Stat3 Signaling Promotes Survival And Maintenance Of Medullary Thymic Epithelial Cells

Medullary thymic epithelial cells (mTECs) are essential for establishing central tolerance by expressing a diverse array of self-peptides that delete autoreactive thymocytes and/or divert thymocytes into the regulatory T cell lineage. Activation of the NFκB signaling pathway in mTEC precursors is indispensable for mTEC maturation and proliferation resulting in proper medullary region formation. Here we show that the Stat3-mediated signaling pathway also plays a key role in mTEC development and homeostasis. Expression of a constitutively active Stat3 transgene targeted to the mTEC compartment increases mTEC cellularity and bypasses the requirement for signals from positively selected thymocytes to drive medullary region formation. Conversely, conditional deletion of Stat3 disrupts medullary region architecture and reduces the number of mTECs. Stat3 signaling does not affect mTEC proliferation, but rather promotes survival of immature MHCII^loCD80^lo mTEC precursors. In contrast to striking alterations in the mTEC compartment, neither enforced expression nor deletion of Stat3 affects cTEC cellularity or organization. These results demonstrate that in addition to the NFkB pathway, Stat3-mediated signals play an essential role in regulating mTEC cellularity and medullary region homeostasis.     

5-Lipoxygenase as a drug target: A review on trends in inhibitors structural design,SAR and mechanism based approach

The most common inflammatory disease of the airways is asthma among children affecting around 235 million people worldwide. 5-Lipoxygenase (5-LOX) is a crucial enzyme which helps in the conversion of arachidonic acid (AA) to leukotrienes (LTs), the lipid mediators. It is associated with several inflammation related disorders such as asthma, allergy, and atherosclerosis. Therefore, it is considered as a promising target against inflammation and asthma. Currently, the only drug against 5-LOX which is available is Zileuton, while a few inhibitors are in clinical trial stages such as Atreleuton and Setileuton. So, there is a dire requirement in the area of progress of novel 5-LOX inhibitors which necessitates an understanding of their structure activity relationship and mode of action. In this review, novel 5-LOX inhibitors reported so far, their structural design, SAR and developmental strategies along with clinical updates are discussed over the last two decades.     

Molecular and functional analyses of a novel class I secretory nuclease from the human pathogen, Leishmania donovani

The primitive protozoan pathogen of humans, Leishmania donovani, resides and multiplies in highly restricted micro-environments within their hosts (i.e. as promastigotes in the gut lumen of their sandfly vectors and as amastigotes in the phagolysosomal compartments of infected mammalian macrophages). Like other trypanosomatid parasites, they are purine auxotrophs (i.e. lack the ability to synthesize purines de novo) and therefore are totally dependent upon salvaging these essential nutrients from their hosts. In that context, in this study we identified a unique 35-kDa, dithiothreitol-sensitive nuclease and showed that it was constitutively released/secreted by both promastigote and amastigote developmental forms of this parasite. By using several different molecular approaches, we identified and characterized the structure of LdNuc(s), a gene that encodes this new 35-kDa class I nuclease family member in these organisms. Homologous episomal expression of an epitope-tagged LdNuc(s) chimeric construct was used in conjunction with an anti-LdNuc(s) peptide antibody to delineate the functional and biochemical properties of this unique 35-kDa parasite released/secreted enzyme. Results of coupled immunoprecipitation-enzyme activity analyses demonstrated that this "secretory" enzyme could hydrolyze a variety of synthetic polynucleotides as well as several natural nucleic acid substrates, including RNA and single- and double-stranded DNA. Based on these cumulative observations, we hypothesize that within the micro-environments of its host, this leishmanial "secretory" nuclease could function at a distance away from the parasite to harness (i.e. hydrolyze/access) host-derived nucleic acids to satisfy the essential purine requirements of these organisms. Thus, this enzyme might play an important role(s) in facilitating the survival, growth, and development of this important human pathogen.     

Genetic engineering of indica rice with AtDREB1A gene for enhanced abiotic stress tolerance

Plant Cell, Tissue and Organ Culture (PCTOC) - Adventitious root (AR) culturing is an effective approach for obtaining bioactive compounds from the endangered plant species of Oplopanax elatus...     

