Glutathione aerosol suppresses lung epithelial surface inflammatory cell-derived oxidants in cystic fibrosis.

Cystic fibrosis (CF) is characterized by accumulation of activated neutrophils and macrophages on the respiratory epithelial surface (RES); these cells release toxic oxidants, which contribute to the marked epithelial derangements seen in CF. These deleterious consequences are magnified, since reduced glutathione (GSH), an antioxidant present in high concentrations in normal respiratory epithelial lining fluid (ELF), is deficient in CF ELF. To evaluate the feasibility of increasing ELF GSH levels and enhancing RES antioxidant protection, GSH aerosol was delivered (600 mg twice daily for 3 days) to seven patients with CF. ELF total, reduced, and oxidized GSH increased (P < 0.05, all compared with before GSH therapy), suggesting adequate RES delivery and utilization of GSH. Phorbol 12-myristate 13-acetate-stimulated superoxide anion (O2-.) release by ELF inflammatory cells decreased after GSH therapy (P < 0.002). This paralleled observations that GSH added in vitro to CF ELF inflammatory cells suppressed O2-. release (P < 0.001). No adverse effects were noted during treatment. Together, these observations demonstrate the feasibility of using GSH aerosol to restore RES oxidant-antioxidant balance in CF and support the rationale for further clinical evaluation.     

Bidirectional Control of Postsynaptic Density-95 (PSD-95) Clustering by Huntingtin

Huntington disease is associated with early alterations in corticostriatal synaptic function that precede cell death, and it is postulated that ameliorating such changes may delay clinical onset and/or prevent neurodegeneration. Although many of these synaptic alterations are thought to be attributable to a toxic gain of function of the mutant huntingtin protein, the role that nonpathogenic huntingtin (HTT) plays in synaptic function is relatively unexplored. Here, we compare the immunocytochemical localization of a major postsynaptic scaffolding protein, PSD-95, in striatal neurons from WT mice and mice overexpressing HTT with 18 glutamine repeats (YAC18, nonpathogenic). We found that HTT overexpression resulted in a palmitoylation- and BDNF-dependent increase in PSD-95 clustering at synaptic sites in striatal spiny projection neurons (SPNs) co-cultured with cortical neurons. Surprisingly, the latter effect was mediated presynaptically, as HTT overexpression in cortical neurons alone was sufficient to increase PSD-95 clustering in the postsynaptic SPNs. In contrast, antisense oligonucleotide knockdown of HTT in WT co-cultures resulted in a significant reduction of PSD-95 clustering in SPNs. Notably, despite these bidirectional changes in PSD-95 clustering, we did not observe an alteration in basal electrophysiological measures of AMPA and NMDA receptors. Thus, unlike in previous studies in the hippocampus, enhanced or decreased PSD-95 clustering alone was insufficient to drive AMPA or NMDA receptors into or out of SPN synapses. In all, our results demonstrate that nonpathogenic HTT can indeed influence synaptic protein localization and uncover a novel role of HTT in PSD-95 distribution.     

Overexpression of the endoplasmic reticulum 60 protein ER-60 downregulates apoB100 secretion by inducing its intracellular degradation via a nonproteasomal pathway: evidence for an ER-60-mediated and pCMB-sensitive intracellular degradative pathway

