在磷酸化作用下,l-CaD能从肌动蛋白纤维上脱离并促进肌动蛋白纤维的解聚。该研究拟考察l-CaD在细胞内对细胞肌动蛋白骨架的调节作用,阐明l-CaD对细胞运动能力的影响,作者将天然低表达l-CaD的人源性乳腺癌细胞MCF-7作为细胞模型,在MCF-7胞内以基因转染的方式高表达外源野生型l-CaD及其磷酸化突变株A1234-CaD（不可磷酸化CaD）、D1234-CaD（完全磷酸化CaD）。首先,通过激光共聚焦扫描,探讨了l-CaD对细胞骨架重排的调节;其次,通过细胞迁移transwell阵列,检测了l-CaD对细胞迁移能力的影响;最后,在单细胞层次上测定了细胞基底牵张力、胰酶刺激下的细胞基底脱附能力,并进一步检测了l-CaD对细胞迁移子过程中细胞伸张、收缩的影响。研究结果显示,l-CaD在胞内对细胞骨架的形成有显著的调控作用。非磷酸化l-CaD主要富集在细胞骨架上,增强了细胞骨架的强度,导致细胞基底牵张力以及对胰酶的耐受性增强,但对细胞的迁移能力有显著的抑制作用;磷酸化l-CaD跟细胞骨架结合能力很弱,对细胞的运动能力没有显著影响。通过磷酸化,l-CaD起到了一个“蛋白开关”的作用,通过控制细胞骨架的解聚、重排来调节细胞的运动能力。     

钙蛋白酶的结构及活性调节

钙蛋白酶广泛存在于各组织,广泛表达的钙蛋白酶有两种,钙蛋白酶Ⅰ和钙蛋白酶Ⅱ,它们激活所需的Ca^2＋浓度不同.这两种酶都有大、小两个亚基,分子质量分别为80 ku和30 ku.大亚基有4个结构域,小亚基由2个结构域构成.新近还发现了几种组织特异表达的钙蛋白酶.钙蛋白酶抑制蛋白是钙蛋白酶的内源抑制蛋白,它由5个结构域组成,其中4个为重复序列,均具有独立抑制钙蛋白酶活性的功能.体内钙蛋白酶活性受到严格调控,贴膜反应可以降低钙蛋白酶对Ca^2＋的依赖性,膜磷脂头部所带的磷酸基团与激活作用有关,自溶也可以降低对Ca^2＋的依赖,而钙蛋白酶抑制蛋白则起专一的抑制作用.     

星形胶质细胞在血脑屏障发育与稳态维持中的作用机制

血脑屏障(blood-brain barrier, BBB)由脑微血管内皮细胞及包绕内皮细胞的基膜、周细胞和星形胶质细胞的足突构成,它将血液与脑组织分隔开来,从而维持神经功能包括神经环路、突触连接和重塑等微环境的稳定。BBB稳态失衡与包括神经退行性疾病在内的许多中枢神经系统疾病有关,但目前BBB稳态维持与失衡的机制尚不清楚。星形胶质细胞作为BBB的组成成分,也是神经血管单元中联系神经元与脑微血管的枢纽,在BBB发育特别是BBB稳态维持中起重要作用。本文在简要介绍BBB的发育过程之后,综述了星形胶质细胞诱导BBB发育、成熟及其在BBB稳态维持中的作用和机制的研究进展,并指出了与BBB稳态失衡有关的A1型星形胶质细胞异质性的概念,以期为深入研究BBB稳态维持机制及加深理解BBB稳态失衡诱发神经退行性疾病提供新启示。     

钙网蛋白与凋亡细胞清除

钙网蛋白(calreticulin, CRT)是细胞内质网/肌浆网中主要的Ca2 结合蛋白,具有细胞内钙稳态调节、分子伴侣、抗原提呈等多种生物学功能.近来的研究发现, CRT在机体对凋亡细胞的有效识别、清除过程中起关键作用.     

膜钠钙交换蛋白和过氧化氢交互作用对细胞内钙稳态调控

本研究旨在阐明过氧化氢（H2O2）和膜钠钙交换蛋白相互作用对胞浆钙[Ca^2 ],的调控。在稳定表达钠钙交换蛋白CK1．4细胞上,用^45Ca同位素液闪计数法测定钠钙交换蛋白的活性;用fura-2荧光探针和340／380nm双兴奋波长荧光影像技术测定钙释放和[Ca^2 ]i。两因素两水平和三因素两水平正交分析表明10mmol/L H2O2与150mmol/L细胞外钠（[Na^ ]o,1mmol/L细胞外钙[Ca^2 ],相互作用或10mmol/L H2O2分别与150mmol/L[Na ]。或1[Na^ ]。激活钠钙交换蛋白,排出细胞内钙离子,降低[Ca2 ]i。当[Na^ ]。递减至0mmol/L时,10mmol/L H2O2直接抑制钠钙交换蛋白的活性,增加钙释放和升高[Ca2 ]i.在不同[Na^=},梯度中,10mmol/LH2O2对膜的钠钙交换活动和[Ca2 ],起双重调节作用,即抑制或增加钙内流和[Ca^2=]i.10mmol/L H2O2与膜钠钙交换蛋白和[Ca2 ]。相互作用对钠钙交换活动方向,钙释放和[Ca^2_]起负反馈谳节作用。     