Biological mechanisms of aging predict age‐related disease co‐occurrence in patients

Genetic, environmental, and pharmacological interventions into the aging process can confer resistance to multiple age‐related diseases in laboratory animals, including rhesus monkeys. These findings imply that individual mechanisms of aging might contribute to the co‐occurrence of age‐related diseases in humans and could be targeted to prevent these conditions simultaneously. To address this question, we text mined 917,645 literature abstracts followed by manual curation and found strong, non‐random associations between age‐related diseases and aging mechanisms in humans, confirmed by gene set enrichment analysis of GWAS data. Integration of these associations with clinical data from 3.01 million patients showed that age‐related diseases associated with each of five aging mechanisms were more likely than chance to be present together in patients. Genetic evidence revealed that innate and adaptive immunity, the intrinsic apoptotic signaling pathway and activity of the ERK1/2 pathway were associated with multiple aging mechanisms and diverse age‐related diseases. Mechanisms of aging hence contribute both together and individually to age‐related disease co‐occurrence in humans and could potentially be targeted accordingly to prevent multimorbidity.     

Ceramide Glycanase Activities in Human Cancer Cells

Ceramide glycanase (CGase) activities have been detected in different human tumor cells (colon, carcinoma Colo-205; neuroblastoma, IMR-32; breast cancer lines, SKBr3 and MCF7). However, the level of enzymatic activity is lower in these cells compared to that present in other mammalian tissues reported before (Basu, M., Kelly, P., Girzadas, M. A., Li, Z., and Basu, S. Methods Enzymol. (in press)). The majority of CGase activity was found in the 100,000g soluble supernatant fraction isolated from all these cell lines and tissues. Using the soluble enzyme, the requirement for optimum CGase activity was found to be consistent with previous observations found for rat and rabbit tissues (Basu, M., Dastgheib, S., Girzadas, M. A., O'Donnell, P. H., Westervelt, C. W., Li, Z., Inokuchi, J. I., and Basu, S. (1998) Acta Pol. Biochim. 42:327). The CGase activities from both Colo-205 and IMR-32 cells are optimum at a protein to detergent ratio of one. All the mammalian CGases, including human cancer cells, show an optimum pH between 5.5 and 5.8 in sodium acetate buffer. The CGase activities from cancer cells are found to be cation-independent; however, mercury, zinc, and copper ions seem to inhibit the enzyme activity substantially in both tumor cells lines. The mercury ion inhibition of CGase activities from all different sources indicates a possible structural homology in the CGase proteins.Radiolabeled substrates, labeled at the sphingosine double bond or at the 3-position of sphingosine without modifying double bond of sphingosine were used in this investigation. Both were active substrates with all enzyme preparations isolated from different cancer cells (apparent Km, 500 M for nLcOse5[³H-DT]Cer and 350 M for GgOse4[sph-3-³H]Cer with Colo-205 enzyme). Structural analogues of ceramide and sphingosine (L-PPMP, L-PDMP, alkylamines, and Tamoxifen) inhibited cancer cell CGase activities in vitro.     

Mechanism of loading the Escherichia coli DNA polymerase III beta sliding clamp on DNA. Bona fide primer/templates preferentially trigger the gamma complex to hydrolyze ATP and load the clamp

The Escherichia coli DNA polymerase III gamma complex clamp loader assembles the ring-shaped beta sliding clamp onto DNA. The core polymerase is tethered to the template by beta, enabling processive replication of the genome. Here we investigate the DNA substrate specificity of the clamp-loading reaction by measuring the pre-steady-state kinetics of DNA binding and ATP hydrolysis using elongation-proficient and deficient primer/template DNA. The ATP-bound clamp loader binds both elongation-proficient and deficient DNA substrates either in the presence or absence of beta. However, elongation-proficient DNA preferentially triggers gamma complex to release beta onto DNA with concomitant hydrolysis of ATP. Binding to elongation-proficient DNA converts the gamma complex from a high affinity ATP-bound state to an ADP-bound state having a 10(5)-fold lower affinity for DNA. Steady-state binding assays are misleading, suggesting that gamma complex binds much more avidly to non-extendable primer/template DNA because recycling to the high affinity binding state is rate-limiting. Pre-steady-state rotational anisotropy data reveal a dynamic association-dissociation of gamma complex with extendable primer/templates leading to the diametrically opposite conclusion. The strongly favored dynamic recognition of extendable DNA does not require the presence of beta. Thus, the gamma complex uses ATP binding and hydrolysis as a mechanism for modulating its interaction with DNA in which the ATP-bound form binds with high affinity to DNA but elongation-proficient DNA substrates preferentially trigger hydrolysis of ATP and conversion to a low affinity state.