Myocilin Regulates Cell Proliferation and Survival

Myocilin, a causative gene for open angle glaucoma, encodes a secreted glycoprotein with poorly understood functions. To gain insight into its functions, we produced a stably transfected HEK293 cell line expressing myocilin under an inducible promoter and compared gene expression profiles between myocilin-expressing and vector control cell lines by a microarray analysis. A significant fraction of differentially expressed genes in myocilin-expressing cells was associated with cell growth and cell death, suggesting that myocilin may have a role in the regulation of cell growth and survival. Increased proliferation of myocilin-expressing cells was demonstrated by the WST-1 proliferation assay, direct cell counting, and immunostaining with antibodies against Ki-67, a cellular proliferation marker. Myocilin-containing conditioned medium also increased proliferation of unmodified HEK293 cells. Myocilin-expressing cells were more resistant to serum starvation-induced apoptosis than control cells. TUNEL-positive apoptotic cells were dramatically decreased, and two apoptotic marker proteins, cleaved caspase 7 and cleaved poly(ADP-ribose) polymerase, were significantly reduced in myocilin-expressing cells as compared with control cells under apoptotic conditions. In addition, myocilin-deficient mesenchymal stem cells exhibited reduced proliferation and enhanced susceptibility to serum starvation-induced apoptosis as compared with wild-type mesenchymal stem cells. Phosphorylation of ERK1/2 and its upstream kinases, c-Raf and MEK, was increased in myocilin-expressing cells compared with control cells. Elevated phosphorylation of ERK1/2 was also observed in the trabecular meshwork of transgenic mice expressing 6-fold higher levels of myocilin when compared with their wild-type littermates. These results suggest that myocilin promotes cell proliferation and resistance to apoptosis via the ERK1/2 MAPK signaling pathway.     

细胞壁在植物胚胎发生中的作用

在植物的生长与发育过程中,细胞壁不仅在决定和维持细胞形态方面发挥了重要作用,而且还参与了对细胞生长与分化的调控,这种调控涉及一些细胞壁信号分子,尤其是一些细胞壁水解产物在细胞内和细胞间的转导。现对细胞壁在植物胚胎发生中的作用进行综述。     

植物中的细胞程序性死亡

细胞程序性死亡(PCD)对于维持植物的正常生长发育非常重要,目前已成为植物学研究的一个热点。本文综合评述了近年来植物PCD研究的某些进展,包括植物PCD的特征,植物的营养生长、生殖生长以及与环境互作过程中存在的各种PCD及其证据,植物PCD发生的分子机制及其调控等等。对植物PCD研究中有待进一步解决的问题和可能意义提出了自己的见解。     

Steroid Hormone Control of Cell Death and Cell Survival: Molecular Insights Using RNAi

The insect steroid hormone ecdysone triggers programmed cell death of obsolete larval tissues during metamorphosis and provides a model system for understanding steroid hormone control of cell death and cell survival. Previous genome-wide expression studies of Drosophila larval salivary glands resulted in the identification of many genes associated with ecdysone-induced cell death and cell survival, but functional verification was lacking. In this study, we test functionally 460 of these genes using RNA interference in ecdysone-treated Drosophila l(2)mbn cells. Cell viability, cell morphology, cell proliferation, and apoptosis assays confirmed the effects of known genes and additionally resulted in the identification of six new pro-death related genes, including sorting nexin-like gene SH3PX1 and Sox box protein Sox14, and 18 new pro-survival genes. Identified genes were further characterized to determine their ecdysone dependency and potential function in cell death regulation. We found that the pro-survival function of five genes (Ras85D, Cp1, CG13784, CG32016, and CG33087), was dependent on ecdysone signaling. The TUNEL assay revealed an additional two genes (Kap-α3 and Smr) with an ecdysone-dependent cell survival function that was associated with reduced cell death. In vitro, Sox14 RNAi reduced the percentage of TUNEL-positive l(2)mbn cells (p<0.05) following ecdysone treatment, and Sox14 overexpression was sufficient to induce apoptosis. In vivo analyses of Sox14-RNAi animals revealed multiple phenotypes characteristic of aberrant or reduced ecdysone signaling, including defects in larval midgut and salivary gland destruction. These studies identify Sox14 as a positive regulator of ecdysone-mediated cell death and provide new insights into the molecular mechanisms underlying the ecdysone signaling network governing cell death and cell survival.     

