S1P(2) receptors mediate inhibition of glioma cell migration through Rho signaling pathways independent of PTEN

Sphingosine 1-phosphate (S1P) induced the inhibition of glioma cell migration. Here, we characterized the signaling mechanisms involved in the inhibitory action by S1P. In human GNS-3314 glioblastoma cells, the S1P-induced inhibition of cell migration was associated with activation of RhoA and suppression of Rac1. The inhibitory action of S1P was recovered by a small interference RNA specific to S1P₂ receptor, a carboxyl-terminal region of Gα12 or Gα13, an RGS domain of p115RhoGEF, and a dominant-negative mutant of RhoA. The inhibitory action of S1P through S1P₂ receptors was also observed in both U87MG glioblastoma and 1321N1 astrocytoma cells, which have no protein expression of a phosphatase and tensin homolog deleted on chromosome 10 (PTEN). These results suggest that S1P₂ receptors/G_12/13-proteins/Rho signaling pathways mediate S1P-induced inhibition of glioma cell migration. However, PTEN, recently postulated as an indispensable molecule for the inhibition of cell migration, may not be critical for the S1P₂ receptor-mediated action in glioma cells.     

DNA polymerase eta reduces the gamma-H2AX response to psoralen interstrand crosslinks in human cells

DNA interstrand crosslinks are processed by multiple mechanisms whose relationships to each other are unclear. Xeroderma pigmentosum-variant (XP-V) cells lacking DNA polymerase eta are sensitive to psoralen photoadducts created under conditions favoring crosslink formation, suggesting a role for translesion synthesis in crosslink repair. Because crosslinks can lead to double-strand breaks, we monitored phosphorylated H2AX (gamma-H2AX), which is typically generated near double-strand breaks but also in response to single-stranded DNA, following psoralen photoadduct formation in XP-V fibroblasts to assess whether polymerase eta is involved in processing crosslinks. In contrast to conditions favoring monoadducts, conditions favoring psoralen crosslinks induced gamma-H2AX levels in both XP-V and nucleotide excision repair-deficient XP-A cells relative to control repair-proficient cells; ectopic expression of polymerase eta in XP-V cells normalized the gamma-H2AX response. In response to psoralen crosslinking, gamma-H2AX as well as 53BP1 formed coincident foci that were more numerous and intense in XP-V and XP-A cells than in controls. Psoralen photoadducts induced gamma-H2AX throughout the cell cycle in XP-V cells. These results indicate that polymerase eta is important in responding to psoralen crosslinks, and are consistent with a model in which nucleotide excision repair and polymerase eta are involved in processing crosslinks and avoiding gamma-H2AX associated with double-strand breaks and single-stranded DNA in human cells.     

Telmisartan prevented cognitive decline partly due to PPAR-gamma activation

Telmisartan is a unique angiotensin receptor blocker (ARB) and partial agonist of peroxisome proliferator-activated receptor (PPAR)-γ. Here, we investigated the preventive effect of telmisartan on cognitive decline in Alzheimer disease. In ddY mice, intracerebroventricular injection of Aβ 1-40 significantly attenuated their cognitive function evaluated by shuttle avoidance test. Pretreatment with a non-hypotensive dose of telmisartan significantly inhibited such cognitive decline. Interestingly, co-treatment with GW9662, a PPAR-γ antagonist, partially inhibited this improvement of cognitive decline. Another ARB, losartan, which has less PPAR-γ agonistic effect, also inhibited Aβ-injection-induced cognitive decline; however the effect was smaller than that of telmisartan and was not affected by GW9662. Immunohistochemical staining for Aβ showed the reduced Aβ deposition in telmisartan-treated mice. However, this reduction was not observed in mice co-administered GW9662. These findings suggest that ARB has a preventive effect on cognitive impairment in Alzheimer disease, and telmisartan, with PPAR-γ activation, could exert a stronger effect.     

Gramicidin S identified as a potent inhibitor for cytochrome bd-type quinol oxidase

Gramicidin S, a cationic cyclic decapeptide, exhibits the potent antibiotic activity through perturbation of lipid bilayers of the bacterial membrane. From the screening of natural antibiotics, we identified gramicidin S as a potent inhibitor for cytochrome bd-type quinol oxidase from Escherichia coli. We found that gramicidin S inhibited the oxidase with IC(50) of 3.5 microM by decreasing V(max) and the affinity for substrates but showed the stimulatory effect at low concentrations. Our findings would provide a new insight into the development of gramicidin S analogs, which do not share the target and mechanism with conventional antibiotics.     

Conserved repertoire of orthologous vomeronasal type 1 receptor genes in ruminant species

Background  

In mammals, pheromones play an important role in social and innate reproductive behavior within species. In rodents, vomeronasal receptor type 1 (V1R), which is specifically expressed in the vomeronasal organ, is thought to detect pheromones. The V1R gene repertoire differs dramatically between mammalian species, and the presence of species-specific V1R subfamilies in mouse and rat suggests that V1R plays a profound role in species-specific recognition of pheromones. In ruminants, however, the molecular mechanism(s) for pheromone perception is not well understood. Interestingly, goat male pheromone, which can induce out-of-season ovulation in anestrous females, causes the same pheromone response in sheep, and vice versa, suggesting that there may be mechanisms for detecting "inter-species" pheromones among ruminant species.     

