The role of beta2 integrins and lipopolysaccharide-binding protein in the phagocytosis of dead Neisseria meningitidis

Phagocytosis of microbial pathogens is essential for the host immune response to infection. Our previous work has shown that lipooligosaccharide (LOS) expression on the surface of Neisseria meningitidis (Nm) is essential for phagocytosis, but the receptor involved remained unclear. In this study, we show that human CR3 (CD11b/CD18) and CR4 (CD11c/CD18) are phagocytic receptors for Nm as illustrated by the capacity of CR3- and CR4-transfected Chinese hamster ovary (CHO) cells to facilitate Nm uptake. A CR3-signalling mutant failed to internalize Nm, showing that the ability of CR3 to signal is essential for phagocytosis. Internalization of Nm by CR3-transfected CHO cells could be inhibited by the presence of CR3-specific antibodies. Furthermore, dendritic cells from leukocyte adhesion deficiency-1 patients, who have diminished expression of β2 integrins, showed markedly reduced phagocytosis of Nm. The CR3-mediated phagocytosis required the presence of lipopolysaccharide-binding protein (LBP). Furthermore, the expression of LOS by Nm was essential for LBP binding and phagocytosis via CR3. These results reveal a critical role of CR3 and LBP in the phagocytosis of Nm and provide important insights into the initial interaction meningococci have with the immune system.     

What makes pathogens pathogenic

Metazoans contain multiple complex microbial ecosystems in which the balance between host and microbe can be tipped from commensalism to pathogenicity. This transition is likely to depend both on the prevailing environmental conditions and on specific gene-gene interactions placed within the context of the entire ecosystem.     

Tissue specific expression of antifreeze protein and growth hormone transgenes driven by the ocean pout (<Emphasis Type="Italic">Macrozoarces americanus</Emphasis>) antifreeze protein OP5a gene promoter in Atlantic salmon (<Emphasis Type="Italic">Salmo salar</Emphasis>)

Previous research aimed at producing genetically improved salmon broodstock for aquaculture led to the creation of two lines of transgenic Atlantic salmon using gene constructs that were derived in part from the ocean pout OP5a antifreeze protein (AFP) gene. One of the lines was produced using an OP5a AFP gene in which the 5′ region of the promoter was removed (termed t-OP5a-AFP), and the other line contains a growth hormone (GH) transgene (EO-1α) that consists of a chinook salmon GH cDNA driven by a truncated OP5a AFP promoter that is almost identical to that of the t-OP5a-AFP construct. The similarity of the promoter regions of these transgenes provided an opportunity to evaluate their tissue specific expression patterns. Expression of mRNA was evaluated using Northern blot and RT-PCR techniques. The results demonstrate that the AFP and GH trangenes were expressed in almost all body tissues, suggesting that the promoter region of the OP5a AFP gene lacks tissue specific elements. Northern analysis revealed that expression of the t-OP5a-AFP gene was considerably greater than that of the EO-1α GH transgene. Only the spleen tissue of the GH transgenics showed a visible band of hybridization. In contrast clear bands of hybridization were evident in all tissues, except for blood cells, of the AFP transgenics with heart, liver and brain tissue showing the highest levels of mRNA expression. This higher level of expression could be attributable to the presence of introns in the t-OP5a-AFP transgene. Since the GH transgenic salmon grow considerably faster than non-transgenics the low levels of GH transgene expression in this line were clearly sufficient to produce the desired rapid growth phenotype. In contrast the levels of AFP expression were inadequate to impart any improvement in the freeze resistance of the AFP transgenic salmon.     

HIF-1 regulation: not so easy come, easy go

The hypoxia-inducible factor-1 (HIF-1) is the master regulator of the cellular response to hypoxia and its expression levels are tightly controlled through synthesis and degradation. It is widely accepted that HIF-1alpha protein accumulation during hypoxia results from inhibition of its oxygen-dependent degradation by the von Hippel Lindau protein (pVHL) pathway. However, recent data describe new pVHL- or oxygen-independent mechanisms for HIF-1alpha degradation. Furthermore, the hypoxia-induced increase in HIF-1alpha levels is facilitated by the continued translation of HIF-1alpha during hypoxia despite the global inhibition of protein translation. Recent work has contributed to an increased understanding of the mechanisms that control the translation and degradation of HIF-1alpha under both normoxic and hypoxic conditions.     

