Taurine in the marine hydrozoan Hydractinia echinata: stabilizer of the larval state?

Glycine as a signaling molecule and chemoattractant in Trichoplax (Placozoa): insights into the early evolution of neurotransmitters

The origin and early evolution of neurotransmitter signaling in animals are unclear due to limited comparative information, primarily about prebilaterian animals. Here, we performed the comparative survey of signal molecules in placozoans - the simplest known free-living animals without canonical synapses, but with complex behaviors. First, using capillary electrophoresis with laser-induced fluorescence detection, we performed microchemical analyses of transmitter candidates in Trichoplax adhaerens - the classical reference species in comparative biology. We showed that the endogenous level of glycine (about 3 mM) was significantly higher than for other candidates such as L-glutamate, L-aspartate, or gamma-aminobutyric acid. Neither serotonin nor dopamine were detected. The absolute glycine concentrations in Trichoplax were even higher than we measured in ctenophores (Beroe) and cnidarians (Aequorea). We found that at millimolar concentrations of glycine (similar to the endogenous level), induced muscle-like contractions in free behaving animals. But after long incubation (24 h), 10 M of glycine could induce cytotoxicity and cell dissociation. In contrast, micromolar concentrations (10-10 M) increased Trichoplax ciliated locomotion, suggesting that glycine might act as an endogenous signal molecule. However, we showed than glycine (10 M) can also be a chemoattractant (a guiding factor for food sources), and therefore, act as the exogenous signal. These findings provide an evolutionary base for the origin of transmitters as a result of the interplay between exogenous and endogenous signaling systems early in animal evolution.

Molecular characterization of the apical organ of the anthozoan Nematostella vectensis

Apical organs are sensory structures present in many marine invertebrate larvae where they are considered to be involved in their settlement, metamorphosis and locomotion. In bilaterians they are characterised by a tuft of long cilia and receptor cells and they are associated with groups of neurons, but their relatively low morphological complexity and dispersed phylogenetic distribution have left their evolutionary relationship unresolved. Moreover, since apical organs are not present in the standard model organisms, their development and function are not well understood. To provide a foundation for a better understanding of this structure we have characterised the molecular composition of the apical organ of the sea anemone Nematostella vectensis. In a microarray-based comparison of the gene expression profiles of planulae with either a wildtype or an experimentally expanded apical organ, we identified 78 evolutionarily conserved genes, which are predominantly or specifically expressed in the apical organ of Nematostella. This gene set comprises signalling molecules, transcription factors, structural and metabolic genes. The majority of these genes, including several conserved, but previously uncharacterized ones, are potentially involved in different aspects of the development or function of the long cilia of the apical organ. To demonstrate the utility of this gene set for comparative analyses, we further analysed the expression of a subset of previously uncharacterized putative orthologs in sea urchin larvae and detected expression for twelve out of eighteen of them in the apical domain. Our study provides a molecular characterization of the apical organ of Nematostella and represents an informative tool for future studies addressing the development, function and evolutionary history of apical organ cells.

β-Alanine suppresses heat inactivation of lactate dehydrogenase

Beta-Alanine exhibits neurotransmitter activity and is a component of the anti-glycation agent carnosine. We propose that beta-alanine may have additional properties which may be of physiological significance. Interestingly, stress modulates the level of beta-alanine, which regulates excitotoxicity responses and prevents neuronal cell death. We hypothesize that beta-alanine's protective role may involve preservation of enzyme structure and function, suggesting that beta-alanine may act as a chemical chaperone. We used light scattering, enzyme activity and intrinsic fluorescence to monitor heat-induced changes in lactate dehydrogenase (LDH) in the presence and absence of beta-alanine. We observed that beta-alanine suppressed heat-induced LDH inactivation, prevented LDH aggregation, ameliorated the decrease in intrinsic fluorescence and reactivated thermally denatured LDH. These observations support the hypothesis that beta-alanine has chaperone-like activity and may play a cellular role in the preservation of enzyme function.