Variability of intra- and interspecific competitions of bamboo stump mosquito larvae over small and large spatial scales

We carried out field experiments to examine the variability of interspecific competition of mosquito larvae among microcosms in a bamboo grove (small spatial scale) and between bamboo groves at two sites, with single and multiple mosquito species (large spatial scale). Four types of microcosms that differed in capacity and litter input were set. In the hillside bamboo grove, where multiple species occurred, succession of the predominant species from Aedes albopictus to Tripteroides bambusa was observed in control microcosms from which no mosquito larvae were removed. Weekly removal of competitive species resulted in increased pupation of A. albopictus and adult body weight under both rich and poor resource conditions. In the late period of the experiments, the effect of competitor removal on pupation of A. albopictus was greater in deep containers that never dried than in shallow containers that were dried in the laboratory. The number of eggs showed a slight difference between competitor‐excluded and deep control microcosms. These results indicate that interspecific competition limits pupation of A. albopictus more strongly in deep containers than in shallow and drought‐prone containers.
Compared with the hillside site, the larval density of A. albopictus attained a higher density in the bamboo grove in the plain where no competitive species occurred, due to a higher oviposition rate. Lower rate of pupation and lower adult weight at the plain site than at the hillside site indicated that resource limitation was more severe at the plain site. Populations of A. albopictus at hillside and plain sites appeared to suffer from strong inter‐ and intraspecific competition, respectively. At the hillside site, the intensity of interspecific competition appeared to increase later in the breeding season, with a high larval density of T. bambusa. In contrast, at the plain site, intensity of intraspecific competition appeared to be reduced later in the breeding season with decreasing larval density of A. albopictus.     

Crosstalk of prolyl isomerases, Pin1/Ess1, and cyclophilin A.

Previous studies have indicated that Ess1/Pin1, a gene in the parvulin family of peptidyl-prolyl isomerases (PPIases), plays an important role in regulating the G(2)/M transition of the cell cycle by binding cell-cycle-regulating proteins in eukaryotic cells. Although the ess1 gene has been considered to be essential in yeast, we have isolated viable ess1 deletion mutants and demonstrated, via analysis of yeast gene expression profiles using microarray techniques, a novel regulatory role for ESS1 in the G(1) phase. Although the overall expression profiles in the tested strains (C110-1, W303, S288c, and RAY-3AD) were similar, marked changes were detected for a number of genes involved in the molecular action of ESS1. Among these, the expression levels of a cyclophilin A gene, also a member of the PPIase family, increased in the ess1 null mutant derived from C110-1. Subsequent treatment with cyclosporin A significantly retarded growth, which suggests that ESS1 and cyclophilin A are functionally linked in yeast cells and play important roles at the G(1) phase of the cell cycle.     

Fourier-transform infrared studies on conformation changes in bd-type ubiquinol oxidase from Escherichia coli upon photoreduction of the redox metal centers.

Cytochrome bd is a two-subunit ubiquinol oxidase in the aerobic respiratory chain of Escherichia coli that does not belong to the heme-copper terminal oxidase superfamily. To explore unique protein structural changes associated with the reduction of the redox metal centers, we carried out Fourier-transform infrared and visible spectroscopic studies on cytochrome bd. For infrared measurements of a partially dehydrated thin sample solution, the air-oxidized enzyme was fully reduced by the intermolecular electron transfer of photo-excited riboflavin in the absence and presence of KCN, and redox difference spectra were calculated. Upon reduction, the bound cyanide was released from the heme b595-heme d binuclear center but remained in a protein pocket as a deprotonated form. Reduction of heme b558, heme b595, and heme d resulted in large changes in amide-I and protonated carboxylic CO-stretching vibrations and also a small change in the cysteine SH-stretching vibration. The location of the redox metal centers and the effects of cyanide suggest that these protein structural changes occur at the heme-binding pockets near the protein surface. Systematic site-directed mutagenesis and time-resolved FTIR studies on cytochrome bd will facilitate an understanding of the unique molecular mechanisms for dioxygen reduction and delivery of chemical protons to the active center at the atomic level.     

Species richness and altitudinal variation in the aquatic metazoan community in bamboo phytotelmata from north Sulawesi

We compared the aquatic metazoan community structure in bamboo stumps between a lowland (Kosinggolan; 200 m a.s.l.) and a highland site (Moat; 1030–1050 m a.s.l.) in North Sulawesi. The lowland bamboo stumps harbored 38 taxa including 2 predators, and the highland stumps harbored 35 taxa including 2 predators. In total 45 taxa were recorded, including 3 predators. Dominant detritivores were Tipulidae, Scirtidae, Chironomidae, Culicidae and Ceratopogonidae. The sole dominant predators wereToxorhynchites mosquito larvae, which occurred in 67% and 28% of stumps at the lowland and the highland sites, respectively. Although the mean biomass per stump did not differ significantly between the sites, the mean number of species per stump was significantly smaller at the lowland site. In addition, the variation in species composition among stumps was greater at the lowland site than at the highland site. Among dominant taxonomic groups, the number of non-predatory culicid species per stump was smaller at the lowland site where their predator,Toxorhynchites, was more abundant, although both sites had the same number of culicid species. In the presence ofToxorhynchites, the density and biomass of other culicids per stump were reduced significantly. The difference in predator density might affect differences in the local-scale community structure of individual bamboo stumps.