Electrostatically constrained alpha-helical peptide inhibits replication of HIV-1 resistant to enfuvirtide

Alpha-helical peptides, such as T-20 (enfuvirtide) and C34, derived from the gp41 carboxyl-terminal heptad repeat (C-HR) of HIV-1, inhibit membrane fusion of HIV-1 and the target cells. Although T-20 effectively suppresses the replication of multi-drug resistant HIV variants both in vitro and in vivo, prolonged therapy with T-20 induces emergence of T-20 resistant variants. In order to suppress the emergence of such resistant variants, we introduced charged and hydrophilic amino acids, glutamic acid (E) and lysine (K), at the solvent accessible site of C34. In particular, the modified peptide, SC34EK, demonstrates remarkably potent inhibition of membrane fusion by the resistant HIV-1 variants as well as wild-type viruses. The activity was specific to HIV-1 and little influenced by serum components. We found a strong correlation between the anti-HIV-1 activities of these peptides and the thermostabilities of the 6-helix bundles that are formed with these peptides. We also obtained the crystal structure of SC34EK in complex with a 36 amino acid sequence (N36) comprising the amino-terminal heptad repeat of HIV-1. The EK substitutions in the sequence of SC34EK were directed toward the solvent and generated an electrostatic potential, which may result in enhanced alpha-helicity of the peptide inhibitor. The 6-helix bundle complex of SC34EK with N36 appears to be structurally similar to that of C34 and N36. Our approach to enhancing alpha-helicity of the peptide inhibitor may enable future design of highly effective and specific HIV-1 inhibitors.     

Species‐dependent microarchitectural traits of iridescent scales in the triad taxa of Ornithoptera birdwing butterflies

Ornithoptera birdwing butterflies have blue, green, or orange iridescent scales in different species or subspecies. To understand the species‐ or subspecies‐dependent scale color differences, we performed comparative morphometric analyses of iridescent scales from three closely related taxa: O. priamus priamus (green), O. priamus urvillianus (blue), and O. croesus (orange). The three types of Ornithoptera wings exhibited reversible color changes to longer wavelengths with different kinetics upon immersion in methanol, suggesting that their color differences are at least partly based on differences in the size of air cavities made by nanostructures. Cover scales of all three color types were visually semi‐transparent glass scales that exhibited color when placed on a dark background. The dorsoventral differences in coloration were observed in single scales, suggesting the optical importance of scale surfaces. Scanning electron microscopy of cover scales in cross section revealed that all color types exhibited finely sculpted tapered ridges and thick, irregular basal multilayers containing tandemly clustered granular objects and air cavities. Scale thickness, ridge height, and multilayer thickness were significantly different among the three color types, and granular object size was significantly different between orange scales and blue and green scales. We conclude that each of the three taxa of Ornithoptera butterflies possesses unique quantitative size values on tapered ridges and irregular multilayers with granular objects and air cavities to express unique structural color. These species‐ or subspecies‐dependent structural colors might have evolved via quantitative shifts in these microarchitectural traits rather than via changes in the basic developmental or architectural plan for color expression.     

Transgenic rescue of Atg5-null mice from neonatal lethality with neuron-specific expression of ATG5: Systemic analysis of adult Atg5-deficient mice

Atg5-null mice are neonatal lethal. We have revealed in our recent paper that these mice die due to neuronal dysfunction resulting in suckling failure. Our new mouse model, atg5^–/–;Eno2/Nse-Atg5 mice, where Atg5 is deficient in the whole body except for neurons, enables us to analyze the consequences of macroautophagy/autophagy-deficiency in the whole body of adult mice.     

Mechanism of amyloid β-protein aggregation mediated by GM1 ganglioside clusters

It is widely accepted that the conversion of the soluble, nontoxic amyloid β-protein (Aβ) monomer to aggregated toxic Aβ rich in β-sheet structures is central to the development of Alzheimer's disease. However, the mechanism of the abnormal aggregation of Aβ in vivo is not well understood. We have proposed that ganglioside clusters in lipid rafts mediate the formation of amyloid fibrils by Aβ, the toxicity and physicochemical properties of which are different from those of amyloids formed in solution. In this paper, the mechanism by which Aβ-(1-40) fibrillizes in raftlike lipid bilayers composed of monosialoganglioside GM1, cholesterol, and sphingomyelin was investigated in detail on the basis of singular-value decomposition of circular dichroism data and analysis of fibrillization kinetics. At lower protein densities in the membrane (Aβ:GM1 ratio of less than ～0.013), only the helical species exists. At intermediate protein densities (Aβ:GM1 ratio between ～0.013 and ～0.044), the helical species and aggregated β-sheets (～15-mer) coexist. However, the β-structure is stable and does not form larger aggregates. At Aβ:GM1 ratios above ～0.044, the β-structure is converted to a second, seed-prone β-structure. The seed recruits monomers from the aqueous phase to form amyloid fibrils. These results will shed light on a molecular mechanism for the pathogenesis of the disease.     