Marine natural products from the Turkish sponge Agelas oroides that inhibit the enoyl reductases from Plasmodium falciparum, Mycobacterium tuberculosis and Escherichia coli

The type II fatty acid pathway (FAS-II) is a validated target for antimicrobial drug discovery. An activity-guided isolation procedure based on Plasmodium falciparum enoyl-ACP reductase (PfFabI) enzyme inhibition assay on the n-hexane-, the CHCl(3-) and the aq MeOH extracts of the Turkish marine sponge Agelas oroides yielded six pure metabolites [24-ethyl-cholest-5alpha-7-en-3-beta-ol (1), 4,5-dibromopyrrole-2-carboxylic acid methyl ester (2), 4,5-dibromopyrrole-2-carboxylic acid (3), (E)-oroidin (4), 3-amino-1-(2-aminoimidazoyl)-prop-1-ene (5), taurine (6)] and some minor, complex fatty acid mixtures (FAMA-FAMG). FAMA, consisting of a 1:2 mixture of (5Z,9Z)-5,9-tricosadienoic (7) and (5Z,9Z)-5,9-tetracosadienoic (8) acids, and FAMB composed of 8, (5Z,9Z)-5,9-pentacosadienoic (9) and (5Z,9Z)-5,9-hexacosadienoic (10) acids in approximately 3:3:2 ratio were the most active PfFabI inhibitory principles of the hexane extract (IC(50) values 0.35 microg/ml). (E)-Oroidin isolated as free base (4a) was identified as the active component of the CHCl(3) extract. Compound 4a was a more potent PfFabI inhibitor (IC(50) 0.30 microg/ml=0.77 microM) than the (E)-oroidin TFA salt (4b), the active and major component of the aq MeOH extract (IC(50) 5.0 microg/ml). Enzyme kinetic studies showed 4a to be an uncompetitive PfFabI inhibitor (K(i): 0.4+/-0.2 and 0.8+/-0.2 microM with respect to substrate and cofactor). In addition, FAMA and FAMD (mainly consisting of methyl-branched fatty acids) inhibited FabI of Mycobacterium tuberculosis (MtFabI, IC(50)s 9.4 and 8.2 microg/ml, respectively) and Escherichia coli (EcFabI, IC(50)s 0.5 and 0.07 microg/ml, respectively). The majority of the compounds exhibited in vitro antiplasmodial, as well as trypanocidal and leishmanicidal activities without cytotoxicity towards mammalian cells. This study represents the first marine metabolites that inhibit FabI, a clinically relevant enzyme target from the FAS-II pathway of several pathogenic microorganisms.

Phototrophic utilization of taurine by the purple nonsulfur bacteria Rhodopseudomonas palustris and Rhodobacter sphaeroides

Taurine metabolism by two phototrophically grown purple nonsulfur bacteria enrichment isolates has been examined.Rhodopseudomonas palustris(strain Tau1) grows with taurine as a sole electron donor, sulfur and nitrogen source during photoautotrophic growth.Rhodobacter sphaeroides(strain Tau3) grows on the compound as sole electron donor, sulfur and nitrogen source, and partial carbon source, in the presence of CO2during photoheterotrophic growth. Both organisms utilize an inducible taurine–pyruvate aminotransferase and a sulfoacetaldehyde acetyltransferase. The products of this metabolism are bisulfite and acetyl phosphate. Bisulfite ultimately was oxidized to sulfate, but this was not an adequate source of electrons for photometabolism. Experiments using either [U-14C]taurine or14CO2demonstrated thatRb. sphaeroidesTau3 assimilated the carbon from approximately equimolar amounts of taurine and exogenous CO2. The taurine-carbon assimilation was not diminished by excess non-radioactive bicarbonate. Malate synthase (but not isocitrate lyase) was induced in these taurine-grown cells. It is concluded that assimilation of taurine carbon occurs through an intermediate other than CO2. Similar labelling experiments withRp. palustrisTau1 determined that taurine is utilized only as an electron donor for the reduction of CO2, which contributes all the cell carbon. Photoautotrophic metabolism was confirmed in this organism by the absence of either malate synthase or isocitrate lyase in taurine+CO2-grown cells. Culture collection strains of these two bacteria did not utilize taurine in these fashions.