The membrane and lipids as integral participants in signal transduction: lipid signal transduction for the non-lipid biochemist

Reviews of signal transduction have often focused on the cascades of protein kinases and protein phosphatases and their cytoplasmic substrates that become activated in response to extracellular signals. Lipids, lipid kinases, and lipid phosphatases have not received the same amount of attention as proteins in studies of signal transduction. However, lipids serve a variety of roles in signal transduction. They act as ligands that activate signal transduction pathways as well as mediators of signaling pathways, and lipids are the substrates of lipid kinases and lipid phosphatases. Cell membranes are the source of the lipids involved in signal transduction, but membranes also constitute lipid barriers that must be traversed by signal transduction pathways. The purpose of this review is to explore the magnitude and diversity of the roles of the cell membrane and lipids in signal transduction and to highlight the interrelatedness of families of lipid mediators in signal transduction.     

Differential effects of murine and human factor X on adenovirus transduction via cell-surface heparan sulfate

Serum coagulation factor X (FX) is proposed to play a major role in adenovirus tropism, promoting transduction by bridging the virus to cell-surface heparan sulfate proteoglycans (HSPGs). Both murine FX and human FX increased transduction by Ad.CMVfLuc, an adenovirus vector, in murine hepatocyte-like cells and human hepatocarcinoma cells. In contrast, only hFX increased transduction of several non-hepatic cancer cell lines and Chinese hamster ovary (CHO) cells. Not only was mFX unable to promote transduction in these cells, it competitively blocked hFX-enhanced transduction. Competition and HSPG digestion experiments suggested mFX- and hFX-enhanced transduction in hepatocyte-derived cells, and hFX-enhanced transduction in epithelial cancer cells were dependent on HSPGs. Ad·hFX-mediated transduction of CHO mutants unable to produce HSPGs was also curtailed. Hepatocyte-derived cells expressed substantially more HSPGs than the cancer cell lines. Dose-response curves and heparin-Sepharose binding suggested Ad·hFX has greater affinity for HSPGs than does Ad·mFX. In coagulation factor-depleted mice hFX also had enhanced ability, compared with mFX, to reconstitute hepatic adenovirus transduction. The results suggest that differences in Ad·hFX and Ad·mFX affinity to HSPGs may result in differences in their ability to enhance adenovirus transduction of many cells. These findings may have implications for murine models of adenovirus vector targeting.     

Frequency of F116-mediated transduction of Pseudomonas aeruginosa in a freshwater environment.

Transduction of Pseudomonas aeruginosa streptomycin resistance by a generalized transducing phage, F116, was shown to occur during a 10-day incubation in a flow-through environmental test chamber suspended in a freshwater reservoir. Mean F116 transduction frequencies ranged from 1.4 X 10(-5) to 8.3 X 10(-2) transductants per recipient during the in situ incubation. These transduction frequencies were comparable to transduction frequencies determined in preliminary laboratory transduction experiments. The results demonstrate the potential for naturally occurring transduction in aquatic environments and concurrent environmental and ecological ramifications.     

Transduction of Gal+ by Coliphage T1 I. Role of Hybrids of Bacterial and Prophage λ Deoxyribonucleic Acid

Hybrids of lambda and adjacent bacterial deoxyribonucleic acid carried in T1 particles were able to transduce Gal(+) with a greatly increased efficiency to strains which were not immune to lambda compared to immune strains. The enhanced transduction was dependent on a functional recA(+) gene in the recipient. Mutations of the donor's lambda prophage which abolished the function of either the cI, O, or P genes in the recipients led to a further enhancement of transduction. The rate of transduction of a nonlysogenic recipient such as W3350 by the hybrid particles may be as much as 140 times greater than transduction of the lysogenic recipient W3350(lambda). In addition to the effect of lambda immunity in blocking enhanced transduction, mutations of the N gene of the donor's lambda prophage abolished enhanced transduction. Mutations in the red, int, xis, and Q genes of the donor's prophage had no significant effect on transduction. The hybrids which mediated the enhanced transduction are called (lambda-gal)T1.     

Frequency of F116-mediated transduction of Pseudomonas aeruginosa in a freshwater environment.

Transduction of Pseudomonas aeruginosa streptomycin resistance by a generalized transducing phage, F116, was shown to occur during a 10-day incubation in a flow-through environmental test chamber suspended in a freshwater reservoir. Mean F116 transduction frequencies ranged from 1.4 X 10(-5) to 8.3 X 10(-2) transductants per recipient during the in situ incubation. These transduction frequencies were comparable to transduction frequencies determined in preliminary laboratory transduction experiments. The results demonstrate the potential for naturally occurring transduction in aquatic environments and concurrent environmental and ecological ramifications.     