Role of a tyrosine phosphorylation of SMG-9 in binding of SMG-9 to IQGAP and the NMD complex

SMG-9 is a component of the NMD complex, a heterotetramer that also includes SMG-1 and SMG-8 in the complex. SMG-9 was also originally identified as a tyrosine-phosphorylated protein but the role of the phosphorylation is not yet known. In this study, we determined that IQGAP protein, an actin cytoskeleton modifier acts as a binding partner with SMG-9 and this binding is regulated by phosphorylation of SMG-9 at Tyr-41. SMG-9 is co-localized with IQGAP1 as a part of the process of actin enrichment in non-stimulated cells, but not in the EGF-stimulated cells. Furthermore, an increase in the ability of SMG-9 to bind to SMG-8 occurs in response to EGF stimulation. These results suggest that tyrosine phosphorylation of SMG-9 may play a role in the formation of the NMD complex in the cells stimulated by the growth factor.     

Ecological consequences through responses of plant and soil communities to changing winter climate

Community processes are now undergoing substantial reconfiguration because of climate change. Although the effects of climate change on ecosystems are currently a major concern, the issues tightly associated with winter climate change have been underrepresented. Given the importance of winter climate variables and events for determining the spatial distribution of communities and their phenological and physiological responses, and the functional roles of each species, all of which are expected to substantially influence community dis/re-assemble in the future, this review focuses on the ecological responses and consequences of terrestrial communities to changing winter climate. In particular, the effects on processes supported by biological interactions are largely undetermined. In this context, focusing on plant–soil feedback as a major interactive multi-system is worthwhile; these interactions can be disentangled through careful evaluation of the functional roles of organisms involved in the feedback (i.e., plants and soil organisms). The underlying mechanisms are indeed complex because direct (i.e., changes in physical conditions) and indirect pathways (i.e., plant-mediated influences on soil-organisms and vice versa) from winter climate change influence the functionality of future ecosystems. To face these issues, the framework of response–effect-traits deserves research priority since this can define community re-organization as the accumulated responses of individual species, which determines the stability and performance of ecosystem functioning. Thus, research that quantifies functional responses and roles of organisms under a changing climate will continue to be essential for the issues of winter climate change, which may become more serious and significant in the near future.     

Characterization of mouse mediastinal fat-associated lymphoid clusters

The association between adipose tissue and immunity has been established and fat-associated lymphoid clusters (FALCs) are considered as a source of immune cells. We discovered lymphoid clusters (LCs) in mouse mediastinal fat tissues (MFTs). In Th1-biased C57BL/6N (B6), Th2-biased DBA/2Cr (DBA) and autoimmune-prone MRL/MpJ (MRL) mice strains, LCs without a fibrous capsule and germinal center were observed in white-colored MFTs extending from the diaphragm to the heart. The number and size of the LCs were larger in 12-month-old mice than in 3-month-old mice in all of the examined strains. Moreover, B6 had an especially large number of LCs compared with DBA and MRL. The immune cells in the LCs consisted of mainly T-cells and some B-cells. The majority of T-cells were CD4+ helper T (Th) cells, rather than CD8+ cytotoxic T-cells and no obvious immune cell population difference was present among the strains. Furthermore, high endothelial venules and lymphatic vessels in the LCs were better developed in B6 mice than in the other strains. Interestingly, some CD133+ hematopoietic progenitor cells and some c-Kit+/CD127+ natural helper cells were detected in the LCs. BrdU+ proliferating cells were more abundant in the LCs of B6 mice than in the LCs of the other strains and the number of BrdU+ cells increased with age. This is the first report of LCs in mouse MFTs. We suggest that the mouse genetic background affects LC size and number. We term the LCs “mediastinal fat-associated lymphoid clusters”. These clusters can be considered as niches for Th cell production.     

