Tumor-reactive CD4+ T cell responses to the melanoma-associated chondroitin sulphate proteoglycan in melanoma patients and healthy individuals in the absence of autoimmunity

To avoid immune escape by down-regulation or loss of Ag by the tumor cells, target Ags are needed, which are important for the malignant phenotype and survival of the tumor. We could identify a CD4(+) T cell epitope derived from the human melanoma-associated chondroitin sulfate proteoglycan (MCSP) (also known as high m.w.-melanoma-associated Ag), which is strongly expressed on >90% of human melanoma lesions and is important for the motility and invasion of melanoma cells. However, MCSP is not strictly tumor specific, because it is also expressed in a variety of normal tissues. Therefore, self tolerance should prevent the induction of strong T cell responses against these Ags by vaccination strategies. In contrast, breaking self tolerance to this Ag by effectively manipulating the immune system might mediate antitumor responses, although it would bear the risk of autoimmunity. Surprisingly, we could readily isolate CD4(+) Th cells from the blood of a healthy donor-recognizing peptide MCSP(693-709) on HLA-DR11-expressing melanoma cells. Broad T cell reactivity against this Ag could be detected in the peripheral blood of both healthy donors and melanoma patients, without any apparent signs of autoimmune disease. In some patients, a decline of T cell reactivity was observed upon tumor progression. Our data indicate that CD4(+) T cells are capable of recognizing a membrane glycoprotein that is important in melanoma cell function, and it may be possible that the sizable reactivity to this Ag in most normal individuals contributes to immune surveillance against cancer.     

Gliadin regulates the NK-dendritic cell cross-talk by HLA-E surface stabilization

We analyzed the autologous NK cell interaction with gliadin-presenting dendritic cells. Gliadin is the known Ag priming the celiac disease (CD) pathogenesis. We demonstrate that gliadin prevents immature dendritic cells (iDCs) elimination by NK cells. Furthermore, cooperation between human NK cells-iDCs and T cells increases IFN-gamma production of anti-gliadin immune response. Gliadin fractions were analyzed for their capability to stabilize HLA-E molecules. The alpha and omega fractions conferred the protection from NK cell lysis to iDCs and increased their HLA-E expression. Gliadin pancreatic enzyme digest and a peptide derived from gliadin alpha increased HLA-E levels on murine RMA-S/HLA-E-transfected cells. Analysis of HLA-E expression in the small intestinal mucosa of gluten-containing diet celiac patients and organ culture experiments confirmed the in vitro data.     

The Akt/GSK-3beta axis as a new signaling pathway of the histamine H(3) receptor

Drugs targeting the histamine H(3) receptor (H(3)R) are suggested to be beneficial for the treatment of neurodegenerative diseases, such as Alzheimer's and Parkinson's disease. The H(3)R activates G(i/o)-proteins to inhibit adenylyl cyclase activity and modulates phospholipase A(2) and MAPK activity. Herein we show that, in transfected SK-N-MC cells, the H(3)R modulates the activity of the Akt/Glycogen synthase kinase 3beta (GSK-3beta) axis both in a constitutive and agonist-dependent fashion. H(3)R stimulation with the H(3)R agonist immepip induces the phosphorylation of both Ser473 and Thr308 on Akt, a serine/threonine kinase that is important for neuronal development and function. The H(3)R-mediated activation of Akt can be inhibited by the H(3)R inverse agonist thioperamide, and by Wortmannin, LY294002 and PTX, suggesting the observed Akt activation occurs via a G(i/o)-mediated activation of phosphoinositide-3-kinase. H(3)R activation also results in the phosphorylation of Ser9 on GSK-3beta, which acts downstream of Akt and has a prominent role in brain function. In addition, we show the H(3)R-mediated phosphorylation of Akt at Ser473 to occur in primary rat cortical neurons and in rat brain slices. The discovery of this signaling property of the H(3)R adds new understanding to the roles of histamine and the H(3)R in brain function and pathology.     