Gangliosides are essential for bovine adeno-associated virus entry

Recombinant adeno-associated viruses (AAV) are promising gene therapy vectors. We have recently identified a bovine adeno-associated virus (BAAV) that demonstrates unique tropism and transduction activity compared to primate AAVs. To better understand the entry pathway and cell tropism of BAAV, we have characterized the initial cell surface interactions required for transduction with BAAV vectors. Like a number of AAVs, BAAV requires cell surface sialic acid groups for transduction and virus attachment. However, glycosphingolipids (GSLs), not cell surface proteins, were required for vector entry and transduction. Incorporation of gangliosides, ceramide-based glycolipids containing one or more sialic acid groups, into the cytoplasmic cell membranes of GSL-depleted COS cells partially reconstituted BAAV transduction. The dependency of BAAV on gangliosides for transduction was further confirmed by studies with C6 cells, a rat glioma cell line that is deficient in the synthesis of complex gangliosides. C6 cells were resistant to transduction by BAAV. Addition of gangliosides to C6 cells prior to transduction rendered the cells susceptible to transduction by BAAV. Therefore, gangliosides are a likely receptor for BAAV.     

Eph-ephrin介导反向信号传递的研究进展

双向信号传递是细胞间通讯领域中新近阐明的机制,酪氨酸激酶受体-配体(Eph-ephrin)介导的双向信号传递是此机制中的一个重要代表.Eph酪氨酸激酶家族受体及其配体ephrin家族成员是在神经发育、血管新生等方面起重要作用的分子,通过Eph向细胞内传递的信号称为正向信号,通过其配体ephrin的信号称为反向信号.Ephrin家族又可根据分子结构分为2个亚家族,其中ephrinB为跨膜蛋白,可通过酪氨酸磷酸化依赖和PDZ结合结构域介导2种方式向胞内传递反向信号,活化FAK、JNK、Wnt等信号通路,ephrinA为糖基磷脂酰肌醇锚定蛋白,也具有反向信号传递功能.     

Small increases in pH enhance retroviral vector transduction efficiency of NIH-3T3 cells

Increases in pH between 7.1 and 7.7 increase the efficiency of polybrene (Pb)- and protamine sulfate (PS)-aided retroviral transduction of NIH-3T3 cells in a serum-lot-dependent manner. The increase in Pb-aided transduction efficiency at pH 7.7, relative to the value at pH 7.33, ranged from 13% to 49% for three serum lots. For a constant Moloney murine leukemia virus (MMLV) vector dilution at pH 7.33, three different serum lots resulted in absolute transduction efficiencies ranging from 29% to 53% using Pb. At the same vector dilution, PS-aided transduction was less effective on an absolute basis than Pb-aided transduction, but the benefit of elevated pH was more pronounced with PS. There was a similar enhancement with PS at elevated pH for a murine stem cell virus (MSCV) vector as for the MMLV vector. The benefit at pH 7.7 for PS-aided transduction was partially due to greater PS stability at elevated pH. Heat inactivating the serum supplement or adding protease inhibitors helped to stabilize PS. This increased the absolute transduction efficiency but decreased the relative benefit of elevated pH to a level similar to that for Pb-aided transduction. Incubating Pb with the vector at pH 7.1 for 10 min, prior to readjusting to pH 7.7 and transducing the cells, was sufficient to abrogate the beneficial effects of transduction at pH 7.7. In contrast, prior exposure of PS with vector at pH 7.1 did not affect subsequent transduction at pH 7.7. These results indicate that pH is an important variable in retroviral transduction and that the relative benefits of Pb or PS on retroviral vector transduction will vary with the pH, polymer addition method, and serum lot.     

Transduction transmission of the extrachromosomal markers of antibiotic resistance in staphylococcal populations]

Transduction of extrachromosomal markers of resistance to penicillin and erythromycin in staphylococcal strains isolated from patients was studied. Two transduction methods were compared, i. e. transduction with a phage filtrate of the donor culture resistant to erythromycin and transduction on mixed cultivation of the donor and recipient. A higher transduction rate was observed with the latter method. Mixed cultivation of the donor cultures resistant to penicillin or erythromycin and the recipient strains of the wild type sensitive to these antibiotic resulted in transduction of the respective markers. Transductants which acquired prophage 6 simultaneously with marker Egg became donors of erythromycin resistance.     

