Expression of death-associated protein kinase and recruitment to the tumor necrosis factor signaling pathway following brief seizures

Death-associated protein (DAP) kinase is calcium-regulated and known to function downstream of death receptors, prompting us to examine its role in the mechanism of seizure-induced neuronal death. Brief seizures were focally evoked in rats, eliciting neuronal death within the CA3 subfield of the hippocampus, and to a lesser extent, cortex. Western blotting confirmed expression of DAP kinase within hippocampus and cortex at the predicted weight of approximately 160 kDa. Immunohistochemistry revealed seizures triggered a significant increase in numbers of DAP kinase-expressing cells within CA3 and cortex, without affecting cell counts within seizure-resistant CA2 or the dentate gyrus. Numbers of DAP kinase-expressing cells were increased in relation to specific patterns of injury-causing seizure activity, electrographically defined. Seizures caused an early increase in DAP kinase binding to actin, and association with calmodulin. Co-immunoprecipitation studies also revealed seizures triggered binding of DAP kinase to the tumor necrosis factor receptor 1 and the Fas-associated death domain protein, commensurate with caspase-8 proteolysis. In contrast, within surviving fields of the hippocampus, DAP kinase interacted with the molecular chaperone 14-3-3. These data suggest DAP kinase is involved in the molecular pathways activated during seizure-induced neuronal death.     

The association of cyclin A and cyclin kinase inhibitor p21 in response to gamma-irradiation requires the CDK2 binding region, but not the Cy motif

The cyclin kinase inhibitor p21 associates with and inhibits cyclin-CDKs to retard the progress of the cell cycle in response to DNA damage. The recognition sites for cyclin binding on the various cell cycle-related molecules have been identified as RXL motifs. In the case of p21, the dependence of the Cy1 (18CRRL) or Cy2 (154KRRL) motifs on cyclin E, but not on cyclin A has been demonstrated by in vitro experiments. In this study, to clarify the mechanism of p21 association with cyclin A, we constructed a p21 expression system in mammalian cells. After transfection with an expression vector containing cDNA of various p21-mutants, cells were irradiated with 10 Gy of gamma-rays to introduce DNA damage, followed by quantification of the p21-cyclin A association. The p21-mutant constructs were single or multiple deletions in Cy1, Cy2, and the CDK2 binding region, and a nonphosphorylatable alanine mutant of the C-terminal phosphorylation site. We demonstrated that the association of p21 and cyclin A in response to gamma-irradiation requires the CDK binding region, 49-71 aa, but not the Cy motifs. We believe the mechanism by which p21 inhibits cyclin-CDKs is distinct in each phase of the cell cycle. Furthermore, the increase in the association of p21 and cyclin A was not correlated with the levels of p21. This suggests that DNA damage triggers a signal to the p21 region between 21 and 96 aa to allow cyclin A association.     

Gustatory evoked cortical activity in humans studied by simultaneous EEG and MEG recording

Evoked potentials are widely used in clinical medicine for objective evaluation of sensory disturbances. However, gustatory evoked potentials (GEPs) have not been extensively studied due to lack of agreement among investigators regarding the waveforms. In this study GEPs and gustatory magnetic fields (GEMfs) were simultaneously recorded from five subjects in response to 0.3 M NaCl in an attempt to establish GEP recording as an objective gustatometer. Each subject received a total of 240 stimulus presentations over six sessions. Three GEP components (P1, N1 and P2) were observed and correlated with their corresponding equivalent current dipoles (ECD1, ECD2 and ECD3, respectively). ECD1 was localized to area G in all subjects, P1 being the indicator of intact gustatory projection to area G. No significant GEP activity was detected during the time preceding P1, which suggests that there was no activity in cortical gyri other than that detected by magnetoencephalography. ECD2 and ECD3 were localized to various cortical structures, including the inferior insula and the superior temporal sulcus, indicating that N1 and P2 reflect higher order gustatory functions. The present results indicate that measurement of GEPs may be useful for objective evaluation of gustatory disturbance.     

Potential changes with gamma-band oscillation at the frontal scalp elicited by intravenous olfactory stimulation in humans

Intravenous olfaction is a unique stimulation method often used in Japan to diagnose olfactory disturbances. Odorant is injected into a vein and transported by blood flow and respiration to the upper air tract. The intravenous olfaction might allow the potential at the frontal scalp to be recorded without contamination from electromyograms, such as those caused by sniffing. We injected Alinamin (thiamine propyldisulphide) into healthy subjects according to a standard protocol for clinical intravenous olfaction testing and we simultaneously recorded potential changes at the frontal scalp. When Alinamin was injected into the right median cubital vein over a 20 s period, the potential changes with gamma-band oscillations were detected 17.6 +/- 6.7 s (mean +/- SD) after the start of the injection. The main frequency component of this gamma-band oscillation is 30-160 Hz. The gamma-band oscillation elicited by intravenous olfactory stimulation (VOP) was similar to the induced wave of the olfactory bulb. Mapping the VOPs on the frontal scalp of a subject with less developed frontal sinuses and the relation between the thickness of the frontal sinuses and VOP amplitude suggest an intracranial source, possibly the olfactory bulb. The gamma-band potential at the frontal scalp is a useful measure of central disturbance.     

