Ntann12 annexin expression is induced by auxin in tobacco roots

Ntann12, encoding a polypeptide homologous to annexins, was found previously to be induced upon infection of tobacco with the bacterium Rhodococcus fascians. In this study, Ntann12 is shown to bind negatively charged phospholipids in a Ca(2+)-dependent manner. In plants growing in light conditions, Ntann12 is principally expressed in roots and the corresponding protein was mainly immunolocalized in the nucleus. Ntann12 expression was inhibited following plant transfer to darkness and in plants lacking the aerial part. However, an auxin (indole-3-acetic acid) treatment restored the expression of Ntann12 in the root system in dark conditions. Conversely, polar auxin transport inhibitors such as 1-naphthylphthalamic acid (NPA) or 2,3,5-triiodobenzoic acid (TIBA) inhibited Ntann12 expression in light condition. These results indicate that the expression of Ntann12 in the root is linked to the perception of a signal in the aerial part of the plant that is transmitted to the root via polar auxin transport.     

Different expression levels of the TAP peptide transporter lead to recognition of different antigenic peptides by tumor-specific CTL

Decreased antigenicity of cancer cells is a major problem in tumor immunology. This is often acquired by an expression defect in the TAP. However, it has been reported that certain murine Ags appear on the target cell surface upon impairment of TAP expression. In this study, we identified a human CTL epitope belonging to this Ag category. This epitope is derived from preprocalcitonin (ppCT) signal peptide and is generated within the endoplasmic reticulum by signal peptidase and signal peptide peptidase. Lung cancer cells bearing this antigenic peptide displayed low levels of TAP, but restoration of their expression by IFN-γ treatment or TAP1 and TAP2 gene transfer abrogated ppCT Ag presentation. In contrast, TAP upregulation in the same tumor cells increased their recognition by proteasome/TAP-dependent peptide-specific CTLs. Thus, to our knowledge, ppCT(16-25) is the first human tumor epitope whose surface expression requires loss or downregulation of TAP. Lung tumors frequently display low levels of TAP molecules and might thus be ignored by the immune system. Our results suggest that emerging signal peptidase-generated peptides represent alternative T cell targets, which permit CTLs to destroy TAP-impaired tumors and thus overcome tumor escape from CD8(+) T cell immunity.     

Uncoupling charge movement from channel opening in voltage-gated potassium channels by ruthenium complexes

The Kv2.1 channel generates a delayed-rectifier current in neurons and is responsible for modulation of neuronal spike frequency and membrane repolarization in pancreatic β-cells and cardiomyocytes. As with other tetrameric voltage-activated K(+)-channels, it has been proposed that each of the four Kv2.1 voltage-sensing domains activates independently upon depolarization, leading to a final concerted transition that causes channel opening. The mechanism by which voltage-sensor activation is coupled to the gating of the pore is still not understood. Here we show that the carbon-monoxide releasing molecule 2 (CORM-2) is an allosteric inhibitor of the Kv2.1 channel and that its inhibitory properties derive from the CORM-2 ability to largely reduce the voltage dependence of the opening transition, uncoupling voltage-sensor activation from the concerted opening transition. We additionally demonstrate that CORM-2 modulates Shaker K(+)-channels in a similar manner. Our data suggest that the mechanism of inhibition by CORM-2 may be common to voltage-activated channels and that this compound should be a useful tool for understanding the mechanisms of electromechanical coupling.     

Evidence for non-disomic inheritance in a Citrus interspecific tetraploid somatic hybrid between C. reticulata and C. limon using SSR markers and cytogenetic analysis

Artificial tetraploid somatic hybrids have been developed for sterile triploid citrus breeding by sexual hybridization between diploid and tetraploid somatic hybrids. The genetic structure of diploid gametes produced by tetraploid genotypes depends on the mode of chromosome association at meiosis. In order to evaluate tetraploid inheritance in a tetraploid interspecific somatic hybrid between mandarin and lemon, we performed segregation studies using cytogenetic and single sequence repeat molecular markers. Cytogenetic analysis of meiosis in the somatic hybrid revealed 11% tetravalents and 76% bivalents. Inheritance of the tetraploid hybrid was analyzed by genotyping the triploid progeny derived from a cross between a diploid pummelo and the tetraploid somatic hybrid, in order to derive genotypes of the meiospores produced by the tetraploid. A likelihood-based approach was used to distinguish between disomic, tetrasomic, and intermediate inheritance models and to estimate the double reduction rate. In agreement with expectations based the cytogenetic data, marker segregation was largely compatible with tetrasomic and inheritance intermediate between disomic and tetrasomic, with some evidence for preferential pairing of homoeologous chromosomes. This has important implications for the design of breeding programs that involve tetraploid hybrids, and underscores the need to consider inheritance models that are intermediate between disomic and tetrasomic.     

