Rev-derived peptides inhibit HIV-1 replication by antagonism of Rev and a co-receptor,CXCR4

Rev, a viral regulatory protein of HIV-1, binds through its arginine-rich domain to the Rev-responsive element (RRE), a secondary structure in transcribed HIV-1 RNA. Binding of Rev to RRE mediates export of singly spliced or unspliced mRNAs from the nucleus to the cytoplasm. It has been previously shown that a certain arginine-rich peptide exhibits not only RRE-binding ability but also cell permeability and antagonism of CXCR4, one of the major coreceptors of HIV-1. Here we designed and synthesized arginine-rich peptides derived from the RNA-binding domain of Rev (Rev_34-50) and evaluated their anti-HIV-1 activities. Rev_34-50-A₄C, comprising Rev_34-50 with AAAAC at the C-terminus to increase the α-helicity, inhibited HIV-1 entry by CXCR4 antagonism and virus production in persistently HIV-1-infected PM1-CCR5 cells. Interestingly, similar motif of human lymphotropic virus type I Rex (Rex_1-21) also exerted moderate anti-HIV-1 activity. These results indicate that arginine-rich peptide, Rev_34-50-A₄C exerts dual antagonism against CXCR4 and Rev.     

Expression of the peptide hormone hepcidin increases in cardiomyocytes under myocarditis and myocardial infarction

The micronutrient iron is an essential component that plays a role in many crucial metabolic reactions. The peptide hormone hepcidin is thought to play a central role in iron homeostasis and its expression is induced by iron overloading and inflammation. Recently, hepcidin has been reported to be expressed also in the heart; however, the kinetics of altered hepcidin expression in diseases of the heart remain unknown. In this study, we examined cardiac expression of hepcidin in rat experimental autoimmune myocarditis (EAM), human myocarditis and rat acute myocardial infarction (AMI). In rat EAM and AMI hearts, hepcidin was expressed in cardiomyocytes; ferroportin, which is a cellular iron exporter bound by hepcidin, was also expressed in various cells. Analysis of the time course of the hepcidin to cytochrome oxidase subunit 6a (Cox6a)2 expression ratio showed that it abruptly increased more than 100-fold in hearts in the very early phase of EAM and in infarcted areas 1 day after MI. The hepcidin/Cox6a2 expression ratio correlated significantly with that of interleukin-6/γ-actin in both EAM and AMI hearts (r=0.781, P<.0001 and r=0.563, P=.0003). In human hearts with histological myocarditis, the ratio was significantly higher than in those without myocarditis (0.0400±0.0195 versus 0.0032±0.0017, P=.0045). Hepcidin is strongly induced in cardiomyocytes under myocarditis and MI, conditions in which inflammatory cytokine levels increase and may play an important role in iron homeostasis and free radical generation.     

NMR characterization of the interactions between lyso-GM1 aqueous micelles and amyloid β

Gangliosides are targets for a variety of pathologically relevant proteins, including amyloid β (Aβ), an important component implicated in Alzheimer’s disease (AD). To provide a structural basis for this pathogenic interaction associated with AD, we conducted NMR analyses of the Aβ interactions with gangliosides using lyso-GM1 micelles as a model system. Our NMR data revealed that the sugar-lipid interface is primarily perturbed upon binding of Aβ to the micelles, underscoring the importance of the inner part of the ganglioside cluster for accommodating Aβ in comparison with the outer carbohydrate branches that provide microbial toxin- and virus-binding sites.     

Should I stay or should I go? Hormonal control of nest abandonment in a long-lived bird, the Adélie penguin

According to life-history theory, long-lived birds should favor their survival over the current reproductive attempt, when breeding becomes too costly. In seabirds, incubation is often associated with spontaneous long-term fasting. Below a threshold in body reserves, hormonal and metabolic shift characteristics of a switch from lipid to protein utilization (phase III, PIII) occur. These metabolic changes are paralleled by nest abandonment and stimulation of refeeding behavior. Parental behavior is then under control of two hormones with opposite effects: corticosterone (CORT) and prolactin which stimulate foraging and incubation behavior, respectively.The aim of this study was to determine the respective role of these two hormones in nest abandonment by Adélie penguins. To this end, plasma hormone levels were measured before egg-laying and at departure from the colony (i.e. when birds were relieved by their partner or abandoned their nest), and related to nutritional state and incubation success.We found that males abandoning their nest in PIII presented high CORT levels and low prolactin levels. Interestingly, males which presented high plasma levels of prolactin in PIII did not abandon. We show that although CORT is the first hormone to be affected by prolonged energy constraints, the combined effects of high CORT and low prolactin levels are necessary for parents to favor self-maintenance and abandon the nest. We provide insights into time-course changes of the endocrine profile as PIII proceeds and report that reaching proteolytic late fasting is not sufficient to induce nest abandonment in a long-lived bird.     