An altered pattern of circulating apolipoprotein E3 isoforms is implicated in preeclampsia

Preeclampsia is a common pregnancy complication that is an important cause of preterm birth and fetal growth restriction. Because there is no diagnostic test yet available for preeclampsia, we used a proteomic approach to identify novel serum/plasma biomarkers for this condition. We conducted case control studies comparing nulliparous women who developed preeclampsia at 36-38 weeks of gestation with healthy nulliparous women matched by gestational age at sampling. Serum/plasma was depleted of six abundant proteins and analyzed by two-dimensional gel electrophoresis (n = 12 per group) and difference gel electrophoresis (n = 12 per group). Differences in abundance of protein spots were detected by univariate and multivariate statistical analyses. Proteins were identified by mass spectrometry and expression of selected proteins was validated by immunoblotting. Proteins whose concentrations were selectively associated with preeclampsia included apolipoprotein E (apoE), apoC-II, complement factor C3c, fibrinogen, transthyretin, and complement factor H-related protein 2. An increase in a deglycosylated isoform of apoE3 and concomitantly decreased amounts of one apoE3 glycoisoform were identified in preeclamptic plasma and confirmed by immunoblotting. Altered production of these preeclampsia-related apoE3 isoforms might impair reverse cholesterol transport, contributing to arterial damage. These findings point to a novel mechanistic link between preeclampsia and subsequent cardiovascular disease.     

Cloning and expression of rabbit CCT subunits eta and beta in healing cutaneous wounds

We have previously identified the CCT subunit eta as specifically reduced in healing fetal skin wounds by differential display, and observed that this reduction is not seen with any other CCT subunit. We now report the cloning and characterization of the cDNAs for rabbit CCT-eta and its closest evolutionary homolog, CCT-beta. Quantitative examination of CCT-eta and –beta message expression in healing fetal and adult wounds at 12 h post-injury confirms that CCT-eta mRNA is decreased in fetal wound tissues, but actually elevated in adult wound tissues. CCT-beta mRNA, in contrast, remains unchanged in both fetal and adult wound tissues. CCT-eta mRNA remains persistently elevated in healing adult wounds for 28 days following injury, whereas CCT-beta mRNA remains invariant throughout. CCT-eta protein is similarly increased, whereas CCT-beta protein remains unchanged. -smooth muscle actin (-SMA), a recognized substrate of CCT known to be important in integumentary wound healing, was also measured over the course of wound healing, and both mRNA and protein levels were elevated throughout the 28 days.     

Testing hypotheses of Pleistocene population history using coalescent simulations: phylogeography of the pygmy nuthatch (Sitta pygmaea)

In this paper, we use mitochondrial NADH dehydrogenase subunit 2 sequences to test Pleistocene refugial hypotheses for the pygmy nuthatch (Sitta pygmaea). Pygmy nuthatches are a common resident of long-needle pine forests in western North America and demonstrate a particular affinity with ponderosa pine (Pinus ponderosa). Palaeoecological and genetic data indicate that ponderosa pine was isolated in two Pleistocene refugia corresponding to areas in the southern Sierra Nevada in the west and southern Arizona and New Mexico in the east. We use coalescent simulations to test the hypothesis that pygmy nuthatches tracked the Pleistocene history of their preferred habitat and persisted in two refugia during the periods of glacial maxima. Coalescent simulation of population history does not support the hypothesis of two Pleistocene refugia for the pygmy nuthatch. Instead, our data are consistent with a single refuge model. Nucleotide diversity is greatest in the western populations of southern and coastal California. We suggest that the pygmy nuthatch expanded from a far western glacial refuge into its current distribution since the most recent glacial maximum.