植物细胞的编程性死亡

植物细胞受基因调控死亡,这种编程性定位的细胞死亡具有积极的生理功能,形成有利于自身发展的结构。基因调控细胞内的酶活动,细胞器产生变化,导致细胞死亡。外部因素可调节植物基因及基因调控产物的表达。     

死亡信号传递: 叶绿体与线粒体间信号交流调控植物程序性细胞死亡

程序性细胞死亡(PCD)是生物体受遗传调控的自主细胞死亡现象, 在植物生长发育和抵抗环境胁迫中起重要作用。PCD的发生可受线粒体中活性氧(ROS)诱导。中国科学院遗传与发育生物学研究所李家洋研究组早期的研究发现了1个拟南芥(Arabidopsis thaliana)细胞死亡突变体mod1, 并暗示植物细胞中存在叶绿体与线粒体之间的信号交流调控PCD, 但其中的具体作用机制尚不清楚。最近, 他们通过大规模筛选mod1突变体的抑制突变体, 克隆了3个新的抑制基因plNAD- MDH、DiT1和mMDH1。此3个基因分别编码质体定位的NAD依赖的苹果酸脱氢酶、叶绿体被膜定位的二羧酸转运蛋白1和线粒体定位的苹果酸脱氢酶1, 突变后都可抑制mod1中ROS的积累及PCD的发生。通过对这些基因进行深入的功能分析, 他们论证了苹果酸从叶绿体到线粒体的转运对线粒体中ROS的产生及随后PCD的诱导起重要作用。该研究拓展了我们对植物细胞中细胞器间交流的认识, 为我们深入理解植物PCD发生机制提供了新线索, 是该领域的一项突破性进展。     

In Vitro Somatic Embryogenesis and Plant Regeneration in Clitoria ternatea

A sustainable plant regeneration system in vitro through somaticembryos from mature sexual embryos has been reported in Clitoriaternatea. Somatic embryos developed through callus from seedlingroots on hormone-free MS medium (MS₁). Addition of growth hormones,KN 0.5 mg dm^–3 (MS₂) or KN+1AA 0·5 mg dm^–3of each (MS₃) induced direct somatic embryos, in high frequency,on split root and hypocotyl systems. The embryogenic potentialvaried with the organ, roots or hypocotyls, and also with themedium. The morphogenetic capacity of the somatic embryos isretained for more than 2 years by subculturing at intervalsof 4 weeks on MS₃ in complete darkness. Somatic embryos, underthe appropriate subculture conditions (16 h light/8 h dark photoperiodat 24± 1 °C on media MS₃, MS₄ and MS₅), resultedin recurrent-somatic embryogenesis and was profuse at the shootand root apices of the somatic embryos. Mature somatic embryoswere transplanted to MS₁ to stimulate germination and plantletregeneration. Plantlets, developed from primary and secondaryembryos on MS₁ were successfully hardened and grown in naturaloutdoor conditions. The morphology and histology of the somaticembryo and plantlet and the culture conditions for continuousproduction of plantlets through direct somatic embryogeny arediscussed Key words: Clitoria ternatea, somatic embryos, plant regeneration     

Akt Regulates Drug-Induced Cell Death through Bcl-w Downregulation

Akt is a serine threonine kinase with a major role in transducing survival signals and regulating proteins involved in apoptosis. To find new interactors of Akt involved in cell survival, we performed a two-hybrid screening in yeast using human full-length Akt c-DNA as bait and a murine c-DNA library as prey. Among the 80 clones obtained, two were identified as Bcl-w. Bcl-w is a member of the Bcl-2 family that is essential for the regulation of cellular survival, and that is up-regulated in different human tumors, such as gastric and colorectal carcinomas. Direct interaction of Bcl-w with Akt was confirmed by immunoprecipitation assays. Subsequently, we addressed the function of this interaction: by interfering with the activity or amount of Akt, we have demonstrated that Akt modulates the amount of Bcl-w protein. We have found that inhibition of Akt activity may promote apoptosis through the downregulation of Bcl-w protein and the consequential reduction in interaction of Bcl-w with pro-apoptotic members of the Bcl-2 family. Our data provide evidence that Bcl-w is a new member of the Akt pathway and that Akt may induce anti-apoptotic signals at least in part through the regulation of the amount and activity of Bcl-w.     

