Neto2 Interacts with the Scaffolding Protein GRIP and Regulates Synaptic Abundance of Kainate Receptors

Kainate receptors (KARs) are a class of ionotropic glutamate receptors that are expressed throughout the central nervous system. The function and subcellular localization of KARs are tightly regulated by accessory proteins. We have previously identified the single-pass transmembrane proteins, Neto1 and Neto2, to be associated with native KARs. In the hippocampus, Neto1, but not Neto2, controls the abundance and modulates the kinetics of postsynaptic KARs. Here we evaluated whether Neto2 regulates synaptic KAR levels in the cerebellum where Neto1 expression is limited to the deep cerebellar nuclei. In the cerebellum, where Neto2 is present abundantly, we found a ∼40% decrease in GluK2-KARs at the postsynaptic density (PSD) of Neto2-null mice. No change, however, was observed in total level of GluK2-KARs, thereby suggesting a critical role of Neto2 on the synaptic localization of cerebellar KARs. The presence of a putative class II PDZ binding motif on Neto2 led us to also investigate whether it interacts with PDZ domain-containing proteins previously implicated in regulating synaptic abundance of KARs. We identified a PDZ-dependent interaction between Neto2 and the scaffolding protein GRIP. Furthermore, coexpression of Neto2 significantly increased the amount of GRIP associated with GluK2, suggesting that Neto2 may promote and/or stabilize GluK2:GRIP interactions. Our results demonstrate that Neto2, like Neto1, is an important auxiliary protein for modulating the synaptic levels of KARs. Moreover, we propose that the interactions of Neto1/2 with various scaffolding proteins is a critical mechanism by which KARs are stabilized at diverse synapses.     

Environmental stability affects phenotypic evolution in a globally distributed marine picoplankton

Marine phytoplankton can evolve rapidly when confronted with aspects of climate change because of their large population sizes and fast generation times. Despite this, the importance of environment fluctuations, a key feature of climate change, has received little attention—selection experiments with marine phytoplankton are usually carried out in stable environments and use single or few representatives of a species, genus or functional group. Here we investigate whether and by how much environmental fluctuations contribute to changes in ecologically important phytoplankton traits such as C:N ratios and cell size, and test the variability of changes in these traits within the globally distributed species Ostreococcus. We have evolved 16 physiologically distinct lineages of Ostreococcus at stable high CO₂ (1031±87 μatm CO₂, SH) and fluctuating high CO₂ (1012±244 μatm CO₂, FH) for 400 generations. We find that although both fluctuation and high CO₂ drive evolution, FH-evolved lineages are smaller, have reduced C:N ratios and respond more strongly to further increases in CO₂ than do SH-evolved lineages. This indicates that environmental fluctuations are an important factor to consider when predicting how the characteristics of future phytoplankton populations will have an impact on biogeochemical cycles and higher trophic levels in marine food webs.     

In vitro stabilization of 6-methylsalicylic acid synthetase from Penicillium urticae

In continuing studies of patulin biosynthesis, the first enzyme of the pathway, 6-methylsalicylic acid synthetase, was found to be far more labile than were the later enzymes of the pathway. Attempts were made to stabilize 6-methylsalicylic acid synthetase in vitro. The combined addition of the cofactor NADPH, the substrates acetyl-CoA and malonyl-CoA, the reducing agent dithiothreitol, and the proteinase inhibitor phenylmethylsulfonyl fluoride to cell-free extracts was found to prolong the half-life of the enzyme as much as 12-fold. This suggested that proteolysis and the conformational integrity of the enzyme may play an important role in controlling the duration of antibiotic biosynthesis in vivo. This was in agreement with the finding that the intracellular proteinase content of antibiotic-producing cells of Penicillium urticae rapidly increased just before the loss of 6-methylsalicylic acid synthetase content. These in vitro stabilization studies have provided some insight into the metabolic conditions that may stabilize these enzymes in vivo, and into possible ways of extending the life of these catalysts.     

Photooxidation of dinitrophenylhistidine-200 human carbonic anhydrase B.