Binding of human plasminogen to Bifidobacterium

Bifidobacteria constitute up to 3% of the total microbiota and represent one of the most important health-promoting bacterial groups of the human intestinal microflora. The presence of Bifidobacterium in the human gastrointestinal tract has been directly related to several health-promoting activities; however, to date, no information about the specific mechanisms of interaction with the host is available. In order to provide some insight into the molecular mechanisms involved in the interaction with the host, we investigated whether Bifidobacterium was able to capture human plasminogen on the cell surface. By using flow cytometry, we demonstrated a dose-dependent human plasminogen-binding activity for four strains belonging to three bifidobacterial species: Bifidobacterium lactis, B. bifidum, and B. longum. The binding of human plasminogen to Bifidobacterium was dependent on lysine residues of surface protein receptors. By using a proteomic approach, we identified five putative plasminogen-binding proteins in the cell wall fraction of the model strain B. lactis BI07. The data suggest that plasminogen binding to B. lactis is due to the concerted action of a number of proteins located on the bacterial cell surface, some of which are highly conserved cytoplasmic proteins which have other essential cellular functions. Our findings represent a step forward in understanding the mechanisms involved in the Bifidobacterium-host interaction.     

Global phylogenetic structure of the hyperdiverse ant genus Pheidole reveals the repeated evolution of macroecological patterns

Adaptive radiations are of particular interest owing to what they reveal about the ecological and evolutionary regulation of biodiversity. This applies to localized island radiations such as Darwin''s finches, and also to rapid radiations occurring on a global scale. Here we analyse the macroevolution and macroecology of Pheidole, a famously hyperdiverse and ecologically dominant ant genus. We generate and analyse four novel datasets: (i) a robust global phylogeny including 285 Pheidole species, (ii) a global database on regional Pheidole richness in 365 political areas summarizing over 97 000 individual records from more than 6500 studies, (iii) a global database of Pheidole richness from 3796 local communities and (iv) a database of Pheidole body sizes across species. Analysis of the potential climate drivers of richness revealed that the patterns are statistically very similar across different biogeographic regions, with both regional and local richness associated with the same coefficients of temperature and precipitation. This similarity occurs even though phylogenetic analysis shows that Pheidole reached dominance in communities through serial localized radiations into different biomes within different continents and islands. Pheidole body size distributions have likewise converged across geographical regions. We propose these cases of convergence indicate that the global radiation of Pheidole is structured by deterministic factors regulating diversification and diversity.     

Molecular dynamics simulation of deoxy and carboxy murine neuroglobin in water

Globins are respiratory proteins that reversibly bind dioxygen and other small ligands at the iron of a heme prosthetic group. Hemoglobin and myoglobin are the most prominent members of this protein family. Unexpectedly a few years ago a new member was discovered and called neuroglobin (Ngb), being predominantly expressed in the brain. Ngb is a single polypeptide of 151 amino acids and despite the small sequence similarity with other globins, it displays the typical globin fold. Oxygen, nitric oxide, or carbon monoxide can displace the distal histidine which, in ferrous Ngb as well as in ferric Ngb, is bound to the iron, yielding a reversible adduct. Recent crystallographic data on carboxy Ngb show that binding of an exogenous ligand is associated to structural changes involving heme sliding and a topological reorganization of the internal cavities; in particular, the huge internal tunnel that connects the bulk with the active site, peculiar to Ngb, is heavily reorganized. We report the results of extended (90 ns) molecular dynamics simulations in water of ferrous deoxy and carboxy murine neuroglobin, which are both coordinated on the distal site, in the latter case by CO and in the former one by the distal His(64)(E7). The long timescale of the simulations allowed us to characterize the equilibrated protein dynamics and to compare protein structure and dynamical behavior coupled to the binding of an exogenous ligand. We have characterized the heme sliding motion, the topological reorganization of the internal cavities, the dynamics of the distal histidine, and particularly the conformational change of the CD loop, whose flexibility depends ligand binding.     

A facile Er(OTf)3-catalyzed synthesis of 2,3-unsaturated O- and S-glycosides

Er(OTf)(3) is a useful catalyst for the Ferrier rearrangement furnishing high yields of O- and S-glycosides. The transformation has wide applicability, cleaner reaction profiles, mild reaction conditions, and high stereoselectivity and the catalyst, which is also commercially available, can be recovered and reused.