Regulation of apoptotic signal transduction pathways by the heat shock proteins

The study about apoptotic signal transductions has become a project to reveal the molecular mechanisms of apoptosis. Heat shock proteins (hsps), which play an important role in cell growth and apoptosis, have attracted great attentions. A lot of researches have showed there is a hsps superfamily including hsp90, hsp70, hsp60 and hsp27, etc., which regulates the biological behaviors of cells, particularly apoptotic signal transduction in Fas pathway, JNK/SAPK pathway and caspases pathway at different levels, partly by the function of molecular chaperone.     

木聚糖酶基因研究进展

半纤维素分解微生物在自然界碳素循环中起着重要作用,半纤维素是植物多糖的重要成分之一。木聚糖则是半纤维素的主要成分。木聚糖酶(EC3.2.1.8)可催化木聚糖的水解,在各种各样的生物体里都发现有木聚糖酶,如细菌、放线菌、真菌。在过去几十年里,有超过100个木聚糖酶基因被克隆进同源或异源宿主中,其目的是为了超表达木聚糖酶和改变它们的特性以适应商业应用。木聚糖酶的应用极其广泛,可用于生物转化、造纸、食品、饲料、能源、纺织等行业。尤其是迫切的环境问题将进一步促进木聚糖酶研究的开展。     

Application of repeated aspartate tags to improving extracellular production of Escherichia coli l-asparaginase isozyme II

Asparaginase isozyme II from Escherichia coli is a popular enzyme that has been used as a therapeutic agent against acute lymphoblastic leukemia. Here, fusion tag systems consisting of the pelB signal sequence and various lengths of repeated aspartate tags were devised to highly express and to release active asparaginase isozyme II extracellularly in E. coli. Among several constructs, recombinant asparaginase isozyme II fused with the pelB signal sequence and five aspartate tag was secreted efficiently into culture medium at 34.6 U/mg cell of specific activity. By batch fermentation, recombinant E. coli produced 40.8 U/ml asparaginase isozyme II in the medium. In addition, deletion of the gspDE gene reduced extracellular production of asparaginase isozyme II, indicating that secretion of recombinant asparaginase isozyme II was partially ascribed to the recognition by the general secretion machinery. This tag system composed of the pelB signal peptide, and repeated aspartates can be applied to extracellular production of other recombinant proteins.     

Regionally diverse mitochondrial calcium signaling regulates spontaneous pacing in developing cardiomyocytes

The quintessential property of developing cardiomyocytes is their ability to beat spontaneously. The mechanisms underlying spontaneous beating in developing cardiomyocytes are thought to resemble those of adult heart, but have not been directly tested. Contributions of sarcoplasmic and mitochondrial Ca²⁺-signaling vs. I_f-channel in initiating spontaneous beating were tested in human induced Pluripotent Stem cell-derived cardiomyocytes (hiPS-CM) and rat Neonatal cardiomyocytes (rN-CM). Whole-cell and perforated-patch voltage-clamping and 2-D confocal imaging showed: (1) both cell types beat spontaneously (60–140/min, at 24 °C); (2) holding potentials between −70 and 0 mV had no significant effects on spontaneous pacing, but suppressed action potential formation; (3) spontaneous pacing at −50 mV activated cytosolic Ca²⁺-transients, accompanied by in-phase inward current oscillations that were suppressed by Na⁺-Ca²⁺-exchanger (NCX)- and ryanodine receptor (RyR2)-blockers, but not by Ca²⁺- and I_f-channels blockers; (4) spreading fluorescence images of cytosolic Ca²⁺-transients emanated repeatedly from preferred central cellular locations during spontaneous beating; (5) mitochondrial un-coupler, FCCP at non-depolarizing concentrations (∼50 nM), reversibly suppressed spontaneous pacing; (6) genetically encoded mitochondrial Ca²⁺-biosensor (mitycam-E31Q) detected regionally diverse, and FCCP-sensitive mitochondrial Ca²⁺-uptake and release signals activating during I_NCX oscillations; (7) I_f-channel was absent in rN-CM, but activated only negative to −80 mV in hiPS-CM; nevertheless blockers of I_f-channel failed to alter spontaneous pacing.     