胰岛素信号转导障碍与胰岛素抵抗的形成

胰岛素生理作用的发挥,起始于胰岛素与其受体的结合,并由此引起细胞内一系列信号转导,最终到达各效应器产生各种生理效应。胰岛素信号转导在胰岛素生理作用的发挥中起着至关重要的作用。胰岛素信号转导减弱或受阻,使得胰岛素生理作用减弱,导致胰岛素抵抗形成。本文综述了胰岛素信号转导失调在胰岛素抵抗形成中的作用。     

植物对盐胁迫响应的信号转导途径

植物通过调控复杂的信号网络来应对盐胁迫。近年来,随着植物基因工程技术的发展,对植物在盐胁迫下信号转导系统的研究取得了一定进展。本文以拟南芥为代表,对盐胁迫下参与调控植物耐盐生理响应的两大类主要信号转导途径——Ca2＋依赖型信号转导通路和丝裂原活化蛋白激酶（MAPK）级联反应途径的研究进展进行综述,主要介绍参与各信号转导通路的组件及诱发的耐盐生理响应等方面,并对该研究领域存在的问题及今后可能的研究方向进行展望。     

Distinct classes of proteasome-modulating agents cooperatively augment recombinant adeno-associated virus type 2 and type 5-mediated transduction from the apical surfaces of human airway epithelia

Tripeptidyl aldehyde proteasome inhibitors have been shown to effectively increase viral capsid ubiquitination and transduction of recombinant adeno-associated virus type 2 (rAAV-2) and rAAV-5 serotypes. In the present study we have characterized a second class of proteasome-modulating agents (anthracycline derivatives) for their ability to induce rAAV transduction. The anthracycline derivatives doxorubicin and aclarubicin were chosen for analysis because they have been shown to interact with the proteasome through a mechanism distinct from that of tripeptidyl aldehydes. Our studies demonstrated that doxorubicin and aclarubicin also significantly augmented rAAV transduction in airway cell lines, polarized human airway epithelia, and mouse lungs. Both tripeptidyl aldehyde and anthracycline proteasome-modulating agents similarly augmented nuclear accumulation of rAAV in A549 and IB3 airway cell lines. However, these two cell types demonstrated cell specificity in the ability of N-acetyl-L-leucyl-L-leucyl-L-norleucine (LLnL) or doxorubicin to augment rAAV transduction. Interestingly, the combined administration of LLnL and doxorubicin resulted in substantially increased transduction (>2,000-fold) following apical infection of human polarized epithelia with either rAAV-2 or rAAV-5. In summary, the cell type specificity of LLnL and doxorubicin to induce rAAV transduction, together with the ability of these compounds to synergistically enhance rAAV transduction in polarized airway epithelial induction, suggests that these two classes of compounds likely modulate different proteasome functions that affect rAAV transduction. Findings from this study provide new insights into how modulation of proteasome function can be effectively used to augment rAAV transduction in airway epithelia for gene therapy of cystic fibrosis.     

丙型肝炎病毒蛋白作用于细胞信号转导途径的研究进展

细胞信号转导异常往往与人类疾病的发生、发展密切相关。一些病毒致病和感染机制即为病毒抗原蛋白作用宿主细胞信号转导途径,导致宿主细胞内信号转导发生紊乱。丙型肝炎病毒（HCV）是引发慢性丙型肝炎,导致肝硬化和肝细胞癌发生的主要病原体,但目前HCV的致病机制与宿主内持续感染机制尚不清楚。HCV致病机制可能与HCV表达的蛋白质干扰宿主细胞信号转导途径而导致异常的细胞信号转导有关。研究HCV蛋白对宿主细胞信号转导途径的影响不仅有助于阐明其致病机制,还能为新药设计和寻找新的治疗方法提供新思路和新靶点。本文主要综述了近年来国内外有关HCV蛋白作用细胞信号转导途径的研究进展。     

Rate limiting factors for DNA transduction induced by weak electromagnetic field

DNA transduction across aqueous solutions has been reported previously. In this study, we examined a few key factors affecting DNA transduction rate in an extremely low frequency electromagnetic field. These include: the chemical composition of the aqueous solutions, the type of experimental vessel, the dilution step, and the origin of the DNA fragments. The results indicate that partially introducing essential ingredients for DNA amplification (i.e. dNTPs and PCR buffer) to the aqueous solution enhanced the transduction rate greatly, and transduction vessels made of hydrophilic quartz yielded more favorable results than vessels made of hydrophobic plastic. In addition, performing a serial dilution to the transduction solution more than doubled the transduction rate compared to that without the dilution step. For the DNA fragments used in this study, there was one with a pathogenic origin and two with non-pathogenic origins. However, all three fragments achieved DNA transduction regardless of the difference in their origins. The experimental setup for eliminating the false positives caused by both biological and potentially physical contamination is also described.     