Stimulation of the natural immune system in normal mice by polysaccharide from maitake mushroom

 Maitake D-Fraction is a polysaccharide extracted from the maitake mushroom (Grifola frondosa S.F. Gray). It is a β-glucan with a β-1,6 main chain with β-1,3 branches. Using normal C3H/Hej mice, its effects on the natural immune system, including macrophages, dendritic cells, and natural killer (NK) cells, were investigated. NK cells attack cells infected with pathogens such as bacteria and virus and produce cytokines, such as interferon-gamma (IFN-γ), that can modulate natural and specific immune responses. D-Fraction was administered to the mice intraperitoneally for 3 consecutive days; spleen cells containing macrophages and dendritic cells were then cultured and the culture supernatants were analyzed for IL-12. At the same time, IFN-γ expression in splenic NK cells was investigated. The levels of these cytokines were increased by D-Fraction. To elucidate NK cell activation by D-Fraction, CD69 expression on the surface of activated NK cells was examined, resulting in an increase in CD69-positive ratio for splenic NK cells. These results indicate that D-Fraction stimulates the natural immunity related to the activation of NK cells indirectly through IL-12 produced by macrophages and dendritic cells. Therefore, administration of D-Fraction to healthy individuals may serve to prevent infection. Received: August 1, 2002 / Accepted: February 10, 2003     

Talin, a host cell protein, interacts directly with the translocated intimin receptor, Tir, of enteropathogenic Escherichia coli, and is essential for pedestal formation

Enteropathogenic Escherichia coli (EPEC) is able to inject its own receptor, a transmembrane protein called translocated intimin receptor, Tir, into the host epithelial cell. The bacterium then uses an outer membrane protein, intimin, to bind to Tir and remains firmly attached to the host cell surface for the duration of the infection. The bacterium is also able to trigger the rearrangement of several host cell proteins, culminating with the formation of an actin-rich, pedestal-like structure beneath the EPEC adherence site. Although several cytoskeletal proteins are rearranged following EPEC infection, the exact role played by these proteins during pedestal formation remains unknown. We report here that talin, an integrin-binding protein, is recruited by EPEC and associates directly with Tir. By surface plasmon resonance (SPR), the predicted value for the dissociation constant ( K _D) for Tir–talin binding was 1.86 × 10⁻⁷ M. We also demonstrate that microinjection of anti-talin antibodies into HeLa cells resulted in the complete inability to focus actin filaments beneath the attached bacterium. These findings demonstrate that talin is essential for EPEC-induced pedestal formation in infected cells.     

Feeding strategies of free-ranging Adélie penguins Pygoscelis adeliae analysed by multiple data recording

The fine-scale feeding behaviour of free-ranging Adélie penguins (Pygoscelis adeliae) during a single foraging trip was investigated by monitoring three parameters simultaneously at a frequency of 1 Hz, these being depth, swim speed and oesophagus temperature. Ingestion events were detected as abrupt drops in the oesophageal temperature and related to the birds' foraging behaviour. Although a high percentage of oesophageal temperature loggers were rejected, 1 complete foraging trip was recorded for all the 3 parameters from 1 bird while 92% and 67% of the foraging trip was recorded for 2 other birds; 12.3% of the temperature drops occurred at the surface but they were mainly small, except 61 of them probably representing snow ingestion while the birds were on land. All other drops were observed during dives, 88% of them during the undulatory (and occasionally the ascent) phase of dives deeper than 40 m. The mean swim speed during non-feeding shallow and exploratory dives was relatively constant throughout the dive, around 2.1 m s^-1, whereas during feeding deep dives, swim speed during the undulatory phase was lower (1.71 m s^-1) than during the descent and ascent and was characterised by a series of rapid accelerations and decelerations; 42.6% of these accelerations were followed by one or more ingestion events and birds swam upward in 60% of the accelerations. Such multiple data recording opens new paths for the examination of the decision-making processes in foraging penguins.     

An N-ethyl-N-nitrosourea-induced mutation in N-acetyltransferase 1 in mice

Genetic variation in human N-acetyltransferases (NAT) has been implicated in susceptibility to aromatic amine and hydrazine carcinogens and therapeutic drugs. There are mouse models for variability of human NAT1; however mice with genetic differences in Nat1 (corresponding to human NAT2), have not been available. N-Ethyl-N-nitrosourea (ENU) mutagenesis was used to create genetic variation in Nat1. Among a number of mutations identified, a base-pair change substituting threonine for isoleucine at position 95 was recovered and studied. Molecular models suggested that this substitution would alter substrate binding. Analysis of hepatic Nat1 activity with the selective substrate isoniazid showed that there was a significant reduction in enzymatic activity in the homozygous mutants compared to the parental strain.