Mechanisms of type-I interferon signal transduction

Interferons regulate a number of biological functions including control of cell proliferation, generation of antiviral activities and immumodulation in human cells. Studies by several investigators have identified a number of cellular signaling cascades that are activated during engagement of interferon receptors. The activation of multiple signaling cascades by the interferon receptors appears to be critical for the generation of interferon-mediated biological functions and immune surveillance. The present review summarizes the existing knowledge on the multiple signaling cascades activated by Type I interferons. Recent developments in this research area are emphasized and the implications of these new discoveries on our understanding of interferon actions are discussed.     

Sign-reversal during persistent activation in mu-opioid signal transduction

A concept of signal transduction in biological systems specifies that any instantaneous input is appreciated by its departure from the moving average of past activity. The concept provides an adequate account of the occurrence of both the one-directional (e.g. analgesic) effects induced by opioid receptor activation, and of the contra-directional (e.g. hyperalgesic) effects that can be observed when activation is discontinued. Following this transduction concept, the numerical simulations reported here revealed, remarkably, that under some parametric conditions, the input's effect may reverse even as input is maintained at a constant magnitude. In in vitro conditions that are proximal to the signal transduction that occurs when an opioid agonist binds to the G-protein coupled opioid receptor, the effects of opioid receptor activation were monitored by measuring time-dependent Ca(2+) responses in CHO-K1 cells transfected with a mu-opioid receptor and G(alpha 15) protein. The results indicate morphine to produce an initial increase in intracellular Ca(2+) concentration followed by a decrease below basal level. The occurrence of a sign-reversal was confirmed in native conditions of receptor-to-G protein coupling; the continuous in vivo infusion over a 2-week period of 0.31 mg rat(-1)day(-1) of fentanyl initially caused an increase of the mechanical threshold to induce a pain response (i.e. analgesia) that was followed by a decrease (i.e. hyperalgesia). The findings indicate that with opioid signaling systems, transduction mechanisms operate that may cause the sign of the effect to reverse not only when activation is discontinued but also whilst it is maintained at a constant magnitude.     

Mullerian inhibiting substance promotes interferon gamma-induced gene expression and apoptosis in breast cancer cells

This report demonstrates that in addition to interferons and cytokines, members of the TGF beta superfamily such as Mullerian inhibiting substance (MIS) and activin A also regulate IRF-1 expression. MIS induced IRF-1 expression in the mammary glands of mice in vivo and in breast cancer cells in vitro and stimulation of IRF-1 by MIS was dependent on activation of the NF kappa B pathway. In the rat mammary gland, IRF-1 expression gradually decreased during pregnancy and lactation but increased at involution. In breast cancer, the IRF-1 protein was absent in 13% of tumors tested compared with matched normal glands. Consistent with its growth suppressive activity, expression of IRF-1 in breast cancer cells induced apoptosis. Treatment of breast cancer cells with MIS and interferon gamma (IFN-gamma) co-stimulated IRF-1 and CEACAM1 expression and synergistic induction of CEACAM1 by a combination of MIS and IFN-gamma was impaired by antisense IRF-1 expression. Furthermore, a combination of IFN-gamma and MIS inhibited the growth of breast cancer cells to a greater extent than either one alone. Both reagents alone significantly decreased the fraction of cells in the S-phase of the cell cycle, an effect not enhanced when they were used in combination. However, MIS promoted IFN-gamma-induced apoptosis demonstrating a functional interaction between these two classes of signaling molecules in regulation of breast cancer cell growth.     

The genes of plant signal transduction

Due to the enormous importance of plants as a source of both food and raw materials, an understanding of the control of their growth and development is imperative. Basic to this understanding is the identification of the genes that enable the plant to adapt to its environment while at the same time adhering to its basic developmental plan. The aims of this review are first to briefly summarize the various approaches that have been used to identify these plant signaling genes and second to give an overview of the genes that have been cloned so far and what these genes may tell us about the nature of signal transduction in plants.

The advent of modern molecular biology and molecular genetics has revolutionized our ability to unravel the complexities of plant signal transduction pathways. A whole battery of techniques are now available to identify the genes that control the plants development and ability to adapt to its environment.⁶⁵ Each technique has its own strengths and weaknesses and must be carefully selected by the researcher according to the question that he or she would like to ask.     

