Alkaloid diversification in the genus Palicourea (Rubiaceae: Palicoureeae) viewed from a (retro-)biogenetic perspective

Phytochemistry Reviews - The species-rich genus Palicourea (Rubiaceae: Palicoureeae) is source of an intriguing diversity of alkaloids derived from tryptamine and its precursor tryptophan. So far...     

A revised classification of the sister tribes Palicoureeae and Psychotrieae (Rubiaceae) indicates genus-specific alkaloid accumulation

Phytochemistry Reviews - Tribes Palicoureeae and Psychotrieae (Rubiaceae, Gentianales) are complex and speciose sister groups with a pantropical distribution. Since the initial studies on...     

Das essenzielle Spurenelement Zink. Ein Metall in Biologie und Medizin

The essential trace element zinc The human body contains 2–3 grams of the essential trace element zinc, and uptake as well as excretion underlies a tight control. If this balance is disturbed, a number of biological processes are affected: among other tasks, zinc is important for the development and function of the central nervous system, the immune defense, and the production and function of insulin. This is based on over 300 different zinc‐containing enzymes, several other zinc proteins, and a role of zinc in intracellular signal transduction.     

The LysE superfamily: topology of the lysine exporter LysE of Corynebacterium glutamicum, a paradyme for a novel superfamily of transmembrane solute translocators

In Corynebacterium glutamicum the LysE carrier protein exhibits the unique function of exporting L-lysine. We here analyze the membrane topology of LysE, a protein of 236 amino acyl residues, using PhoA- and LacZ-fusions. The amino-terminal end of LysE is located in the cytoplasm whereas the carboxy-terminal end is found in the periplasm. Although 6 hydrophobic domains were identified based on hydropathy analyses, only five transmembrane spanning helices appear to be present. The additional hydrophobic segment may dip into the membrane or be surface localized. We show that LysE is a member of a family of proteins found, for example, in Escherichia coil, Bacillus subtilis, Mycobacterium tuberculosis and Helicobacter pylori. This family, which we have designated the LysE family, is distantly related to two additional protein families which we have designated the YahN and CadD families. These three families, the members of which exhibit similar sizes, hydropathy profiles, and sequence motifs comprise the LysE superfamily. Functionally characterized members of the LysE superfamily export L-lysine, cadmium and possibly quarternary amines. We suggest that LysE superfamily members will prove to catalyze export of a variety of biologically important solutes.     

Hypoxia-induced erythropoietin expression in human neuroblastoma requires a methylation free HIF-1 binding site

The glycoprotein hormone Erythropoietin (EPO) stimulates red cell production and maturation. EPO is produced by the kidneys and the fetal liver in response to hypoxia (HOX). Recently, EPO expression has also been observed in the central nervous system where it may be neuroprotective. It remained unclear, however, whether EPO is expressed in the peripheral nervous system and, if so, whether a neuronal phenotype is required for its regulation. Herein, we report that EPO expression was induced by HOX and a HOX mimetic in two cell lines derived from neuroblastoma (NB), a tumor of the peripheral nervous system. Both cell lines with inducible EPO expression, SH-SY5Y and Kelly cells, expressed typical neuronal markers like neuropeptide Y (NPY), growth-associated protein-43 (GAP-43), and neuron-specific enolase (ENO). NB cells with a more epithelial phenotype like SH-SHEP and LAN-5 did not show HOX inducible EPO gene regulation. Still, oxygen sensing and up-regulation of hypoxia-inducible factor-1 (HIF-1) were intact in all cell lines. We found that CpG methylation of the HIF binding site (HBS) in the EPO gene 3' enhancer was only present in the SH-SHEP and LAN-5 cells but not in SH-SY5Y and Kelly cells with regulated EPO expression. The addition of recombinant EPO to all NB cells, both under normoxic and hypoxic conditions, had no effect on cell proliferation. We conclude that the ability to respond to HOX with an increase in EPO expression in human NB may depend on CpG methylation and the differentiation status of these embryonic tumor cells but does not affect the proliferative characteristics of the cells.     

