Abstract. The machinery of eukaryotic protein synthesis is found in association with the actin cytoskeleton. A major component of this translational apparatus, which is involved in the shuttling of aa-tRNA, is the actinbinding protein elongation factor let (EF-let). To investigate the consequences for translation of the interaction of EF-let with F-actin, we have studied the effect of F-actin on the ability of EF-let to bind to aa-tRNA. We demonstrate that binding of EF-let:GTP to aatRNA is not pH sensitive with a constant binding affinity of ~0.2 ~M over the physiological range of pH. However, the sharp pH dependence of binding of EF-let to F-actin is sufficient to shift the binding of EFlet from F-actin to aa-tRNA as pH increases. The ability of EF-let to bind either F-actin or aa-tRNA in competition binding experiments is also consistent with the observation that EF-let's binding to F-actin and aatRNA is mutually exclusive. Two pH-sensitive actinbinding sequences in EF-let are identified and are predicted to overlap with the aa-tRNA-binding sites. Our results suggest that pH-regulated recruitment and release of EF-let from actin filaments in vivo will supply a high local concentration of EF-let to facilitate polypeptide elongation by the F-actin-associated translational apparatus.

After accumulation of data showing that resident brain cells (neurons, astrocytes, and microglia) produce mediators of the immune system, such as cytokines and their receptors under normal physiological conditions, a critical need emerged for investigating the role of these mediators in cognitive processes. The major problem for understanding the functional role of cytokines in the mechanisms of synaptic plasticity, de novo neurogenesis, and learning and memory is the small number of investigated cytokines. Existing concepts are based on data from just three proinflammatory cytokines: interleukin-1 beta, interleukin-6, and tumor necrosis factor-alpha. The amount of information in the literature on the functional role of antiinflammatory cytokines in the mechanisms of synaptic plasticity and cognitive functions of mature mammalian brain is dismally low. However, they are of principle importance for understanding the mechanisms of local information processing in the brain, since they modulate the activity of individual cells and local neural networks, being able to reconstruct the processes of synaptic plasticity and intercellular communication, in general, depending on the local ratio of the levels of different cytokines in certain areas of the brain. Understanding the functional role of cytokines in cellular mechanisms of information processing and storage in the brain would allow developing preventive and therapeutic means for the treatment of neuropathologies related to impairment of these mechanisms.

Three-dimensional structural models of three members of the phosphoglucomutase (PGM) superfamily, parafusin, phosphoglucomutase-related protein and sarcoplasmic reticulum phosphoglucomutase, were constructed by homology modeling based on the known crystal structure of rabbit muscle phosphoglucomutase. Parafusin, phosphoglucomutase-related protein and sarcoplasmic reticulum phosphoglucomutase each have 50% or more identity with rabbit muscle phosphoglucomutase at the amino acid level and all are reported to exhibit no or minor phosphoglucomutase activity. There are four major insertions and two deletions in the parafusin sequence relative to PGM, all of which are located in surface-exposed loops connecting secondary structural elements. The remaining amino acid substitutions are distributed throughout the sequence and are not predicted to alter the polypeptide fold. Parafusin contains a putative protein kinase C site located on a surface loop in domain II that is not present in the homologs. Although the general domain structure and the active site of rabbit muscle phosphoglucomutase are preserved in the model of phosphoglucomutase-related protein, a major structural difference is likely to occur in domain 1 due to the absence of 55 amino acid residues in PGM-RP. This deletion predicts the loss of three alpha-helices and one beta-strand from an anti-parallel beta-sheet in this domain as compared with the rabbit muscle phosphoglucomutase.

The comparative effects of the anti-inflammatory cytokine interleukin-10 on the development of epileptiform activity were studied in hippocampal field CA1 neurons in different models of epileptogenesis not accompanied by visible morphological lesions in brain cells: 1) a model of hypoxic kindling in rat hippocampal slices; 2) a disinhibitory model of epileptogenesis in rat hippocampal slices using the GABAA receptor blocker bicuculline; and 3) a partial electrical kindling model in intact rats. Interleukin-10 (1 ng/ml) blocked the development of post-hypoxic hyperexcitability of field CA1 pyramidal neurons in hippocampal slices, decreasing the effectiveness of hypoxia in suppressing neuron activity during the hypoxic episode. Interleukin-10 had no effect on the initiation of epileptiform activity in pyramidal neurons induced by the proconvulsant bicuculline. Single intrahippocampal injections of interleukin-10 at a dose of 1 ng in 5 microl suppressed the development of focal convulsions ("ictal" discharges) at the stimulation site in partial kindling in freely moving animals for several hours after administration. However, this cytokine had no effect on the duration of the "interictal" component of focal afterdischarges or on the severity of behavioral seizures. These results show that the anti-inflammatory cytokine interleukin-10, at the concentrations used here, has not only antihypoxic activity, but also a protective effect in relation to the initiation of the "ictal," but not the "interictal" component of epileptiform activity in hippocampal neurons.

The aim of the present work was to study the effects of interleukin-10 at concentrations of 1 and 10 ng/ml on the development of epileptiform discharges evoked in pyramidal neurons in field CA3 in rat hippocampal slices by transient episodes of hypoxia. Three 3-min episodes of hypoxia led to decreases in the generation threshold for evoked trains of population spikes and an increase in the number of population spikes per train in pyramidal neurons of field CA1. Interleukin-10 at a concentration of 1 ng/ml completely eliminated the development of epileptiform activity, while its protective effect was less marked at a concentration of 10 ng/ml. These effects of interleukin-10 on living hippocampal slices in in vitro conditions show that they may be associated with the functions of this cytokine as an intercellular mediator of the central nervous system itself rather than being mediated by the peripheral immune system. The results of these studies provide the first experimental evidence of the action of the anti-inflammatory cytokine interleukin-10 on the development of hypoxia-evoked epileptiform events in the hippocampus.