Smad4 Regulates Ureteral Smooth Muscle Cell Differentiation during Mouse Embryogenesis

Proper formation of ureteral smooth muscle cells (SMCs) during embryogenesis is essential for ureter peristalsis that propels urine from the kidney to the bladder in mammals. Currently the molecular factors that regulate differentiation of ureteral mesenchymal cells into SMCs are incompletely understood. A recent study has reported that Smad4 deficiency reduces the number of ureteral SMCs. However, its precise role in the ureteral smooth muscle development remains largely unknown. Here, we used Tbx18:Cre knock-in mouse line to delete Smad4 to examine its requirement in the development of ureteral mesenchyme and SMC differentiation. We found that mice with specific deletion of Smad4 in Tbx18-expressing ureteral mesenchyme exhibited hydroureter and hydronephrosis at embryonic day (E) 16.5, and the mutant mesenchymal cells failed to differentiate into SMCs with increased apoptosis and decreased proliferation. Molecular markers for SMCs including alpha smooth muscle actin (α-SMA) and smooth muscle myosin heavy chain (SM-MHC) were absent in the mutant ureters. Moreover, disruption of Smad4 significantly reduced the expression of genes, including Sox9, Tbx18 and Myocardin associated with SMC differentiation. These findings suggest that Smad4 is essential for initiating the SMC differentiation program during ureter development.     

植物体细胞胚同步化发生的控制

体细胞胚发生的不同步是植物胚状体发生过程中的问题之一。控制体细胞胚同步发生的方法主要有物理方法和化学方法,文章就此作简要介绍。     

The Endolysosomal System in Cell Death and Survival

The endocytic pathway is a system specialized for the uptake of compounds from the cell microenvironment for their degradation. It contains an arsenal of hydrolases, including proteases, which are normally enclosed in membrane-bound organelles, but if released to the cytosol can initiate apoptosis signaling pathways. Endogenous and exogenous compounds have been identified that can mediate destabilization of lysosomal membranes, and it was shown that lysosomal proteases are not only able to initiate apoptotic signaling but can also amplify the apoptotic pathways initiated in other cellular compartments. The endocytic pathway also receives cargo destined for degradation via the autophagic pathway. By recycling energy and biosynthetic substrates, and by degrading damaged organelles and molecules, the endocytic system assists the autophagic system in resisting apoptotic stimuli. Steps leading to lysosomal membrane permeabilization and subsequent triggering of cell death as well as the therapeutic potential of intervention in lysosomal membrane permeabilization will be discussed.Since the discovery of lysosomes in 1950s (de Duve et al. 1955), the concept of the endocytic pathway has changed. Although there has been huge progress in understanding the molecular mechanisms of targeting and fusion of organelles, several conceptual dilemmas have not been completely resolved. The primary function of the endocytic pathway is bulk degradation and recycling of the internalized material and redundant cellular components. Over the years, additional functions have been associated with it. Endosomes and lysosomes can fuse with the plasma membrane to repair it and to release the accumulated nondegradable material (Medina et al. 2011). Intraluminal vesicles are the source of exosomes, which have multiple functions, especially for the immune system (Ludwig and Giebel 2012). Endosomes have numerous functions in fighting infections: they can signal the presence of pathogens through Toll-like receptors, they are the site of antigenic peptide generation and their assembly with major histocompatibility complex class II molecules, and they can also kill residing pathogens (Gruenberg and van der Goot 2006). Because of a high content of proteases, de Duve (1959) coined the figurative term “suicide bags” for lysosomes, a concept since supported by a wealth of experimental reports (de Duve 1959). Perhaps the best examples of this concept are natural killer cells and cytotoxic T cells. Both have specialized lysosome-related organelles, secretory granules, that contain perforin and granzyme B, which can mediate apoptosis in the target cell (Blott and Griffiths 2002; Trapani and Smyth 2002). However, every cell can potentially become a victim of its own lysosomal hydrolases, especially if lysosomal membranes are destabilized so that the enzymes can escape into the cytosol. These offer great potential to exploit scenarios for therapy for certain diseases, most importantly cancer. On the other hand, by enabling degradation of the material sequestered by autophagy, the endocytic pathway can assist autophagy in counteracting apoptosis when cells are challenged with an apoptotic stimulus (Repnik and Turk 2010; Hafner Česen et al. 2012; Repnik et al. 2012).     

