介导心肌肥大的一条新的信号通路--Calcineurin通路

心肌肥大是心肌细胞对外界刺激,如工作负荷、神经体液因子及内在心肌蛋白遗传突变一种基本应答。已知胞内Ｃａ＾２＋浓度升高在各种刺激诱导心肌肥大的信号传递中起重要作用,但对Ｃａ＾２＋信号下游的传递机制一直不甚清楚。新近研究证实,由Ｃａ＾２＋活化的钙调神经磷酸酶（ＣａＮ）在心肌肥大的信号传递中起重要作用,基可能是Ｃａ＾２＋信号致肥大基因活化的偶联环节。抑制ＣａＮ活性可阻滞各种因素诱导的心肌肥大发生与发展,     

钙调神经磷酸酶在血管紧张素Ⅱ刺激的心脏成纤维细胞增殖中的作用

本研究观察了钙调神经磷酸酶（ＣａＮ）在血管坚张素Ⅱ（ＡｎｇⅡ）刺激的大鼠心脏成纤维细胞增殖中的作用。在培养的大鼠心脏成纤维细胞上,应用双波长荧光 计检测Ｆｕｒａ－２标记的细胞游离Ｃａ＾２＋浓度;应用对硝基苯磷酸（ＰＮＰＰ）作底物测定钙调神经磷酸酶（ＣａＮ）活性;根据＾３Ｈ－胸腺嘧啶掺入法评估ＣａＮ特异性抑制剂环胞素Ａ（ＣｓＡ）对ＡｎｇⅡ刺激的心脏成纤维细胞ＤＮＡ合成的影响。结果表明,ＡｎｇⅡ（１０     

跨膜Ca^2＋梯度对肌质网Ca^2＋—ATP酶调节的特异性

我们曾报道跨膜Ｃａ＾２＋梯度可通过膜脂影响肌质网Ｃａ＾２＋－ＡＴＰ酶的构象和活性。本文就跨膜Ｃａ＾２＋－ＡＴＰ酶的构象和活性。本文就跨膜Ｃａ＾２＋梯度对肌质网Ｃａ＾２＋－ＡＴＰ酶的调节是否具有特异性作进一步研究。结果表明这种特异性表现在两方面：一是跨膜Ｃａ＾２＋梯度对肌质网Ｃａ＾２＋－ＡＴＰ酶功能的调节不能归结于跨膜Ｃａ＾２＋深度梯度所导致的膜电位的作用,离子载体ＦＣＣＰ可消除跨膜电位但并不影响肌     

平滑肌收缩中Ca^2＋敏感性调节的机理

多种激动剂增加细胞器对Ｃａ＾２＋的敏感性,即Ｃａ＾２＋的敏感性,即Ｃａ＾２＋敏感化作用。激动剂的这种作用可能是通过Ｇ蛋白,经信号分子花生四烯酸和二酰基甘油,反暹号传递到肌球蛋白轻链磷酸酶（ＭＬＣＰ）,增加肌球蛋白磷酸化。细胞内游离Ｃａ＾２＋升高到一定程度,ｃａｌｍｏｄｕｌｉｎ激酶Ⅱ活化,导致ＭＬＣＫ磷酸化,降低了其对Ｃａ＾２＋－ｃａｌｍｏｄｕｌｉｎ亲和力,ＭＬＣＫ对Ｃａ＾２＋敏感性降低,即Ｃａ＾２     

线粒体Ca^2＋转运与细胞代谢调节

线粒体具有一套完整的Ｃａ＾２＋转运系统,包括两条摄取途径和三条释放途径。生理条件下,它们在细胞胞质与线粒体钙稳态维持以及细胞能量代谢中起重要作用,线粒体从胞质摄取的Ｃａ＾２＋可激活某些Ｃａ＾２＋敏感的呼吸酶和代谢过程。病理条件下,线粒体Ｃａ＾２＋转运发生紊乱,通过线粒体通透性转换导致细胞坏死或凋亡。     

