The synaptic vesicle SNARE neuronal Synaptobrevin promotes endolysosomal degradation and prevents neurodegeneration

Soluble NSF attachment protein receptors (SNAREs) are the core proteins in membrane fusion. The neuron-specific synaptic v-SNARE n-syb (neuronal Synaptobrevin) plays a key role during synaptic vesicle exocytosis. In this paper, we report that loss of n-syb caused slow neurodegeneration independent of its role in neurotransmitter release in adult Drosophila melanogaster photoreceptor neurons. In addition to synaptic vesicles, n-Syb localized to endosomal vesicles. Loss of n-syb lead to endosomal accumulations, transmembrane protein degradation defects, and a secondary increase in autophagy. Our evidence suggests a primary defect of impaired delivery of vesicles that contain degradation proteins, including the acidification-activated Cathepsin proteases and the neuron-specific proton pump and V0 adenosine triphosphatase component V100. Overexpressing V100 partially rescued n-syb-dependent degeneration through an acidification-independent endosomal sorting mechanism. Collectively, these findings reveal a role for n-Syb in a neuron-specific sort-and-degrade mechanism that protects neurons from degeneration. Our findings further shed light on which intraneuronal compartments exhibit increased or decreased neurotoxicity.     

Origins and formation of histone methylation across the human cell cycle

The connections between various nuclear processes and specific histone posttranslational modifications are dependent to a large extent on the acquisition of those modifications after histone synthesis. The reestablishment of histone posttranslational modifications after S phase is especially critical for H3K9 and H3K27 trimethylation, both of which are linked with epigenetic memory and must be stably transmitted from one cellular generation to the next. This report uses a proteomic strategy to interrogate how and when the cell coordinates the formation of histone posttranslational modifications during division. Paramount among the findings is that H3K9 and H3K27 trimethylation begins during S phase but is completed only during the subsequent G(1) phase via two distinct pathways from the unmodified and preexisting dimethylated states. In short, we have systematically characterized the temporal origins and methylation pathways for histone posttranslational modifications during the cell cycle.     

Trinucleotide repeats are prevalent among cancer-related genes

Trinucleotide repeats (TNRs) have been primarily connected to neurologic and neuromuscular diseases, with few specific TNRs linked with various tumors. Here we conduct a genome-wide analysis and show that TNRs are five times more prevalent in cancer-related human genes. Interestingly, we also find that cancer-related genes are significantly longer than other genes. Our results suggest that genes containing TNRs are more prone to mutagenesis. The database of TNR genes can be used as a list of candidate cancer-related genes.     

Electron transfer properties of melanin.

Melanin synthesized from mushroom tyrosinase and 3,4-dihydroxyphenylalanine has been shown to oxidize NADH and NADPH, reduce ferricyanide, oxidized forms of cytochrome c and dichlorophenolindophenol, and catalyze the coupled oxidation of NADH and reduction of ferricyanide. Kinetic studies involving the determination of initial velocity at various concentrations of substrates and product inhibition measurements have been carried out on the NADH-ferricyanide-melanin reaction. The results are consistent with a ping-pong mechanism in which one product is formed prior to the reaction of melanin with the second substrate involving the reversible oxidation and reduction of melanin during the reaction. It may be concluded that melanin is capable of acting as an electron transfer agent in several reduction-oxidation systems.     

The bacteriophage P1 restriction endonuclease

The bacteriophage P1 restriction endonuclease has been purified from Escherichia coli lysogenic for P1. This restriction endonuclease P has a sedimentation coefficient of 9.3 S. Unlike the E. coli K restriction endonuclease, endonuclease P does not require S-adenosylmethionine for breakage of DNA. S-adenosylmethionine does, however, stimulate the rate of double-strand breakage of DNA by endonuclease P. Hydrolysis of ATP by endonuclease P could not be detected under conditions in which the K restriction endonuclease massively degrades ATP.The enzyme makes a limited number of double-strand breaks in unmodified or heterologously modified λ DNA. In the presence of S-adenosylmethionine, it does not cut every DNA molecule to the same extent. Incubation of λ DNA with excess amounts of enzyme in the presence of S-adenosylmethionine results in less breakage of the DNA than with smaller amounts of enzyme. This effect is not seen in the absence of S-adenosylmethionine. The maximum amount of cutting in the absence of S-adenosylmethionine appears to be greater than the maximum amount of cutting in its presence. This is most likely due to the modification methylase activity of P1 restriction endonuclease.     