Suppression of antibody production by TNF-related apoptosis-inducing ligand (TRAIL)

TNF-related apoptosis-inducing ligand (TRAIL), a type II membrane protein belonging to the TNF family, induces apoptotic cell death in various types of tumor cells. However, little is known about its pathological and physiological functions in the immune system. In this study, we showed that administration of neutralizing anti-TRAIL mAb markedly increased serum auto-Ab levels, particularly of IgG1 subclass, in autoimmune-prone C3H/HeJ gld/gld mice without affecting lymphocytosis and lymphocytes populations. In an experimental system where TNP-specific Ab production was induced by immunization with TNP-modified syngeneic B lymphoma cells, expression of TRAIL on these cells significantly reduced TNP-specific Ab production, especially of IgG1 subclass, without affecting T cell priming. These results suggest a new role for TRAIL in the suppression of Ab production.     

Acrosome reaction in spermatozoa from hagfish (Agnatha) Eptatretus burgeri and Eptatretus stouti: acrosomal exocytosis and identification of filamentous actin

Spermatozoa of the hagfishes Eptatretus burgeri and Eptatretus stouti, caught in the sea near Japan and North America, respectively, were found to undergo the acrosome reaction, which resulted in the formation of an acrosomal process with a filamentous core. The acrosomal region of spermatozoa of E. stouti exhibited immunofluorescent labeling using an actin antibody. The midpiece also labeled with the antibody. The acrosomal region showed a similar labeling pattern when sperm were probed with tetramethylrhodamine isothyocyanate (TRITC)-phalloidin; the midpiece did not label. Following induction of the acrosome reaction with the calcium (Ca2+) ionophore ionomycin, TRITC-phalloidin labeling was more intense in the acrosomal region, suggesting that the polymerization of actin occurs during formation of the acrosomal process, as seen in many invertebrates. The potential for sperm to undergo acrosomal exocytosis was already acquired by late spermatids. During acrosomal exocytosis, the outer acrosomal membrane and the overlying plasma membrane disappeared and were replaced by an array of vesicles; these resembled an early stage of the acrosome reaction in spermatozoa of higher vertebrates in which no formation of an acrosomal process occurs. It is phylogenetically interesting that such phenomena occur in spermatozoa of hagfish, a primitive vertebrate positioning between invertebrates and high vertebrates.     

Specific recognition and cleavage of galectin-3 by Leishmania major through species-specific polygalactose epitope

Lipophosphoglycan is a major surface molecule of Leishmania, protozoa parasites, which are the causative agents of leishmaniasis, a disease that annually afflicts millions of people worldwide. The oligosaccharide structures of lipophosphoglycan varies among species, and epitopes of these species-specific oligosaccharides are suggested to be implicated in the interaction of Leishmania with macrophages as well as species-specific tissue tropism observed in leishmaniasis. The recognition of the species-specific variation of oligosaccharides is likely to be mediated by host carbohydrate-binding proteins, lectins, but the identities of the lectins remain elusive. Galectin-3 is a mammalian soluble beta-galactoside-binding lectin and is expressed in macrophages, dendritic cells, and keratinocytes, as well as fibroblasts, all of which are present in the site of Leishmania infection. In this paper, we found that galectin-3 binds to lipophosphoglycan of Leishmania major but not to those of Leishmania donovani through L. major-specific polygalactose epitopes. Association of galectin-3 with L. major led to the cleavage of galectin-3, resulting in truncated galectin-3 containing the C-terminal lectin domain but lacking the N-terminal domain implicated in lectin oligomerization. This cleavage was inhibited by the galectin-3 antagonist lactose, as well as 1,10-ortho-phenanthroline, suggesting that galectin-3 is cleaved by zinc metalloproteases after its binding to lipophosphoglycans. The modulation of various innate immunity reactions by galectin-3 is affected by its oligomerization; therefore, we propose the L. major-specific truncation of galectin-3 may contribute to the species-specific immune responses induced by Leishmania.     

Phosphorylation of neuroglycan C, a brain-specific transmembrane chondroitin sulfate proteoglycan, and its localization in the lipid rafts

Neuroglycan C (NGC) is a brain-specific transmembrane chondroitin sulfate proteoglycan. In the present study, we examined whether NGC could be phosphorylated in neural cells. On metabolic labeling of cultured cerebral cortical cells from the rat fetus with (32)P(i), serine residues in NGC were radiolabeled. Some NGC became detectable in the raft fraction from the rat cerebrum, a signaling microdomain of the plasma membrane, with cerebral development. NGC from the non-raft fraction, not the raft fraction, could be phosphorylated by an in vitro kinase reaction. The phosphorylation of NGC was inhibited by adding to the reaction mixture a recombinant peptide representing the ectodomain of NGC, but not by adding a peptide representing its cytoplasmic domain. NGC could be labeled by an in vitro kinase reaction using [gamma-(32)P]GTP as well as [gamma-(32)P]ATP, and this kinase activity was partially inhibited by 5,6-dichloro-1-beta-d-ribofuranosylbenzimidazole, a selective inhibitor of casein kinase II. In addition to the intracellular phosphorylation, NGC was also phosphorylated at the cell surface by an ectoprotein kinase. This is the first report to demonstrate that NGC can be phosphorylated both intracellularly and pericellularly, and our findings suggest that a kinase with a specificity similar to that of casein kinase II is responsible for the NGC ectodomain phosphorylation.