The synthetic precursor specific region of pre-pro-parathyroid hormone forms ion channels in lipid bilayers

We have used the chemically synthesized sequence of pre-pro-parathyroid hormone and several of its analogues to test the notion that the capacity of amphipathic peptides to aggregate in membranes and form ion-permeable channels correlates with their ability to function as signal sequences for secreted proteins. We found that pre-pro-parathyroid hormone (the signal sequence and pro-region of parathyroid hormone (M)), as well as some of its analogues, forms aggregates of monomers which are ion-permeable. The ion-permeable aggregates (2–3 monomers) formed by (M) are voltage-dependent and are more permeable for cations than for anions. The compounds which formed ion channels in bilayers also acted as potential signal sequences. We conclude that the ability of peptides to form ion-permeable pathways in bilayers may be correlated to their ability to function as signal peptides.     

丝状真菌细胞凋亡研究进展

细胞凋亡是真核生物中保守而重要的细胞死亡机制,与癌症、艾滋病等多种疾病密切相关.与酵母菌这一细胞凋亡模式生物相比,丝状真菌凋亡研究起步较晚但具有其独特的优势.近年来丝状真菌细胞凋亡的内外源诱因、细胞凋亡的特征以及信号传导通路等方面的研究进展迅速.丝状真菌,尤其是构巢曲霉和烟曲霉有望成为细胞凋亡研究新的模式物种.此外,研究丝状真菌细胞凋亡现象在农业和医疗领域也具有重要的应用价值,可为生物防治和人类真菌病的治疗提供新的思路.工业丝状真菌细胞凋亡研究有助于构建性状更加优良的工程菌株.     

尼古丁调控细胞凋亡的分子机制

尼古丁是烟草中生物碱的主要成分,其生物学作用广泛。尼古丁参与影响神经系统、呼吸系统和心血管系统等重要器官的发育,并与癌症的发生有着密切的关系。尼古丁通过对细胞凋亡的调控,发挥其生物学作用。现对尼古丁调控细胞凋亡相关的各种信号通路及其分子机制进行综述。     

植物细胞中的前纤维蛋白

肌动蛋白组成的微丝骨架是真核细胞中的重要结构,在体内处于高度动态变化之中,受多种肌动蛋白结合蛋白（actin-binding proteins）的调节。前纤维蛋白（profilin）是一种单体肌动蛋白结合蛋白,存在于所有的真核细胞中,在植物细胞中也得到较多的研究。前纤维蛋白除可以结合单体肌动蛋白之外,还可以与磷脂酰肌醇及富含多聚脯氨酸的蛋白质等多种分子结合,在细胞信号转导中行使着重要的功能。本文结合本实验室的研究结果,概述了前纤维蛋白的最新研究进展。     

A quantitative model for linking Na+/Ca2+ exchanger to SERCA during refilling of the sarcoplasmic reticulum to sustain [Ca2+] oscillations in vascular smooth muscle

We have developed a quantitative model for the creation of cytoplasmic Ca²⁺ gradients near the inner surface of the plasma membrane (PM). In particular we simulated the refilling of the sarcoplasmic reticulum (SR) via PM–SR junctions during asynchronous [Ca²⁺]_i oscillations in smooth muscle cells of the rabbit inferior vena cava. We have combined confocal microscopy data on the [Ca²⁺]_i oscillations, force transduction data from cell contraction studies and electron microscopic images to build a basis for computational simulations that model the transport of calcium ions from Na⁺/Ca²⁺ exchangers (NCX) on the PM to sarcoplasmic/endoplasmic reticulum Ca²⁺ ATPase (SERCA) pumps on the SR as a three-dimensional random walk through the PM–SR junctional cytoplasmic spaces. Electron microscopic ultrastructural images of the smooth muscle cells were elaborated with software algorithms to produce a very clear and dimensionally accurate picture of the PM–SR junctions. From this study, we conclude that it is plausible and possible for enough Ca²⁺ to pass through the PM–SR junctions to replete the SR during the regenerative Ca²⁺ release, which underlies agonist induced asynchronous Ca²⁺ oscillations in vascular smooth muscle.