钙在植物乙烯生成及信号传递中的生理作用

Ｃａ＾２＋对植物乙烯生成的调节与作用位点有关,胞外Ｃａ＾２＋在维持质膜功能的同时,抑制乙烯生成,延缓衰老;过量Ｃａ＾２＋进入胞质,胞内Ｃａ＾２＋促进乙烯生成和衰老。内源ＣａＭ与乙烯生成关系密切,介入了乙烯代谢和外源激素对乙烯的调控。此外,Ｃａ＾２＋是乙烯信号传递所必需的。     

钙离子对江浙蝮蛇毒酸性磷脂酶A2结构与功能的影响

钙离子在江浙蝮蛇毒酸性磷脂酶Ａ２中的作用是多方面的,它不仅能够引起酸性磷脂酶Ａ２在溶液中构象的变化,而且对该酶活性有较大的影响,Ｃａ＾２＋为酶活力所必需,当Ｃａ＾２＋浓度达到０．０６ｍｍｏｌ／Ｌ时,酶表现出很的活力;Ｃａ＾２＋浓度超过０．５ｍｍｏｌ／Ｌ时,催化反应出现一个明显的延滞期。化学修饰表明Ｈｉｓ４７在表现活力方面起重要作用,Ｃａ＾２＋的存在可降低其修饰反应的速度,提示这是由于Ｃａ＾２＋引起     

牛磺酸对心肌细胞钙离子的调节作用

牛磺酸占心肌游离氨基酸的５０％以上,它对心肌细胞许多依赖于Ｃａ＾２＋的生理两全是现象具有明显的调节作用。牛磺酸能增加高亲和力Ｃａ＾２＋转驼系统转运Ｃａ＾２＋的量和速度,对要和力Ｃａ＾２＋转运系统的调节作用依胞外Ｃａ＾２＋浓度的不同而不同,具有稳态调节细胞内的Ｃａ＾２＋作用;另外,牛磺酸尚能抑制各种原因经起的胞内Ｃａ＾２＋超负荷,显示其具有细胞保护作用。     

水分胁迫及复水过程中小麦幼苗叶片内Ca^2＋的定位

展现了冬小麦幼苗在干旱胁迫及干旱后复水过程中叶肉细胞内Ｃａ＾２＋的动态分布：在正常水分条件下生长的小麦幼苗,其细胞中的Ｃａ＾２＋主要位于液泡内,同时,细胞间隙中有大量的Ｃａ＾２＋分布。在水分胁迫下,随着胁迫时间的加长,液泡和细胞间隙的Ｃａ＾２＋逐渐进入细胞质,导致细胞质中自由Ｃａ＾２＋浓度过高,并对细胞造成伤害。复水后,细胞质中高浓度Ｃａ＾２＋迅速排入液泡和细胞间隙,细胞质中Ｃａ＾２＋浓度又基本恢     

细胞质膜上的Ca^2＋受体

以前就有过设想；甲状旁腺细胞表面的Ｃａ＾２＋受体可感受细胞外Ｃａ＾２＋浓度变化并起应答反应。最近克隆到的与Ｇ蛋白偶联的Ｃａ＾２＋受体证实了上述观点。Ｃａ＾２＋受体可调节不同细胞活性。Ｃａ＾２＋受体的发现为新药设计提供了新的靶分子物质。     

Redox control of calcineurin by targeting the binuclear Fe(2+)-Zn(2+) center at the enzyme active site.

