Infection-induced chromatin modifications facilitate translocation of herpes simplex virus capsids to the inner nuclear membrane

Herpes simplex virus capsids are assembled and packaged in the nucleus and move by diffusion through the nucleoplasm to the nuclear envelope for egress. Analyzing their motion provides conclusions not only on capsid transport but also on the properties of the nuclear environment during infection. We utilized live-cell imaging and single-particle tracking to characterize capsid motion relative to the host chromatin. The data indicate that as the chromatin was marginalized toward the nuclear envelope it presented a restrictive barrier to the capsids. However, later in infection this barrier became more permissive and the probability of capsids to enter the chromatin increased. Thus, although chromatin marginalization initially restricted capsid transport to the nuclear envelope, a structural reorganization of the chromatin counteracted that to promote capsid transport later. Analyses of capsid motion revealed that it was subdiffusive, and that the diffusion coefficients were lower in the chromatin than in regions lacking chromatin. In addition, the diffusion coefficient in both regions increased during infection. Throughout the infection, the capsids were never enriched at the nuclear envelope, which suggests that instead of nuclear export the transport through the chromatin is the rate-limiting step for the nuclear egress of capsids. This provides motivation for further studies by validating the importance of intranuclear transport to the life cycle of HSV-1.     

A short-lived herbivore on a long-lived host: tree resistance to herbivory depends on leaf age

Short-lived insect herbivores should be able to adapt to the resistance mechanisms of their long-lived woody hosts because the life span of a single host will encompass numerous generations of herbivores. However, adaptation may be slowed down if host genotypes can create, in a single genotype, such large phenotypic variation in traits relevant for the herbivore that it matches variance among host genotypes. We tested this hypothesis by measuring leaf consumption by, and growth of, half-sibs of the geometrid moth Epirrita autumnata on individual birch trees, during three instars. The instar×tree interaction, rather than tree identity alone, was a significant variance component for both consumption and growth, indicating that different larval instars ranked individual trees differently. Both consumption and growth varied most between the 3rd and the later (4th and 5th) instars, coinciding with rapid seasonal changes in numerous nutritive and phenolic traits of maturing leaves. Thus, developmental variance in the leaf quality of individual trees may reduce the likelihood of E. autumnata genotypes adapting to the defenses of their host trees. We did not find evidence of in the ability of different half-sibs to utilize individual trees or leaf stages, indicating that E. autumnata larvae are generalists over a wide variety of host traits.     

Insulin‐ and Exercise‐Stimulated Skeletal Muscle Blood Flow and Glucose Uptake in Obese Men

Objective: Insulin resistance in obese subjects results in the impaired use of glucose by insulin‐sensitive tissues, e.g., skeletal muscle. In the present study, we determined whether insulin resistance in obesity is associated with an impaired ability of exercise to stimulate muscle blood flow, oxygen delivery, or glucose uptake. Research Methods and Procedures: Nine obese (body mass index = 36 ± 2 kg/m²) and 11 age‐matched nonobese men (body mass index = 22 ± 1 kg/m²) performed one‐legged isometric exercise during hyperinsulinemia. Rates of femoral muscle blood flow, oxygen consumption, and glucose uptake were measured simultaneously in both legs using [¹⁵O]H₂O, [¹⁵O]O₂, [¹⁸F]fluoro‐deoxy‐glucose, and positron emission tomography. Results: The obese subjects exhibited resistance to insulin stimulation of glucose uptake in resting muscle, regardless of whether glucose uptake was expressed per kilogram of femoral muscle mass (p = 0.001) or per the total mass of quadriceps femoris muscle. At similar workloads, oxygen consumption, blood flow, and glucose uptake were lower in the obese than the nonobese subjects when expressed per kilogram of muscle, but similar when expressed per quadriceps femoris muscle mass. Discussion: We conclude that obesity is characterized by insulin resistance of glucose uptake in resting skeletal muscle regardless of how glucose uptake is expressed. When compared with nonobese individuals at similar absolute workloads and under identical hyperinsulinemic conditions, the ability of exercise to increase muscle oxygen uptake, blood flow, and glucose uptake per muscle mass is blunted in obese insulin‐resistant subjects. However, these defects are compensated for by an increase in muscle mass.     

The OSBP-related proteins: a novel protein family involved in vesicle transport,cellular lipid metabolism,and cell signalling

Proteins/genes showing high sequence homology to the mammalian oxysterol binding protein (OSBP) have been identified in a variety of eukaryotic organisms from yeast to man. The unifying feature of the gene products denoted as OSBP-related proteins (ORPs) is the presence of an OSBP-type ligand binding (LB) domain. The LB domains of OSBP and its closest homologue bind oxysterols, while data on certain other family members suggest interaction with phospholipids. Many ORPs also have a pleckstrin homology (PH) domain in the amino-terminal region. The PH domains of the family members studied in detail are known to interact with membrane phosphoinositides and play an important role in the intracellular targeting of the proteins. It is plausible that the ORPs constitute a regulatory apparatus that senses the status of specific lipid ligands in membranes, using the PH and/or LB domains, and mediates information to yet poorly known downstream machineries. Functional studies carried out on the ORP proteins in different organisms indicate roles of the gene family in diverse cellular processes including control of lipid metabolism, regulation of vesicle transport, and cell signalling events.     