Ganglioside Function in Calcium Homeostasis and Signaling

Ganglioside function in eukaryotic cells encompasses a variety of modulatory interactions related to both development and mature cellular behavior. In relation to the nervous system this includes induction of neurite outgrowth and trophic/neuroprotective phenomena; more generally this applies to ganglioside effects on receptor function, adhesion reactions, and signal transduction mechanisms in neural and extraneural systems. Underlying many of these trophic effects are ganglioside-induced changes in cellular calcium, accomplished through modulation of Ca²⁺ influx channels, Ca²⁺ exchange proteins, and various Ca²⁺-dependent enzymes that are altered through association with gangliosides. A clear distinction needs to be drawn between intrinsic functions of gangliosides as naturally expressed by the cell and activities created by application of exogenous ganglioside(s) that may or may not reflect natural function. This review attempts to summarize findings in this area and point to possible future directions of research.     

Bacterial Calcium Carbonate Precipitation in Cave Environments: A Function of Calcium Homeostasis

To determine if microbial species play an active role in the development of calcium carbonate (CaCO ₃ ) deposits (speleothems) in cave environments, we isolated 51 culturable bacteria from a coralloid speleothem and tested their ability to dissolve and precipitate CaCO ₃ . The majority of these isolates could precipitate CaCO ₃ minerals; scanning electron microscopy and X-ray diffractrometry demonstrated that aragonite, calcite and vaterite were produced in this process. Due to the inability of dead cells to precipitate these minerals, this suggested that calcification requires metabolic activity. Given growth of these species on calcium acetate, but the toxicity of Ca ²⁺ ions to bacteria, we created a loss-of-function gene knock-out in the Ca ²⁺ ion efflux protein ChaA. The loss of this protein inhibited growth on media containing calcium, suggesting that the need to remove Ca ²⁺ ions from the cell may drive calcification. With no carbonate in the media used in the calcification studies, we used stable isotope probing with C ¹³ O ₂ to determine whether atmospheric CO ₂ could be the source of these ions. The resultant crystals were significantly enriched in this heavy isotope, suggesting that extracellular CO ₂ does indeed contribute to the mineral structure. The physiological adaptation of removing toxic Ca ²⁺ ions by calcification, while useful in numerous environments, would be particularly beneficial to bacteria in Ca ²⁺ -rich cave environments. Such activity may also create the initial crystal nucleation sites that contribute to the formation of secondary CaCO ₃ deposits within caves.     

线粒体和细胞内钙自稳平衡

线粒体对胞浆钙信号调节作用的研究已经历较长时间.近年,随着研究方法和技术的不断改进,发现在绝大多数生理条件下,线粒体都能参与胞内钙通信过程.线粒体可感受其周围钙微区的存在从而摄取钙,又可以通过钠-钙交换和大分子孔道将钙释放出来,因此可以调节胞浆钙信号的时空特性,影响相关的细胞功能.但是,由于技术上的局限性,目前的研究仍然存在模糊不清和自相矛盾之处,有待于进一步研究.     

Excitatory Amino Acid-Mediated Cytotoxicity and Calcium Homeostasis in Cultured Neurons

Abstract: A large body of evidence suggests that disturbances of Ca²⁺ homeostasis may be a causative factor in the neurotoxicity induced by excitatory amino acids (EAAs). The route or routes by which an increase in intracellular calcium concentration ([Ca²⁺]_i) is mediated in vivo are presently not clarified. This may partly reflect the complexity of intact nervous tissue in combination with the relative unspecific action of the available “calcium antagonists,” e.g., blockers of voltage-sensitive calcium channels. By using primary cultures of cortical neurons as a model system, it has been found that all EAAs stimulate increases in [Ca²⁺]_i but via different mechanisms. By using the drug dantrolene, it has been shown that 2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionate (AMPA) apparently exclusively stimulates Ca²⁺ influx through agonist-operated calcium channels and voltage-operated calcium channels. Increased [Ca²⁺]_i due to exposure to kainate (KA) is for the major part caused by influx, as in the case of AMPA, but a small part of the increase in [Ca²⁺]_i may be attributed to a release of Ca²⁺ from intracellular stores. Quisqualate (QA) stimulates Ca²⁺ release from an intracellular store that is independent of Ca²⁺ influx; presumably this store is activated by inositol phosphates. The increase in [Ca²⁺]_i due to exposure to glutamate or N-methyl-d -aspartate (NMDA) may be compartmentalized into three components, one of which is related to influx and the other two to Ca²⁺ release from internal stores. Only one of the latter stores is dependent on Ca²⁺ influx with regard to release of Ca²⁺, whereas the other is activated by some other second messengers or, alternatively, directly coupled to the receptor. In muscles dantrolene is known to inhibit Ca²⁺ release from the sarcoplasmic reticulum, and also in neurons dantrolene inhibits an equivalent release from one or more hitherto unidentified internal Ca²⁺ pool(s). By using this drug it has been possible to show to what extent these Ca²⁺ stores are involved in the toxicity observed subsequent to exposure to the EAAs. It turned out that dantrolene, even under conditions allowing Ca²⁺ influx, inhibited toxicity induced by QA, NMDA, and glutamate, whereas that induced by AMPA or KA was unaffected. In combination with the findings that dantrolene inhibited release from the intracellular stores activated by QA, NMDA, and glutamate, it may be concluded that Ca²⁺ influx per se is not the primary event causing toxicity following exposure to these EAAs in these neurons. However, it may certainly be involved in the cases of toxicity induced by AMPA and KA. Finally, it should be pointed out that this model only serves as a much simplified working hypothesis and that the situation in vivo is much more complex.     

