Homophilic adhesion and CEACAM1-S regulate dimerization of CEACAM1-L and recruitment of SHP-2 and c-Src

Carcinoembryonic antigen (CEA)–related cell adhesion molecule 1 (CAM1 [CEACAM1]) mediates homophilic cell adhesion and regulates signaling. Although there is evidence that CEACAM1 binds and activates SHP-1, SHP-2, and c-Src, knowledge about the mechanism of transmembrane signaling is lacking. To analyze the regulation of SHP-1/SHP-2/c-Src binding, we expressed various CFP/YFP-tagged CEACAM1 isoforms in epithelial cells. The supramolecular organization of CEACAM1 was examined by cross-linking, coclustering, coimmunoprecipitation, and fluorescence resonance energy transfer. SHP-1/SHP-2/c-Src binding was monitored by coimmunoprecipitation and phosphotyrosine-induced recruitment to CEACAM1-L in cellular monolayers. We find that trans-homophilic CEACAM1 binding induces cis-dimerization by an allosteric mechanism transmitted by the N-terminal immunoglobulin-like domain. The balance of SHP-2 and c-Src binding is dependent on the monomer/dimer equilibrium of CEACAM1-L and is regulated by trans-binding, whereas SHP-1 does not bind under physiological conditions. CEACAM1-L homodimer formation is reduced by coexpression of CEACAM1-S and modulated by antibody ligation. These data suggest that transmembrane signaling by CEACAM1 operates by alteration of the monomer/dimer equilibrium, which leads to changes in the SHP-2/c-Src–binding ratio.     

Lipid composition of brain myelin from normal and hyperphenylalaninemic chick embryos

The influence of hyperphenylalaninemia on the lipid composition of brain myelin has been investigated in 19-day-old chick embryos. CNP-ase activity was used as myelin marker enzyme for myelin isolation. CNP-ase activity was significantly lower in hyperphenylalaninemic myelin when compared with control. No significant differences were observed after experimental treatment in the total lipid content of myelin as well as in the proportion of cholesterol:phospholipid:galactolipid. Nevertheless, a clear increase in the percentage of esterified cholesterol was found. No appreciable alterations were observed in the phospholipid composition of brain myelin from both control and hyperphenylalaninemic chick embryos. However, the ratio of unsaturated to saturated fatty acids in serine plasmalogen and sphingomyelin was considerably increased by this treatment. This ratio in choline and ethanolamine phosphatides from treated embryos did not differ from that of controls.     

The sensory modality used for learning affects grades

Second-year undergraduated students from 2008, 2009, and 2010 cohorts were asked to respond a questionnaire to determine their learning style preferences, the VARK questionnaire (where V is visual, A is aural, R is reading-writing, and K is kinesthetic), which was translated into Spanish by the author. The translated questionnaire was tested for wording comprehension before its application in the actual study. Using the results of the VARK questionnaire, students were classified as unimodal or multimodal and according to the first preferred sensory modality used for learning as V, A, R, or K learners. Multiple-choice questions (MCQs) and problems that required simple arithmetic calculations (arithmetic-type questions) were applied to the students. The relation between the main sensory modality used for learning and the grades obtained in each question type was analyzed both in unimodal and multimodal students. It was found that R unimodal students performed significantly better in arithmetic questions than A and K unimodal students (P < 0.001 by a Bonferroni multiple-comparison test after ANOVA). R unimodal students also performed better than R multimodal students in arithmetic questions (P = 0.02 by a Mann-Whitney U-test). However, no differences were observed after MCQs in either unimodal or multimodal students with different first sensory modalities used for learning. When MCQ scores between unimodal and multimodal students were compared, no differences were detected. It was concluded that the sensory learning style used for learning affects student outcome when students receive arithmetic questions but not when MCQs are applied.     

The styryl dye FM1-43 suppresses odorant responses in a subset of olfactory neurons by blocking cyclic nucleotide-gated (CNG) channels

Many olfactory receptor neurons use a cAMP-dependent transduction mechanism to transduce odorants into depolarizations. This signaling cascade is characterized by a sequence of two currents: a cation current through cyclic nucleotide-gated channels followed by a chloride current through calcium-activated chloride channels. To date, it is not possible to interfere with these generator channels under physiological conditions with potent and specific blockers. In this study we identified the styryl dye FM1-43 as a potent blocker of native olfactory cyclic nucleotide-gated channels. Furthermore, we characterized this substance to stain olfactory receptor neurons that are endowed with cAMP-dependent transduction. This allows optical differentiation and pharmacological interference with olfactory receptor neurons at the level of the signal transduction.     