Partial inactivation of tau-dinitrophenylhistidine-200 human carbonic anhydrase B, induced by visible light, followed first order kinetics (k(app) = 6.05 times 10-2 min-1). After 50 min the tau-dinitrophenylhistidine (tau-DNP-histidine) content decreased to a negligible level, but the illuminated enzyme retained, at pH 7.6, approximately 9.2 percent of the esterase activity of the native enzyme. The following lines of evidence suggest that the loss of activity results from the destruction of tau-DNP-histidine-200. (1) No significant loss of amino acid other than tau-DNP-histidine was detected after illumination. (2) The rate of loss of activity correlated well with the loss of tau-DNP-histidine. (3) In the photooxidized enzyme the DNP moiety was retained but had lost the characteristic sensitivity of tau-DNP-histidine to nucleophilic attack. Titration of the illuminated enzyme with acetazolamide indicated that the residual activity is an intrinsic property of the modified enzyme. The chromatographically purified photooxidized enzyme migrated as a single band on isoelectrofocusing in polyacylamide gel, and at pH 7.6 possessed 7.5 percent esterase activity relative to the native enzyme. By establishing effective destruction of histidine-200, it can be concluded that neither the pi N nor, as previously shown, the tau N of histidine-200 is critical for the catalysis.     

A yeast's eye view of mammalian reproduction: cross-species gene co-expression in meiotic prophase

Background  

Meiotic prophase is a critical stage in sexual reproduction. Aberrant chromosome recombination during this stage is a leading cause of human miscarriages and birth defects. However, due to the experimental intractability of mammalian gonads, only a very limited number of meiotic genes have been characterized. Here we aim to identify novel meiotic genes important in human reproduction through computational mining of cross-species and cross-sex time-series expression data from budding yeast, mouse postnatal testis, mouse embryonic ovary, and human fetal ovary.     

Effect of hyperthermia on growth of Ehrlich ascites tumor cells

Hyperthermic treatment at 43 degrees C suppressed the growth of Ehrlich ascites tumor (EAT) cells in vitro. Incubation of EAT cells at 43 degrees C for as little as 1.5 h totally abolished the transplantability of the tumor. At the same time, the rate of cellular glucose uptake, the density of glucose transporter on the cells as well as the extent of thymidine, uridine and leucine incorporation were significantly reduced.     

Effects of Δ8- and Δ9-Tetrahydrocannabinol on experimentally induced seizures

Effects of Δ⁸- and Δ⁹-tetrahydrocannabinol (Δ⁸- and Δ⁹-THC) on three experimentally induced seizure models, i.e., audiogenic seizure (AS) test, maximal electroshock seizure (MES) test and pentylenetetrazol (PTZ)-induced seizure test were determined in the audiogenic rat. Both tetrahydrocannabinols possess a dose-related anticonvulsant effect against AS, MES and PTZ-induced maximal seizure. Although anticonvulsant potencies do not significantly differ, Δ⁸THC is three times more neurotoxic than Δ⁹THC. In addition, both THC's are without effect on minimal seizure and lethality induced by PTZ. Furthermore, the low protective indexes (TD50/ED50) determined in this study suggest that Δ⁸ and Δ⁹ THC may have poor therapeutic potentials as antiepileptic drugs.     

Erratum to: Exogenous Adipokine Peptide Resistin Protects Against Focal Cerebral Ischemia/Reperfusion Injury in Mice

Neurochemical Research -     

Synthesis and in vitro anti Mycobacterium tuberculosis activity of a series of phthalimide derivatives

New phthalimide derivatives were easily prepared through condensation of phthalic anhydride and selected amines with variable yields (70–90%). All compounds (3a–l) were evaluated against Mycobacterium tuberculosis H₃₇Rv using Alamar Blue susceptibility. The compounds 3c, 3i, and 3l have the minimum inhibitory concentrations (MICs) of 3.9, 7.8, and 5.0 μg/mL, respectively, and could be considered new lead compounds in the treatment of tuberculosis and multi-drug resistant tuberculosis.