Astrocytic Expressions of Phosphorylated Akt,GSK3β and CREB Following an Excitotoxic Lesion in the Mouse Hippocampus

Glycogen synthase kinase 3β (GSK3β) is believed to play important roles in the regulation of synaptic plasticity, cell survival and circadian rhythms in the mature CNS. However, although several studies have been focused on the GSK3β, little is known about GSK3β changes in glial cells under neuropathological conditions. In this study, we evaluated the expressions of molecules associated with the GSK3β signaling pathway, following the induction of an excitotoxic lesion in mouse brain by kainic acid (KA) injection, which caused pyramidal cell degeneration in the hippocampal CA3 region. In injured hippocampi, Ser47-Akt (protein kinase B, PKB) phosphorylation increased from 4 h until 1 day post-injection (PI). Ser9-GSK3β and Ser133-cAMP responsive element-binding protein (CREB) phosphorylations showed similar spatiotemporal patterns in hippocampi at 1 day until 3 days PI. Double immunohistochemistry also showed that these phosphorylated forms of Akt, GSK3β and CREB were expressed in astrocytes. For the first time, our data demonstrate the injury-induced astrocytic changes in the levels of phosphorylation of Akt, -GSK3β and -CREB in vivo, which may reflect mechanisms of glial cells protection or adaptive response to damage. DW Kim and JH Lee contributed equally to this work.     

Diversity of Wolbachia isolated from the Cubitermes sp. affinis subarquatus complex of species (Termitidae), revealed by multigene phylogenies

Wolbachia are endosymbiotic bacteria that may alter the reproductive mechanisms of arthropod hosts. Eusocial termites provide considerable scope for Wolbachia studies owing to their ancient origin, their great diversity and their considerable ecological, biological and behavioral plasticity. This article describes the phylogenetic distribution of Wolbachia infecting termites of the Cubitermes genus, which are particularly abundant soil-feeders in equatorial Africa. Fourteen colonies of the Cubitermes sp. affinis subarquatus complex of species were screened using five bacterial genes (wsp, ftsZ, coxA, fbpA and 16S rRNA genes) and a striking diversity of Wolbachia strains was identified within these closely related species. In the host complex, three Wolbachia variants were found that were not in the super groups usually reported for termites (F and H), each infecting one or two Cubitermes species.     

E1 component of pyruvate dehydrogenase complex does not regulate the expression of NADPH-ferredoxin reductase in Azotobacter vinelandii

In Azotobacter vinelandii, the E1 component of pyruvate dehydrogenase complex (PDHE1) is proposed to be a key regulatory protein in an oxidative stress management system that responds to superoxide. This proposal was tested by constructing an A. vinelandii mutant that had a disruption of aceE gene encoding PDHE1. This mutant exhibited wild-type exponential growth and a normal response to oxidative stress induced by paraquat. Electrophoretic mobility-shift assays revealed that a protein previously shown to bind to a paraquat-activatable DNA promoter was still present in the extract prepared from the mutant, implying that the protein cannot be PDHE1. These observations strongly contradict the previous claim that PDHE1 is a DNA-binding protein that is directly involved in the A. vinelandii oxidative stress-regulatory system.     

Organization of butyrate synthetic genes in human colonic bacteria: phylogenetic conservation and horizontal gene transfer

Butyrate producers constitute an important bacterial group in the human large intestine. Butyryl-CoA is formed from two molecules of acetyl-CoA in a process resembling beta-oxidation in reverse. Three different arrangements of the six genes coding for this pathway have been found in low mol% G+C-content gram-positive human colonic bacteria using DNA sequencing and degenerate PCR. Gene arrangements were strongly conserved within phylogenetic groups defined by 16S rRNA gene sequence relationships. In the case of one of the genes, encoding beta-hydroxybutyryl-CoA dehydrogenase, however, sequence relationships were strongly suggestive of horizontal gene transfer between lineages. The newly identified gene for butyryl-CoA CoA-transferase, which performs the final step in butyrate formation in most known human colonic bacteria, was not closely linked to these central pathway genes.     

Cloning and functional expression of the gene encoding an inhibitor against <Emphasis Type="Italic">Aspergillus flavus</Emphasis> α-amylase,a novel seed lectin from <Emphasis Type="Italic">Lablab purpureus</Emphasis> (<Emphasis Type="Italic">Dolichos lablab</Emphasis>)

Maize is one of the more important agricultural crops in the world and, under certain conditions, prone to attack from pathogenic fungi. One of these, Aspergillus flavus, produces toxic and carcinogenic metabolites, called aflatoxins, as byproducts of its infection of maize kernels. The alpha-amylase of A. flavus is known to promote aflatoxin production in the endosperm of these infected kernels, and a 36-kDa protein from the Lablab purpureus, denoted AILP, has been shown to inhibit alpha-amylase production and the growth of A. flavus. Here, we report the isolation of six full-length labAI genes encoding AILP and a detailed analysis of the activities of the encoded proteins. Each of the six labAI genes encoded sequences of 274 amino acids, with the deduced amino acid sequences showing approximately 95-99% identity. The sequences are similar to those of lectin members of a legume lectin-arcelin-alpha-amylase inhibitor family reported to function in plant resistance to insect pests. The labAI genes did not show any of the structures characteristic of conserved structures identified in alpha-amylase inhibitors to date. The recombinant proteins of labAI-1 and labAI-2 agglutinated human red blood cells and inhibited A. flavus alpha-amylase in a manner similar to that shown by AILP. These data indicate that labAI genes are a new class of lectin members in legume seeds and that their proteins have both lectin and alpha-amylase inhibitor activity. These results are a valuable contribution to our knowledge of plant-pathogen interactions and will be applicable for developing protocols aimed at controlling A. flavus infection.     

Detecting the coevolution of biosequences--an example of RNA interaction prediction

A probabilistic graphical model is proposed in order to detect the coevolution between different sites in biological sequences. The model extends the continuous-time Markov process of sequence substitution for single nucleic or amino acids and imposes general constraints regarding simultaneous changes on the substitution rate matrix. Given a multiple sequence alignment for each molecule of interest and a phylogenetic tree, the model can predict potential interactions within or between nucleic acids and proteins. Initial validation of the model is carried out using tRNA and 16S rRNA sequence data. The model accurately identifies the secondary interactions of tRNA as well as several known tertiary interactions. In addition, results on 16S rRNA data indicate this general and simple coevolutionary model outperforms several other parametric and nonparametric methods in predicting secondary interactions. Furthermore, the majority of the putative predictions exhibit either direct contact or proximity of the nucleotide pairs in the 3-dimensional structure of the Thermus thermophilus ribosomal small subunit. The results on RNA data suggest a general model of coevolution might be applied to other types of interactions between protein, DNA, and RNA molecules.