Discoidin domain receptor 1 expression in activated T cells is regulated by the ERK MAP kinase signaling pathway

The expression and function of discoidin domain receptor 1 (DDR1) in T cells are still poorly explored. We have recently shown that activation of primary human T cells via their T cell receptor leads to increased expression of DDR1, which promoted their migration in three-dimensional collagen. In the present study, we provide evidence that activated T cells bind collagen through DDR1. We found that the DDR1:Fc blocking molecule significantly reduced the ability of activated T cells to bind soluble biotinylated collagen. However, DDR1:Fc had no impact on the adhesion of activated T cells to collagen and overexpression of DDR1 in Jurkat T cells did not enhance their adhesion. Together, our results indicate that DDR1 can promote T cell migration without enhancing adhesion to collagen, suggesting that it can contribute to the previously described amoeboid movement of activated T cells in collagen matrices. Our results also show that CD28, in contrast to IL-2 expression, did not costimulate the expression of DDR1 in primary human T cells. Using specific inhibitors, we demonstrated that TCR-induced expression of DDR1 in T cells is regulated by the Ras/Raf/ERK MAP Kinase and PKC pathways but not by calcium/calcineurin signaling pathway or the JNK and P38 MAP Kinases. Thus, our study provides additional insights into the physiology of DDR1 in T cells and may therefore further our understanding of the regulatory mechanisms of T cell migration.     

Implant supported dentures: an estimation of chewing efficiency

doi: 10.1111/j.1741‐2358.2009.00303.x
Implant supported dentures: an estimation of chewing efficiency Background: Treatment of edentulous patients is one of the most demanding tasks the dentist can meet in his everyday practice. Implant based methods help to improve functioning of dentures and life quality of so treated patients. Objectives: The aim of the study was to evaluate the chewing efficiency of patients treated with lower complete implant‐supported overdentures and the simultaneous evaluation of treatment results by patients. Materials and methods: For the investigation were chosen edentulous patients, treated with upper conventional complete dentures and lower complete overdentures supported on two implants. In this group of patients, were conducted investigations of chewing efficiency changes, based on the Optocal test and overdentures functioning evaluation made by patients in the survey. Results: The objective evaluation of the chewing efficiency indicated the decrease of this value in the five years of observations. Lower complete overdentures supported on implants significantly increased the comfort of chewing of edentulous patients. Conclusions: The results of the study let us to assess positively the result of the therapy using titanium implants and lower complete overdentures. The therapy described significantly increases the life comfort of the edentulous patients. Decreasing chewing efficiency indicated by the research result should be compensated with the dentures maintaining or the prostheses exchange after about five years of use.     

Chemically-induced affinity star restriction specificity: a novel TspGWI/sinefungin endonuclease with theoretical 3-bp cleavage frequency

The type IIS/IIC restriction endonuclease TspGWI recognizes the sequence 5'-ACGGA-3', cleaving DNA 11/9 nucleotides downstream. Here we show that sinefungin, a cofactor analog of S-adenosyl methionine, induces a unique type of relaxation in DNA recognition specificity. In the presence of sinefungin, TspGWI recognizes and cleaves at least 12 degenerate variants of the original recognition sequence that vary by single base pair changes from the original 5-bp restriction site with only a single degeneracy per variant appearing to be allowed. In addition, sinefungin was found to have a stimulatory effect on cleavage at these nondegenerate TspGWI recognition sites, irrespective of their number or the DNA topology. Interestingly, no fixed "core" could be identified among the new recognition sequences. Theoretically, TspGWI cleaves DNA every 1024 bp, while sinefungin-induced activity cleaves every 78.8 bp, corresponding to a putative 3-bp long recognition site. Thus, the combination of sinefungin and TspGWI represents a novel frequent cutter, next only to CviJI/CviJI*, that should prove useful in DNA cloning methodologies.