Lumbo-sacral neural crest derivatives fate mapped with the aid of Wnt-1 promoter integrate but are not essential to kidney development

Neural crest (NC) cells may be involved in kidney organogenesis by providing inductive signals and contributing to cells of the renal stroma. We show here that the lumbo-sacral NC cells fate mapped with the aid of Wnt-1 promoter in the mouse migrate close to the metanephros at the initiation of organogenesis but these cells remain superficial to the condensed Pax2-expressing mesenchymal cells. NC-derived cells enter later into the kidney proper from the midline region. The NC cells contribute also to development of the extra-adrenal para-aortic bodies, Zuckerkandl's bodies and the nerve cord of the sympathetic nervous system. Splotch (Sp^2H/Sp^2H) embryos, having a NC defect in the lumbo-sacral region, develop a normal metanephros even though the kidney does not express the NC markers Sox10, Phox2b and tyrosine hydroxylase. Consistent with the histological findings, the kidneys of Sp^2H/Sp^2H embryos also express the stromal genes Foxd1, Hoxa10 and RARβ normally. Wnt-1 promoter-marked wild-type LacZ NC cells migrate intensely from the heterologous inducer tissue of the embryonic dorsal spinal cord (SPC) to the kidney mesenchyme, but tubule induction does not depend on NC migration, since the Sp^2H/Sp^2H SPC also induces tubulogenesis. The Sp^2H/Sp^2H mesenchyme also remains competent for tubulogenesis. We conclude that the NC cells fate mapped with the aid of Wnt-1 promoter migrate to the close to the metanephros and form later derivatives integrating with the kidney, but they may not be essential to the development of the stromal cells nor they may provide critical morphogenetic signals to regulate early kidney development in vivo.     

Absence of TGFβ signaling in embryonic vascular smooth muscle leads to reduced lysyl oxidase expression,impaired elastogenesis,and aneurysm

To address the requirement for TGFβ signaling in the formation and maintenance of the vascular matrix, we employed lineage‐specific mutation of the type II TGFβ receptor gene (Tgfbr2) in vascular smooth muscle precursors in mice. In both neural crest‐ and mesoderm‐derived smooth muscle, absence of TGFβ receptor function resulted in a poorly organized vascular elastic matrix in late‐stage embryos which was prone to dilation and aneurysm. This defect represents a failure to initiate formation of the elastic matrix, rather than a failure to maintain a preexisting matrix. In mutant tissue, lysyl oxidase expression was substantially reduced, which may contribute to the observed pathology. genesis 47:115–121, 2009. © 2009 Wiley‐Liss, Inc.     

1H, 13C and 15N resonance assignments of the major extracytoplasmic domain of the cell shape-determining protein MreC from Bacillus subtilis

MreB, MreC and MreD are essential cell shape-determining morphogenetic proteins in Gram-positive and in Gram-negative bacteria. While MreB, the bacterial homologue of the eukaryotic cytoskeletal protein actin, has been extensively studied, the roles of MreC and MreD are less well understood. They both are transmembrane proteins. MreC has a predicted single transmembrane domain and the C-terminal part outside the cell membrane. MreC probably functions as a link between the intracellular cytoskeleton and the cell wall synthesizing machinery which is located at the outer surface of the cell membrane. Also proteins involved in cell wall synthesis participate in cell morphogenesis. How these two processes are coordinated is, however, poorly understood. Bacillus subtilis (BS), a non-pathogenic Gram-positive bacterium, is widely used as a model for Gram-positive pathogens, e.g. Staphylococcus aureus (SA). Currently, the structures of MreC from BS and SA are not known. As part of our efforts to elucidate the structure–function relationships of the morphogenetic protein complexes in Gram-positive bacteria, we present the backbone and side chain resonance assignments of the extracytoplasmic domain of MreC from BS.     

Inactivation of the Ecs ABC transporter of Staphylococcus aureus attenuates virulence by altering composition and function of bacterial wall

Background

Ecs is an ATP-binding cassette (ABC) transporter present in aerobic and facultative anaerobic Gram-positive Firmicutes. Inactivation of Bacillus subtilis Ecs causes pleiotropic changes in the bacterial phenotype including inhibition of intramembrane proteolysis. The molecule(s) transported by Ecs is (are) still unknown.

Methodology/Principal Findings

In this study we mutated the ecsAB operon in two Staphylococcus aureus strains, Newman and LS-1. Phenotypic and functional characterization of these Ecs deficient mutants revealed a defect in growth, increased autolysis and lysostaphin sensitivity, altered composition of cell wall proteins including the precursor form of staphylokinase and an altered bacterial surface texture. DNA microarray analysis indicated that the Ecs deficiency changed expression of the virulence factor regulator protein Rot accompanied by differential expression of membrane transport proteins, particularly ABC transporters and phosphate-specific transport systems, protein A, adhesins and capsular polysaccharide biosynthesis proteins. Virulence of the ecs mutants was studied in a mouse model of hematogenous S. aureus infection. Mice inoculated with the ecs mutant strains developed markedly milder infections than those inoculated with the wild-type strains and had consequently lower mortality, less weight loss, milder arthritis and decreased persistence of staphylococci in the kidneys. The ecs mutants had higher susceptibility to ribosomal antibiotics and plant alkaloids chelerythrine and sanguinarine.

Conclusions/Significance

Our results show that Ecs is essential for staphylococcal virulence and antimicrobial resistance probably since the transport function of Ecs is essential for the normal structure and function of the cell wall. Thus targeting Ecs may be a new approach in combating staphylococcal infection.