植物细胞编程性死亡的调控

细胞编程性死亡（PCD）在植物生长发育及植物对环境的适应性方面起重要作用。文章主要从PCD相关基因,信号转导途径,蛋白酶及核酸酶等方面介绍植物细胞编程性死亡的调控。     

Mitochondrial Peroxiredoxin 3 Regulates Sensory Cell Survival in the Cochlea

This study delineates the role of peroxiredoxin 3 (Prx3) in hair cell death induced by several etiologies of acquired hearing loss (noise trauma, aminoglycoside treatment, age). In vivo, Prx3 transiently increased in mouse cochlear hair cells after traumatic noise exposure, kanamycin treatment, or with progressing age before any cell loss occurred; when Prx3 declined, hair cell loss began. Maintenance of high Prx3 levels via treatment with the radical scavenger 2,3-dihydroxybenzoate prevented kanamycin-induced hair cell death. Conversely, reducing Prx3 levels with Prx3 siRNA increased the severity of noise-induced trauma. In mouse organ of Corti explants, reactive oxygen species and levels of Prx3 mRNA and protein increased concomitantly at early times of drug challenge. When Prx3 levels declined after prolonged treatment, hair cells began to die. The radical scavenger p-phenylenediamine maintained Prx3 levels and attenuated gentamicin-induced hair cell death. Our results suggest that Prx3 is up-regulated in response to oxidative stress and that maintenance of Prx3 levels in hair cells is a critical factor in their susceptibility to acquired hearing loss.     

Plant Proteases Involved in Regulated Cell Death

Each plant genome encodes hundreds of proteolytic enzymes. These enzymes can be divided into five distinct classes: cysteine-, serine-, aspartic-, threonine-, and metalloproteinases. Despite the differences in their structural properties and activities, members of all of these classes in plants are involved in the processes of regulated cell death–a basic feature of eukaryotic organisms. Regulated cell death in plants is an indispensable mechanism supporting plant development, survival, stress responses, and defense against pathogens. This review summarizes recent advances in studies of plant proteolytic enzymes functioning in the initiation and execution of distinct types of regulated cell death.     

线粒体在控制细胞死亡中的作用

细胞死亡由细胞坏死或细胞凋亡所致。细胞坏死时 ,细胞质膜形成疱 (突起 ) ,疱破裂释放细胞内容物 ;细胞凋亡时 ,细胞内容物不释放到细胞外。细胞坏死时 ,细胞内ＡＴＰ耗竭 ;凋亡时 ,细胞需利用ＡＴＰ完成凋亡过程。1.线粒体外膜释放凋亡活性物质细胞凋亡过程中 ,原先位于线粒体膜间隙的某些与凋亡有关的活性物质释放到胞液中 ,这些物质包括细胞色素ｃ(Ｃｙｔｃ)、凋亡诱导因子 (ａｐｏｐｔｏｓｉｓ ｉｎｄｕｃｉｎｇｆａｃｔｏｒ ,ＡＩＦ)、线粒体胱天蛋白酶 (ｃａｓｐａｓｅ)2 ,3,9、ｈｓｐ10、ｈｓｐ6 0、Ｂｃｌ 2家族成员等。细胞受到凋…     

植物衰老中的编程性细胞死亡

本文通过对植物衰老和动植物中编程性细胞死亡(PCD)的研究,阐述了植物衰老中PCD存在的依据,澄清了植物衰老和PCD的关系,提出了植物衰老中可能的PCD发生途径,为调控植物衰老的遗传操作提供依据.     

植物衰老中的编程性细胞死亡

本文通过对植物衰老和动植物中编程性细胞死亡(PCD)的研究,阐述了植物衰老中PCD存在的依据,澄清了植物衰老和PCD的关系,提出了植物衰老中可能的PCD发生途径,为调控植物衰老的遗传操作提供依据。