Comparison of PCR protocols for detecting Histoplasma capsulatum DNA through a multicenter study

BackgroundA multicenter study was conducted. A panel containing DNA from Histoplasma capsulatum, as well as negative and cross-reaction controls, was sent to five different laboratories, members of the MICOMOL network from CYTED Program.AimsThe objective was to assess the accuracy of different PCR protocols to detect H. capsulatum DNA.MethodsSeven different PCR protocols were tested. They were based on PCR techniques and used unicopy and multicopy targets.ResultsMost of these protocols (4/7) were able to detect the smallest amounts of fungal DNA (10² fg/μl). Overall sensitivity was 86% and specificity was 100%. The protocol based on a unicopy target (SCAR₂₂₀) presented lower sensitivity (43%) but 100% specificity. The real-time protocols tested were highly reproducible, sensitive, and specific. Neither false positives nor cross-reactions were detected in any protocol.ConclusionsAll laboratories were able to amplify H. capsulatum DNA, and real-time PCR seems to be a promising tool to efficiently detect this pathogen in clinical samples.     

REPRODUCTIVE BIOLOGY OF A TROPICAL PALM SWAMP COMMUNITY IN THE VENEZUELAN LLANOS

The reproductive biology of a tropical palm swamp community, called morichal in the Venezuelan Central Llanos, was studied. Of the 128 woody and herbaceous species of plants recorded, 99 (77.34%) were hermaphrodites, 25 (19.53%) were monoecious, and four (3.13%) were dioecious. The morichal is characterized by a low number of species with obligate cross-fertilization. The frequencies of species with different breeding systems in a subsample of 26 species showed that eight (30.77%) were self-incompatible, 14 (53.85%) were self-compatible, and four (15.38%) were agamospermous. Ten of 14 self-compatible species were autogamous. Regardless of the self-incompatibility level estimated, seed and fruit set were greater in self-fertilized flowers than in hand-pollinated flowers in three of the nine self-incompatible species. These results are related to the facts that: 1) the relative isolation of the plant population limits the gene flow among similar communities and enforces the intrapopulation pollen flow; 2) the overlapping flowering patterns and infrequent and unspecialized pollinators may be enforcing self-compatibility and agamospermy; 3) self-compatibility is the rule among short-lived species in the morichal; and 4) three out of four agamospermous species are of the Melastomataceae family.     

Interferon-Inducible Mechanism of Dendritic Cell-Mediated HIV-1 Dissemination Is Dependent on Siglec-1/CD169

Human immunodeficiency virus type 1 (HIV-1) interactions with myeloid dendritic cells (DCs) can result in virus dissemination to CD4⁺ T cells via a trans infection pathway dependent on virion incorporation of the host cell derived glycosphingolipid (GSL), GM3. The mechanism of DC-mediated trans infection is extremely efficacious and can result in infection of multiple CD4⁺ T cells as these cells make exploratory contacts on the DC surface. While it has long been appreciated that activation of DCs with ligands that induce type I IFN signaling pathway dramatically enhances DC-mediated T cell trans infection, the mechanism by which this occurs has remained unclear until now. Here, we demonstrate that the type I IFN-inducible Siglec-1, CD169, is the DC receptor that captures HIV in a GM3-dependent manner. Selective downregulation of CD169 expression, neutralizing CD169 function, or depletion of GSLs from virions, abrogated DC-mediated HIV-1 capture and trans infection, while exogenous expression of CD169 in receptor-naïve cells rescued GSL-dependent capture and trans infection. HIV-1 particles co-localized with CD169 on DC surface immediately following capture and subsequently within non-lysosomal compartments that redistributed to the DC – T cell infectious synapses upon initiation of T cell contact. Together, these findings describe a novel mechanism of pathogen parasitization of host encoded cellular recognition machinery (GM3 – CD169 interaction) for DC-dependent HIV dissemination.