A large degree of functional diversity exists among helper T cells specific for the same antigenic site of influenza hemagglutinin.

The site-1 determinant of the hemagglutinin molecule of influenza virus (A/PR/8/34) is one of several immunodominant sites in the BALB/c Th cell response to Ha. A synthetic peptide comprising this T cell site (HA110-120), a panel of analogs containing single substitutions in this determinant, and homologs truncated at the amino- or carboxyl-terminal were used to examine the fine specificities of 15 T cells specific for site-1 in the context of I-Ed. The results indicate that every residue within the minimal determinant plays a role in the T cell recognition process, as single substitutions at any of these positions affected the ability of the peptide to stimulate at least some site 1-specific T cells. For the majority of the residues examined, substitutions had dissimilar effects on distinct T cells, indicating that the substituted residues were affecting recognition in a receptor-specific manner. Each of the 15 T cells examined had a distinct fine specificity pattern, suggesting that the BALB/c T cell repertoire for this site is likely to exceed 100 distinct clonotypes.     

Interaction of mastoparan with the low molecular mass GTP-binding proteins rho/rac

Mastoparan, which has been shown to active G proteins, inhibits the ADP-ribosylation of 20 kDa human platelet membrane proteins catalyzed by Clostridium botulinum exoenzyme C3 half-maximally and maximally (90%) at 20 and 100 microM concentrations, respectively. Inhibition of ADP-ribosylation was enhanced by GTP-gamma S. Mastoparan increased GTP hydrolysis by porcine brain rho protein and stimulated GTP binding in a concentration dependent manner. The data suggest that mastoparan not only interacts with heterotrimeric G proteins but also with low molecular mass GTP-binding proteins of the rho/rac family.     

General description of Lake Peipsi-Pihkva

Neural networks and multiple linear regression models of the abundance of brown trout (Salmo trutta L.) on the mesohabitat scale were developed from combinations of physical habitat variables in 220 channel morphodynamic units (pools, riffles, runs, etc.) of 11 different streams in the central Pyrenean mountains. For all the 220 morphodynamic units, the determination coefficients obtained between the estimated and observed values of density or biomass were significantly higher for the neural network (r ² adjusted= 0.93 and r ² adjusted=0.92 (p<0.01) for biomass and density respectively with the neural network, against r ² adjusted=0.69 (p<0.01) and r ² adjusted = 0.54 (p<0.01) with multiple linear regression). Validation of the multivariate models and learning of the neural network developed from 165 randomly chosen channel morphodynamic units, was tested on the 55 other channel morphodynamic units. This showed that the biomass and density estimated by both methods were significantly related to the observed biomass and density. Determination coefficients were significantly higher for the neural network (r ² adjusted =0.72 (p<0.01) and 0.81 (p<0.01) for biomass and density respectively) than for the multiple regression model (r ² adjusted=0.59 and r ² adjusted=0.37 for biomass and density respectively). The present study shows the advantages of the backpropagation procedure with neural networks over multiple linear regression analysis, at least in the field of stochastic salmonid ecology.     

Pinocytotic response of circulating erythrocytes to specific blood grouping antibodies

Human blood samples from adults and newborns of blood groups O, A, and B were treated with either anti-A blood grouping serum, ferritin-conjugated anti-A serum, free ferritin, or saline and then prepared for electron microscopy. Morphological differences were observed between the untreated erythrocytes of infants and adults. Circulating red cells of newborns were frequently vesiculated (25.5%), whereas those of adults only occasionally showed vesicles (5.5%). On the basis of morphology and incidence, the majority of these vesiculated cells seemed to be mature erythrocytes. The introduction of anti-A serum to group A erythrocytes of infants appeared to stimulate vesicle formation, but anti-A serum did not have a similar effect on group O or B cells of infants or on group A cells of adults. Vesicles which formed in response to antiserum treatment appeared to be the result of pinocytosis. In contrast to the well dispersed ferritin along the membrane of agglutinated adult cells, the ferritin particles on the infants' cells were frequently clustered at irregular intervals. These accumulations seemed to lead to invaginations of the cell membrane, resulting in ferritin-lined intracytoplasmic vesicles. The addition of free ferritin or ferritin-conjugated antibodies of the wrong specificity to red cells did not increase vesicle formation.