Co- and posttranslational regulation of apolipoprotein B (apoB) has been postulated to involve degradation by both proteasomal and nonproteasomal pathways; however, nonproteasomal mechanisms of apoB degradation are currently unknown. We have previously demonstrated an intracellular association of newly synthesized apoB with endoplasmic reticulum (ER)-60, an ER-localized protein, possessing both proteolytic and chaperone activities. In the present paper, adenoviral expression vectors containing rat ER-60 cDNA were used to achieve dose- and time-dependent overexpression of ER-60 to investigate its role in apoB100 turnover. Overexpressed ER-60 accumulated in the microsomal lumen of HepG2 cells and was associated with apoB100 in dense lipoprotein particles. Overexpression of ER-60 in HepG2 cells significantly reduced both intracellular and secreted apoB100, with no effect on the secretion of a control protein, albumin. Similar results were obtained in McA-RH7777 rat hepatoma cells. ER-60-stimulated apoB100 degradation and inhibition of apoB100 secretion were sensitive to the protease inhibitor, p-chloromercuribenzoate (pCMB), in a dose-dependent manner but were unaffected by the proteasomal or lysosomal protease inhibitors, N-acetyl-leucinyl-leucinyl-nor-leucinal, E64, and leupeptin. Interestingly, enhanced expression of ER-60 induced apoB100 fragmentation in permeabilized HepG2 cells and resulted in detection of a unique 50 kDa degradation intermediate, a process that could be inhibited by pCMB. Intracellular stability and secretion of apoB100 in primary hamster hepatocytes were also found to be sensitive to pCMB. When taken together, the data suggest an important role for ER-60 in promoting apoB100 degradation via a pCMB-sensitive process in the ER. ER-60 may act directly as a protease or may be involved indirectly as a chaperone/protein factor targeting apoB100 to this nonproteasomal and pCMB-sensitive degradative pathway.     

Prohibitin (PHB) inhibits apoptosis in rat granulosa cells (GCs) through the extracellular signal-regulated kinase 1/2 (ERK1/2) and the Bcl family of proteins

Mammalian ovarian follicular development is tightly regulated by crosstalk between cell death and survival signals, which include both endocrine and intra-ovarian regulators. Whether the follicle ultimately ovulates or undergoes atresia is dependent on the expression and actions of factors promoting follicular cell proliferation, differentiation or apoptosis. Prohibitin (PHB) is a highly conserved, ubiquitous protein that is abundantly expressed in granulosa cells (GCs) and associated with GC differentiation and apoptosis. The current study was designed to characterize the regulation of anti-apoptotic and pro-apoptotic factors in undifferentiated rat GCs (gonadotropin independent phase) governed by PHB. Microarray technology was initially employed to identify potential apoptosis-related genes, whose expression levels within GCs were altered by either staurosporine (STS) alone or STS in presence of ectopically over-expressed PHB. Next, immunoblot studies were performed to examine the expression patterns of selective Bcl-2 family members identified by the microarray analysis, which are commonly regulated in the intrinsic-apoptotic pathway. These studies were designed to measure protein levels of Bcl2 family in relation to expression of the acidic isoform (phosphorylated) PHB and the components of MEK-Erk1/2 pathway. These studies indicated that over-expression of PHB in undifferentiated GCs inhibit apoptosis which concomitantly results in an increased level of the anti-apoptotic proteins Bcl2 and Bclxl, reduced release of cytochrome c from mitochondria and inhibition of caspase-3 activity. In contrast, silencing of PHB expression resulted in change of mitochondrial morphology from the regular reticular network to a fragmented form, which enhanced sensitization of these GCs to the induction of apoptosis. Collectively, these studies have provided new insights on the PHB-mediated anti-apoptotic mechanism, which occurs in undifferentiated GCs through a PHB → Mek-Erk1/2 → Bcl/Bcl-xL pathway and may have important clinical implications.     

The Cleaved N-Terminus of pVI Binds Peripentonal Hexons in Mature Adenovirus

Mature human adenovirus particles contain four minor capsid proteins, in addition to the three major capsid proteins (penton base, hexon and fiber) and several proteins associated with the genomic core of the virion. Of the minor capsid proteins, VI plays several crucial roles in the infection cycle of the virus, including hexon nuclear targeting during assembly, activation of the adenovirus proteinase (AVP) during maturation and endosome escape following cell entry. VI is translated as a precursor (pVI) that is cleaved at both N- and C-termini by AVP. Whereas the role of the C-terminal fragment of pVI, pVIc, is well established as an important co-factor of AVP, the role of the N-terminal fragment, pVIn, is currently elusive. In fact, the fate of pVIn following proteolytic cleavage is completely unknown. Here, we use a combination of proteomics-based peptide identification, native mass spectrometry and hydrogen–deuterium exchange mass spectrometry to show that pVIn is associated with mature human adenovirus, where it binds at the base of peripentonal hexons in a pH-dependent manner. Our findings suggest a possible role for pVIn in targeting pVI to hexons for proper assembly of the virion and timely release of the membrane lytic mature VI molecule.     