Infection of Adult Thymus with Murine Retrovirus Induces Virus-Specific Central Tolerance That Prevents Functional Memory CD8+ T Cell Differentiation

In chronic viral infections, persistent antigen presentation causes progressive exhaustion of virus-specific CD8⁺ T cells. It has become clear, however, that virus-specific naïve CD8⁺ T cells newly generated from the thymus can be primed with persisting antigens. In the setting of low antigen density and resolved inflammation, newly primed CD8⁺ T cells are preferentially recruited into the functional memory pool. Thus, continual recruitment of naïve CD8⁺ T cells from the thymus is important for preserving the population of functional memory CD8⁺ T cells in chronically infected animals. Friend virus (FV) is the pathogenic murine retrovirus that establishes chronic infection in adult mice, which is bolstered by the profound exhaustion of virus-specific CD8⁺ T cells induced during the early phase of infection. Here we show an additional evasion strategy in which FV disseminates efficiently into the thymus, ultimately leading to clonal deletion of thymocytes that are reactive to FV antigens. Owing to the resultant lack of virus-specific recent thymic emigrants, along with the above exhaustion of antigen-experienced peripheral CD8⁺ T cells, mice chronically infected with FV fail to establish a functional virus-specific CD8⁺ T cell pool, and are highly susceptible to challenge with tumor cells expressing FV-encoded antigen. However, FV-specific naïve CD8⁺ T cells generated in uninfected mice can be primed and differentiate into functional memory CD8⁺ T cells upon their transfer into chronically infected animals. These findings indicate that virus-induced central tolerance that develops during the chronic phase of infection accelerates the accumulation of dysfunctional memory CD8⁺ T cells.     

Cytokine and Nitric Oxide Levels in Patients with Sepsis – Temporal Evolvement and Relation to Platelet Mitochondrial Respiratory Function

Background

The levels of nitric oxide (NO) and various cytokines are known to be increased during sepsis. These signaling molecules could potentially act as regulators and underlie the enhancement of mitochondrial function described in the later phase of sepsis. Therefore, we investigated the correlation between observed changes in platelet mitochondrial respiration and a set of pro- and anti-inflammatory cytokines as well as NO plasma levels in patients with sepsis.

Methods and Results

Platelet mitochondrial respiration and levels of TNFα, MCP-1 (monocyte chemotactic protein-1), INFγ (interferon-γ), IL-1β, IL-4, IL-5, IL-6, IL-8, IL-10 and IL-17 and NO were analyzed in 38 patients with severe sepsis or septic shock at three time points during one week following admission to the ICU. Citrate synthase, mitochondrial DNA and cytochrome c were measured as markers of cellular mitochondrial content. All mitochondrial respiratory states increased over the week analyzed (p<0.001). IL-8 levels correlated with maximal mitochondrial respiration on day 6–7 (p = 0.02, r² = 0.22) and was also higher in non-survivors compared to survivors on day 3–4 and day 6–7 (p = 0.03 respectively). Neither NO nor any of the other cytokines measured correlated with respiration or mortality. Cytochrome c levels were decreased at day 1–2 by 24±5% (p = 0.03) and returned towards values of the controls at the last two time points. Citrate synthase activity and mitochondrial DNA levels were similar to controls and remained constant throughout the week.

Conclusions

Out of ten analyzed cytokines and nitric oxide, IL-8 correlated with the observed increase in mitochondrial respiration. This suggests that cytokines as well as NO do not play a prominent role in the regulation of platelet mitochondrial respiration in sepsis. Further, the respiratory increase was not accompanied by an increase in markers of mitochondrial content, suggesting a possible role for post-translational enhancement of mitochondrial respiration rather than augmented mitochondrial mass.     

Decreased miR-26a Expression Correlates with the Progression of Podocyte Injury in Autoimmune Glomerulonephritis

MicroRNAs contribute to the pathogenesis of certain diseases and may serve as biomarkers. We analyzed glomerular microRNA expression in B6.MRLc1, which serve as a mouse model of autoimmune glomerulonephritis. We found that miR-26a was the most abundantly expressed microRNA in the glomerulus of normal C57BL/6 and that its glomerular expression in B6.MRLc1 was significantly lower than that in C57BL/6. In mouse kidneys, podocytes mainly expressed miR-26a, and glomerular miR-26a expression in B6.MRLc1 mice correlated negatively with the urinary albumin levels and podocyte-specific gene expression. Puromycin-induced injury of immortalized mouse podocytes decreased miR-26a expression, perturbed the actin cytoskeleton, and increased the release of exosomes containing miR-26a. Although miR-26a expression increased with differentiation of immortalized mouse podocytes, silencing miR-26a decreased the expression of genes associated with the podocyte differentiation and formation of the cytoskeleton. In particular, the levels of vimentin and actin significantly decreased. In patients with lupus nephritis and IgA nephropathy, glomerular miR-26a levels were significantly lower than those of healthy controls. In B6.MRLc1 and patients with lupus nephritis, miR-26a levels in urinary exosomes were significantly higher compared with those for the respective healthy control. These data indicate that miR-26a regulates podocyte differentiation and cytoskeletal integrity, and its altered levels in glomerulus and urine may serve as a marker of injured podocytes in autoimmune glomerulonephritis.