Role of the JAK/STAT signal transduction pathway in the regulation of gene expression in CNS

Over the last 20 years the JAK/STAT signal transduction pathway has been extensively studied. An enormous amount of data on different cell signal transduction pathways is now available. The JAK/STAT signal transduction pathway is one of the intracellular signaling pathways activated by cytokines and growth factors that was first studied in the hematopoietic system, but recent data demonstrate that this signal transduction is also greatly utilized by other systems. The JAK/STAT pathway is a signaling cascade that links the activation of specific cell membrane receptors to nuclear gene expression. This review is focused on the role of JAK/STAT signal transduction pathway activation in the central nervous system (CNS).     

Optimization of the Transductional Efficiency of Lentiviral Vectors: Effect of Sera and Polycations

Lentiviral vectors are widely used as effective gene-delivery vehicles. Optimization of the conditions for efficient lentiviral transduction is of a high importance for a variety of research applications. Presence of positively charged polycations reduces the electrostatic repulsion forces between a negatively charged cell and an approaching enveloped lentiviral particle resulting in an increase in the transduction efficiency. Although a variety of polycations are commonly used to enhance the transduction with retroviruses, the relative effect of various types of polycations on the efficiency of transduction and on the potential bias in the determination of titer of lentiviral vectors is not fully understood. Here, we present data suggesting that DEAE-dextran provides superior results in enhancing lentiviral transduction of most tested cell lines and primary cell cultures. Specific type and source of serum affects the efficiency of transduction of target cell populations. Non-specific binding of enhanced green fluorescent protein (EGFP)-containing membrane aggregates in the presence of DEAE-dextran does not significantly affect the determination of the titer of EGFP-expressing lentiviral vectors. In conclusion, various polycations and types of sera should be tested when optimizing lentiviral transduction of target cell populations.     

Adeno-Associated Virus Type 6 (AAV6) Vectors Mediate Efficient Transduction of Airway Epithelial Cells in Mouse Lungs Compared to That of AAV2 Vectors

Although vectors derived from adeno-associated virus type 2 (AAV2) promote gene transfer and expression in many somatic tissues, studies with animal models and cultured cells show that the apical surface of airway epithelia is resistant to transduction by AAV2 vectors. Approaches to increase transduction rates include increasing the amount of vector and perturbing the integrity of the epithelia. In this study, we explored the use of vectors based on AAV6 to increase transduction rates in airways. AAV vectors were made using combinations of rep, cap, and packaged genomes from AAV2 or AAV6. The packaged genomes encoded human placental alkaline phosphatase and contained terminal repeat sequences from AAV2 or AAV6. We found that transduction efficiency was primarily dependent on the source of Cap protein, defined here as the vector pseudotype. The AAV6 and AAV2 pseudotype vectors exhibited different tropisms in tissue-cultured cells, and cell transduction by AAV6 vectors was not inhibited by heparin, nor did they compete for entry in a transduction assay, indicating that AAV6 and AAV2 capsid bind different receptors. In vivo analysis of vectors showed that AAV2 pseudotype vectors gave high transduction rates in alveolar cells but much lower rates in the airway epithelium. In contrast, the AAV6 pseudotype vectors exhibited much more efficient transduction of epithelial cells in large and small airways, showing up to 80% transduction in some airways. These results, combined with our previous results showing lower immunogenicity of AAV6 than of AAV2 vectors, indicate that AAV6 vectors may provide significant advantages over AAV2 for gene therapy of lung diseases like cystic fibrosis.     

G蛋白及其在细胞信号转导中的作用

概述G蛋白的结构、种类、转导信息的机制,细菌毒素对G蛋白调节的影响及研究G蛋的意义和今后发展的重点。     

植物抗逆相关蛋白激酶的结构与功能

植物在遭受外界逆境胁迫时,体内的信号传导系统能够感知、传递逆境胁迫信号,并引起各种生理生化反应以适应环境。植物蛋白激酶在信号感知、传导以及基因的表达调控中起重要的作用。蛋白激酶在信号传导过程的功能是磷酸化修饰目的蛋白,而磷酸化的实现需要蛋白质之间相互作用。本文从植物蛋白激酶的结构、分类、与激素信号传导之间的关系等方面进行了系统的阐述,对蛋白激酶介导的植物抗性与发育的最新研究进展进行了系统的总结,为解析蛋白激酶在植物生长发育中的抗逆机理提供依据。