Similarity of Cortical Activity Patterns Predicts generalization Behavior

Humans and animals readily generalize previously learned knowledge to new situations. Determining similarity is critical for assigning category membership to a novel stimulus. We tested the hypothesis that category membership is initially encoded by the similarity of the activity pattern evoked by a novel stimulus to the patterns from known categories. We provide behavioral and neurophysiological evidence that activity patterns in primary auditory cortex contain sufficient information to explain behavioral categorization of novel speech sounds by rats. Our results suggest that category membership might be encoded by the similarity of the activity pattern evoked by a novel speech sound to the patterns evoked by known sounds. Categorization based on featureless pattern matching may represent a general neural mechanism for ensuring accurate generalization across sensory and cognitive systems.     

The Efficacy of the BCG Vaccine against Newly Emerging Clinical Strains of Mycobacterium tuberculosis

To date, most new vaccines against Mycobacterium tuberculosis, including new recombinant versions of the current BCG vaccine, have usually been screened against the laboratory strains H37Rv or Erdman. In this study we took advantage of our recent work in characterizing an increasingly large panel of newly emerging clinical isolates [from the United States or from the Western Cape region of South Africa], to determine to what extent vaccines would protect against these [mostly high virulence] strains. We show here that both BCG Pasteur and recombinant BCG Aeras-422 [used here as a good example of the new generation BCG vaccines] protected well in both mouse and guinea pig low dose aerosol infection models against the majority of clinical isolates tested. However, Aeras-422 was not effective in a long term survival assay compared to BCG Pasteur. Protection was very strongly expressed against all of the Western Cape strains tested, reinforcing our viewpoint that any attempt at boosting BCG would be very difficult to achieve statistically. This observation is discussed in the context of the growing argument made by others that the failure of a recent vaccine trial disqualifies the further use of animal models to predict vaccine efficacy. This viewpoint is in our opinion completely erroneous, and that it is the fitness of prevalent strains in the trial site area that is the centrally important factor, an issue that is not being addressed by the field.     

Mutational analysis of the purine riboswitch aptamer domain

The purine riboswitch is one of a number of mRNA elements commonly found in the 5'-untranslated region capable of controlling expression in a cis-fashion via its ability to directly bind small-molecule metabolites. Extensive biochemical and structural analysis of the nucleobase-binding domain of the riboswitch, referred to as the aptamer domain, has revealed that the mRNA recognizes its cognate ligand using an intricately folded three-way junction motif that completely encapsulates the ligand. High-affinity binding of the purine nucleobase is facilitated by a distal loop-loop interaction that is conserved between both the adenine and guanine riboswitches. To understand the contribution of conserved nucleotides in both the three-way junction and the loop-loop interaction of this RNA, we performed a detailed mutagenic survey of these elements in the context of an adenine-responsive variant of the xpt-pbuX guanine riboswitch from Bacillus subtilis. The varying ability of these mutants to bind ligand as measured by isothermal titration calorimetry uncovered the conserved nucleotides whose identity is required for purine binding. Crystallographic analysis of the bound form of five mutants and chemical probing of their free state demonstrate that the identity of several universally conserved nucleotides is not essential for formation of the RNA-ligand complex but rather for maintaining a binding-competent form of the free RNA. These data show that conservation patterns in riboswitches arise from a combination of formation of the ligand-bound complex, promoting an open form of the free RNA, and participating in the secondary structural switch with the expression platform.