Differential expression of imprinted genes in normal and IUGR human placentas

Genomic imprinting refers to silencing of one parental allele in the zygotes of gametes depending upon the parent of origin. Loss of imprinting (LOI) is the gain of function from the silent allele that can have a maximum effect of doubling the gene dosage. LOI may play a significant role in the etiology of intrauterine growth restriction (IUGR). Using placental tissue from 10 normal and 7 IUGR pregnancies, we conducted a systematic survey of the expression of a panel of 74 “putatively” imprinted genes using quantitative RT-PCR. We found that 52/74 (~70%) of the genes were expressed in human placentas. Nine of the 52 (17%) expressed genes were significantly differentially expressed between normal and IUGR placentas; 5 were up-regulated (PHLDA2, ILK2, NNAT, CCDC86, PEG10) and 4 down-regulated (PLAGL1, DHCR24, ZNF331, CDKAL1). We also assessed LOI profile of 14 imprinted genes in 14 normal and 24 IUGR placentas using a functional and sensitive assay developed in our laboratory. Little LOI was observed in any placentas for 5 of the genes (PEG10, PHLDA2, MEG3, EPS15, CD44). With the 149 heterozygosities examined, 40 (26.8%) exhibited LOI > 3%. Some genes exhibited frequent LOI in placentas regardless of the disease status (IGF2, TP73, MEST, SLC22A18, PEG3), while others exhibited LOI only in IUGR placentas (PLAGL1, DLK1, H19, SNRPN). Importantly, there was no correlation between gene expression and LOI profile. Our study suggests that genomic imprinting may play a role in IUGR pathogenesis, but mechanisms other than LOI may contribute to dysregulation of imprinted genes.     

肺炎嗜衣原体蛋白酶样活性因子免疫优势区基因 重组蛋白在早期诊断中的应用

[目的]克隆和表达肺炎嗜衣原体(Chlamydophila pneumoniae,Cpn)蛋白酶样活性因子(CPAF)免疫优势区基因,评价重组蛋白在早期感染诊断中的应用价值.[方法]挑选并克隆出Cpn CPAF免疫优势区基因,构建原核表达载体,诱导表达并纯化重组蛋白,分析其抗原特异性;间接ELISA法检测Cpn参考血清、临床血清标本中的特异性IgM抗体,以及呼吸道感染患者痰咽拭子中的Cpn抗原;检测沙眼衣原体(Chlamydia trachomatis,Ct)临床阳性血清和泌尿生殖道分泌物.[结果]高效表达和纯化出一相对分子量约51.3kDa的重组蛋白;Western blot证明其只与人抗Cpn抗血清发生特异性反应;间接ELISA法检测40份Cpn IgM参考血清,阴性和阳性结果的一致率均为100%(40/40);与"金标准"方法MIF对照,检测300例临床血清标本中的IgM抗体,符合率为98.3%;与PCR试剂对照,检测120份呼吸道感染患者痰咽拭子中的Cpn抗原,符合率为88.3%;检测Ct阳性血清和泌尿生殖道分泌物,与Ct没有交叉反应.[结论]制备的CPAF免疫优势区基因重组蛋白具有良好的抗原性,在Cpn感染早期诊断中具有较高的利用价值.     

A genomic analysis of two-component signal transduction in Streptococcus pneumoniae

A genomics-based approach was used to identify the entire gene complement of putative two-component signal transduction systems (TCSTSs) in Streptococcus pneumoniae. A total of 14 open reading frames (ORFs) were identified as putative response regulators, 13 of which were adjacent to genes encoding probable histidine kinases. Both the histidine kinase and response regulator proteins were categorized into subfamilies on the basis of phylogeny. Through a systematic programme of mutagenesis, the importance of each novel TCSTS was determined with respect to viability and pathogenicity. One TCSTS was identified that was essential for the growth of S. pneumoniaeThis locus was highly homologous to the yycFG gene pair encoding the essential response regulator/histidine kinase proteins identified in Bacillus subtilis and Staphylococcus aureus. Separate deletions of eight other loci led in each case to a dramatic attenuation of growth in a mouse respiratory tract infection model, suggesting that these signal transduction systems are important for the in vivo adaptation and pathogenesis of S. pneumoniae. The identification of conserved TCSTSs important for both pathogenicity and viability in a Gram-positive pathogen highlights the potential of two-component signal transduction as a multicomponent target for antibacterial drug discovery.