Lignification and structural biomass production in tobacco with suppressed caffeic/5-hydroxy ferulic acid-O-methyl transferase activity under ambient and elevated CO concentrations

To investigate the relationship between growth, biomass partitioning and lignification we used tobacco (Nicotiana tabacum) in which O-methyl transferase (OMT) activity, an enzyme involved in the pathway of sinapyl alcohol formation for lignin synthesis, was suppressed by antisense transformation. To modulate growth, controls and transformed tobacco plants were grown under ambient (approximately 380 p.p.m) or elevated CO(2) (700 p.p.m), respectively. Lignin concentrations and composition were determined with spectrophotometric methods (thioglycolate and acetyl bromide) and Fourier transform infrared (FTIR) spectroscopy, respectively. A comparison of the thioglycolate and acetylbromide method suggested that the thioglycolate method was sensitive to changes in the syringyl/guaiacyl (S/G)-ratio in lignin and therefore not suitable for quantification in tissues with altered lignin composition. Growth under elevated CO(2) increased leaf and stem biomass of both genotypes by 40 and 20%, respectively, compared with ambient CO(2) and had no effect on root biomass. OMT suppression did not affect lignin concentrations in the leaves but caused a shift in biomass partitioning from the structural to the non-structural fraction. Elevated CO(2) caused a shift towards production of structural compounds resulting in decreased foliar lignin concentrations and indicating that the lignin/structural mass ratio is flexible in leaves. By contrast, the lignin concentrations of stems were unaffected by elevated CO(2) or OMT suppression and increased about three-fold from the apex to the base. Antisense-OMT plants produced more stem biomass than controls but showed no changes of the relative partitioning of biomass to the different pools. This indicates that the metabolic control of carbon fluxes to the production of structural versus non-structural fractions is tighter in stems than in leaves. FTIR spectroscopy indicated a relative increase in guaiacyl- as compared with syringyl-units in antisense-OMT tobacco, which was more pronounced under elevated as compared with ambient CO(2). Since there was no evidence for decreased lignin concentrations in the antisense-OMT plants but increased biomass formation we suggest that less methylated lignins are 'cheaper' in biosynthetic carbon and energy demand and, thus, may enable plants to allocate increased resources to growth.     

The proliferation associated nuclear element (PANE1) is conserved between mammals and fish and preferentially expressed in activated lymphoid cells

The proliferation associated nuclear element (PANE1) had been identified in a screen for genes activated in mouse mammary epithelium transformed by stabilized beta-catenin. We have now cloned the human and zebrafish orthologs, analyzed their expression and expressed them ectopically in tissue culture cell lines. PANE1 consists of 180 amino acids and displays 38% conservation between man and zebrafish. Expression of the human PANE1 gene was detected preferentially in immune cells including leukemias and lymphomas, tumor tissues and tumor derived cell lines. In B- and T-cells PANE1 RNA was only detected after the respective cell types were activated either in vivo or in vitro.     

Activated protein C inhibits the release of macrophage inflammatory protein-1-alpha from THP-1 cells and from human monocytes

Several lines of evidence have implicated activated protein C (APC) to be an endogenous inhibitor of the inflammatory septic cascade. APC may exhibit direct anti-inflammatory properties, independent of its antithrombotic effects. Chemokines influence the interaction of monocytes at the endothelium during infection and sepsis and are involved in the molecular events leading to an adverse and lethal outcome of sepsis. Defining regulatory mechanisms on the monocytic release profile of the proinflammatory C-C chemokines macrophage inflammatory protein-1-alpha (MIP-1-alpha) and monocyte chemoattractant protein-1 (MCP-1) might have therapeutic implications for the treatment of sepsis. We established a monocytic cell model of inflammation by the addition of lipopolysaccharide (LPS) and examined the effect of human APC on LPS-stimulated chemokine release from the monocytic cell line THP-1. We found that human APC in supra-physiological concentrations of 2.5-10 microg/ml inhibited the LPS-induced release of the chemokines MIP-1-alpha and MCP-1, as measured by enzyme-linked immunosorbent assays (ELISA) at 6 up to 24 h. In addition to experiments on THP-1 cells, recombinant human APC in concentrations of 50 ng/ml was found to have an inhibiting effect on the release of MIP-1-alpha from freshly isolated mononuclear cells of septic patients. The ability of APC to decrease the release of the C-C chemokine MIP-1-alpha from the monocytic cell line THP-1 and from human monocytes may identify a novel immunomodulatory pathway by which APC exerts its anti-inflammatory action and may contribute to control the inflammatory response in sepsis.