The interaction of protein serine/threonine phosphatase calcineurin (CaN) with superoxide and hydrogen peroxide was investigated. Superoxide specifically inhibited phosphatase activity of CaN toward RII (DLDVPIPGRFDRRVSVAAE) phosphopeptide in tissue and cell homogenates as well as the activity of the enzyme purified under reducing conditions. Hydrogen peroxide was an effective inhibitor of CaN at concentrations several orders of magnitude higher than superoxide. Inhibition by superoxide was calcium/calmodulin-dependent. Nitric oxide (NO) antagonized superoxide action on CaN. We provide kinetic and spectroscopic evidence that native, catalytically active CaN has a Fe(2+)-Zn(2+) binuclear center in its active site that is oxidized to Fe(3+)-Zn(2+) by superoxide and hydrogen peroxide. This oxidation is accompanied by a gain of manganese dependence of enzyme activity. CaN isolated by a conventional purification procedure was found in the oxidized, ferric enzyme form, and it became increasingly dependent on divalent cations. These results point to a complex redox regulation of CaN phosphatase activity by superoxide, which is modified by calcium, NO, and superoxide dismutase.     

Expression of calcineurin and its interacting proteins in epileptic fowl

Calcineurin (CaN), a Ca2+-calmodulin (CaM)-dependent protein phosphatase, is important for Ca2+-mediated signal transduction. The main objective of this study was to examine the potential role of CaN in epileptic brain and its involvement in neuronal apoptosis. We investigated CaN expression and its interaction with various signaling molecules in normal, carrier and epileptic brain tissues of chicken. Our results revealed higher Ca2+-CaM-dependent phosphatase activity of CaN and a correspondingly strong immunoreactive band of CaN A in epileptic and carrier brain samples compared with normal brain. Furthermore, immunohistochemical analysis showed a higher level of expression of CaN in epileptic brain tissue. However, the intensity of immunoreactivity was less in carrier than epileptic brain. We observed that the interaction of CaN with m-calpain and micro-calpain was strong in carrier and epileptic chickens compared with that in normal birds. In addition, the interaction of CaN with Bcl-2, caspase-3 and p53 was greater in carrier and epileptic fowl than in normal chickens. The greater interaction of CaN with various apoptotic factors in epileptic chickens adds to our understanding of the mechanism of CaN signaling in neuronal apoptosis.     

Inhibition of excitatory neuronal cell death by cell-permeable calcineurin autoinhibitory peptide

In glutamate-mediated excitatory neuronal cell death, immunosuppressants (FK506, Cys-A) are powerful agents that protect neurons from apoptosis. Immunosuppressants inhibit two types of enzyme, calcium/calmodulin-dependent protein phosphatase (calcineurin: CaN), and peptidyl-prolyl cis-trans-isomerase (PPIase) activity such as the FKBP family. In this study, we used a protein transduction approach to determine the functional role of CaN and to produce a potential therapeutic agent for glutamate-mediated neuronal cell death. We created a novel cell-permeable CaN autoinhibitory peptide using the 11 arginine protein transduction domain. This peptide was highly efficient at transducing into primary culture neurons, potently inhibited CaN phosphatase activities, and inhibited glutamate-mediated neuronal cell death. These results showed that CaN plays an important role in excitatory neuronal cell death and cell-permeable CaN autoinhibitory peptide could be a new drug to protect neurons from excitatory neuronal death.     

钙调神经磷酸酶的研究进展

钙调神经磷酸酶(CaN)是一种受Ca²⁺/钙调素调节的丝/苏氨酸蛋白磷酸酶,广泛存在于哺乳动物的组织细胞中,作为Ca²⁺信号下游的一种效应分子,参与多种细胞功能的调节.在T细胞活化的信号传导中起到调节枢纽的作用;在神经递质的释放、突触可塑性方面亦有重要的调节作用.新近的研究表明,CaN在心肌肥厚的发生发展中起到中心作用.对CaN的分子结构、酶学特性、组织分布、信号传导及生物学功能方面的研究进展进行了介绍.     

Inactivation of calcineurin by hydrogen peroxide and phenylarsine oxide. Evidence for a dithiol-disulfide equilibrium and implications for redox regulation.