Calcium Wave Promotes Cell Extrusion

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丙二醛对大鼠海马神经元结构的破坏和钙离子稳态的影响

脂质过氧化中间产物丙二醛(Malondialdehyde,MDA)在生物体内表现了广泛的生物毒性,MDA也是机体过度训练和运动性疲劳的重要生理指标.采用光学显微镜和透射式电子显微镜观察不同浓度MDA作用后海马神经元形态和超微结构的变化,并采用荧光分光光度法测定原代培养的海马神经元中Ca2+-ATPase活性的变化和胞质游离钙离子水平的变化,探讨MDA对海马神经元形态和结构上的破坏及神经元钙离子稳态的影响.在光镜下可观察到MDA作用下神经元突触变短,胞体肿胀,出现细胞死亡或凋亡的形态特征;在电镜下可观察到线粒体结构的明显破坏,内膜上的嵴颗粒减少或消失;同时MDA还通过抑制质膜Ca2+-ATPase的活性和其它的途径,破坏神经元胞质游离Ca2+稳态.结果表明,MDA可通过破坏海马神经元的结构和影响胞质中钙离子稳态,破坏神经元的生理功能,在机体运动性中枢疲劳形成中可能发挥重要作用.     

The Role of Taurine in the Central Nervous System and the Modulation of Intracellular Calcium Homeostasis

The effects of taurine in the mammalian nervous system are numerous and varied. There has been great difficulty in determining the specific targets of taurine action. The authors present a review of accepted taurine action and highlight recent discoveries regarding taurine and calcium homeostasis in neurons. In general there is a consensus that taurine is a powerful agent in regulating and reducing the intracellular calcium levels in neurons. After prolonged L-glutamate stimulation, neurons lose the ability to effectively regulate intracellular calcium. This condition can lead to acute swelling and lysis of the cell, or culminate in apoptosis. Under these conditions, significant amounts of taurine (mM range) are released from the excited neuron. This extracellular taurine acts to slow the influx of calcium into the cytosol through both transmembrane ion transporters and intracellular storage pools. Two specific targets of taurine action are discussed: Na⁺-Ca²⁺ exchangers, and metabotropic receptors mediating phospholipase-C.     

构建钙荧光探针细胞用于探究胞浆和线粒体钙对ATP刺激的响应

目的:构建表达基因编辑钙探针(GECIs)的细胞系HeLa-GECIs,探究细胞应答外界ATP刺激中钙离子在细胞内的响应和变化。方法:分别用能够直接通过荧光强度反映细胞胞浆内和线粒体内钙离子相对浓度的2种钙探针cyto-GCaMP6和4mt-GCaMP6感染HeLa细胞,获得2种表达钙离子探针的HeLa细胞系;在感染了2种腺病毒探针24 h后,用共聚焦荧光显微镜检测荧光探针在HeLa细胞内的表达情况;在表达2种钙探针的细胞的培养基中加入外源ATP,用Time-lapse成像动态观测技术观察HeLa细胞内钙离子对外环境中ATP的响应。结果:共聚焦荧光显微镜观察,确定95%以上的细胞表达了对应的钙离子指示荧光探针;Time-lapse成像动态观测技术观察发现,在细胞培养基中加入ATP后,细胞胞浆钙探针荧光强度瞬时(3～6 s)升至10倍,200 s后逐渐降低到基础水平;线粒体钙到达峰值(4倍)的时间稍滞后(5～8 s),并且回落更慢,300 s时至1.5倍。在ATP受体P2X7抑制剂A438079预处理的实验组,上述胞浆钙和线粒体钙浓度上升不明显。结论:构建了能在活体细胞内通过荧光探针实时监测钙离子响应胞外ATP刺激的细胞实验体系,为进一步深入探究ATP等危险信号导致细胞的炎性损伤机制奠定了基础。     

A Role for Astroglial Calcium in Mammalian Sleep and Sleep Regulation

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