Calcineurin (CaN) is a Ca2+-and calmodulin (CaM)-dependent serine/threonine phosphatase containing a dinuclear Fe-Zn center in the active site. Recent studies have indicated that CaN is a possible candidate for redox regulation. The inactivation of bovine brain CaN and of the catalytic CaN A-subunit from Dictyostelium by the vicinal dithiol reagents phenylarsine oxide (PAO) and melarsen oxide (MEL) and by H2O2 was investigated. PAO and MEL inhibited CaN with an IC50 of 3-8 microM and the inactivation was reversed by 2, 3-dimercapto-1-propane sulfonic acid. The treatment of isolated CaN with hydrogen peroxide resulted in a concentration-dependent inactivation. Analysis of the free thiol content performed on the H2O2 inactivated enzyme demonstrated that only two or three of the 14 Cys residues in CaN are modified. The inactivation of CaN by H2O2 could be reversed with 1,4-dithiothreitol and with the dithiol oxidoreductase thioredoxin. We propose that a bridging of two closely spaced Cys residues in the catalytic CaN A-subunit by PAO/MEL or the oxidative formation of a disulfide bridge by H2O2 involving the same Cys residues causes the inactivation. Our data implicate a possible involvement of thioredoxin in the redox control of CaN activity under physiological conditions. The low temperature EPR spectrum of the native enzyme was consistent with a Fe3+-Zn2+ dinuclear centre. Upon H2O2-mediated inactivation of the enzyme no significant changes in the EPR spectrum were observed ruling out that Fe2+ is present in the active enzyme and that the dinuclear metal centre is the target for the oxidative inactivation of CaN.     

Blocking gastrin and CCK-B autocrine loop affects cell proliferation and apoptosis in vitro

Since its initial discovery as Ca²⁺/calmodulin (CaM)-dependent serine/threonine protein phosphatase, calcineurin (CaN) has been extensively studied in many mammalian tissues. CaN has been shown to be involved in various biological and Ca²⁺-dependent signal transduction pathways. Over the last decade, our laboratory has been interested and has carried out numerous experiments on this specific protein phosphatase. While, a lot of research has been performed studying CaN’s involvement in ischemia, the immune system, and various mammalian tissues, not much is known about the potential role of CaN in various eye diseases. This review focuses on the studies that have been carried out in our laboratory on CaN, and specifically CaN’s involvement in the eye. We demonstrated that CaN is localized in various eye tissues (cornea, iris, ciliary body, vitreous body, retina, choroid, sclera, and optic nerve) and that both its protein expression and activity were observed in high amounts in the retina, optic nerve and cornea. Recently, we have cloned and characterized the CaN A and B subunits in the bovine retina. These initial findings suggest that CaN may play a potential role in visual transduction and various ocular diseases, including cancer.     

Increased expression of calcineurin in human colorectal adenocarcinomas

Colorectal cancer (CRC) is the third most common cause of cancer death in the Western world. Calcineurin (CaN), a Ca2+/calmodulin (CaM)-dependent protein phosphatase, is important for Ca2+-mediated signal transduction. The main objective of this study is to examine the potential role of Ca2+/CaM-dependent protein phosphatase in both normal and in invasive tumor components of human samples. In this study, we carried out 45 cases of CaN activity, 13 cases of CaN protein expression by Western blot analysis, and 6 cases for immunohistochemical analysis in both normal and invasive tumor components of human samples. Immunohistochemical analysis revealed that strong cytoplasmic staining of varying intensity was observed in colon tumors of all patients compared to normal mucosa. In addition, Western blot analysis revealed a prominent overexpressed immunoreactive band with an apparent molecular mass of 60 kDa catalytic alpha subunit (CaN A) as well as CaN Aalpha and beta in colon tumor samples. Elevated CaN protein expression appears to be a possible link between Ca2+ signaling and oncogenic processes.     

Downregulation of calcineurin activity in cervical carcinoma

Background  

Calcineurin (CaN) is an important serine-threonine phosphatase (PP2B), which plays a crucial role in calcium-calmodulin mediated signal transduction events. Calcineurin has been implicated in pathogenesis of various diseases cardiac hypertrophy, diabetic neuropathy and Alzheimer's, however its role in neoplasia remains unclear.