Genetically modified plants in phytoremediation of heavy metal and metalloid soil and sediment pollution

Phytoremediation to clean up metal- and metalloid-contaminated soil or sediments has gained increasing attention as environmental friendly and cost effective. Achievements of the last decade suggest that genetic engineering of plants can be instrumental in improving phytoremediation. Transgenic approaches successfully employed to promote phytoextraction of metals (mainly Cd, Pb, Cu) and metalloids (As, Se) from soil by their accumulation in the aboveground biomass involved mainly implementation of metal transporters, improved production of enzymes of sulphur metabolism and production of metal-detoxifying chelators — metallothioneins and phytochelatins. Plants producing bacterial mercuric reductase and organomercurial lyase can covert the toxic ion or organomercury to metallic Hg volatized from the leaf surface. Phytovolatization of selenium compounds was promoted in plants overexpressing genes encoding enzymes involved in production of gas methylselenide species. This paper provides a broad overview of the evidence supporting suitability and prospects of transgenic research in phytoremediation of heavy metals and metalloids.     

L1 endocytosis is controlled by a phosphorylation-dephosphorylation cycle stimulated by outside-in signaling by L1

Dynamic regulation of the cell surface expression of adhesion molecules is an important mechanism for controlling neuronal growth cone motility and guidance. Clathrin-mediated vesicular internalization of L1 via the tyrosine-based endocytosis motif YRSL regulates adhesion and signaling by this Ig superfamily molecule. Here, we present evidence that tyrosine-1176 (Y1176) of the YRSL motif is phosphorylated in vivo. The nonreceptor tyrosine kinase (p60src) is implicated in L1-mediated neurite outgrowth, and we find that p60src phosphorylates Y1176 in vitro. Phosphorylation of Y1176 prevents L1 binding to AP-2, an adaptor required for clathrin-mediated internalization of L1. mAb 74-5H7 recognizes the sequence immediately NH2-terminal to the tyrosine-based motif and binds L1 only when Y1176 is dephosphorylated. 74-5H7 identifies a subset of L1 present at points of cell-cell contact and in vesicle-like structures that colocalize with an endocytosis marker. L1-L1 binding or L1 cross-linking induces a rapid increase in 74-5H7 immunoreactivity. Our data suggest a model in which homophilic binding or L1 cross-linking triggers transient dephosphorylation of the YRSL motif that makes L1 available for endocytosis. Thus, the regulation of L1 endocytosis through dephosphorylation of Y1176 is a critical regulatory point of L1-mediated adhesion and signaling.     

N-[2-(Indan-1-yl)-3-mercapto-propionyl] amino acids as highly potent inhibitors of the three vasopeptidases (NEP,ACE, ECE): In vitro and In vivo activities

We have previously reported the design of a lead compound 1a for the joint inhibition of neprilysin (NEP, EC 3.4.24.11), angiotensin converting enzyme (ACE, EC 3.4.15.1) and endothelin converting enzyme (ECE-1, EC 3.4.24.71), three metallopeptidases which are implicated in the regulation of fluid homeostasis and vascular tone. We report here the synthesis and biological activities of analogues derived from this lead with inhibitory potencies in the nanomolar range for the three enzymes. Compounds 8b and 15c are the most potent triple inhibitors described to date.     

Behavioral and metabolic characterization of heterozygous and homozygous POLG mutator mice

The mitochondrial DNA (mtDNA) polymerase γ (POLG) mutator mice provide the first experimental evidence that high levels of somatic mtDNA mutations can be functionally significant. Here we report that older homozygous, but not heterozygous, POLG mice show significant reductions in striatal dopaminergic terminals as well as deficits in motor function. However, resting oxygen consumption, heat production, mtDNA content and mitochondrial electron transport chain activities are significantly decreased at older ages in both homozygous and heterozygous mice. These results indicate that high levels of somatic mtDNA mutations can contribute to dopaminergic dysfunction and to behavioral and metabolic deficits.     

DNA methylation pattern in pig in vivo produced embryos

DNA methylation/demethylation pattern, determined by 5-methylcytosine (5-MeC) immunostaining, was evaluated in porcine “in vivo” produced embryos from zygote up to the blastocyst stage. In one-cell stage embryos, only the maternal pronucleus showed a positive labeling whilst the paternal pronucleus showed almost no labeling. The intensity of labeling is high until the late morula stage. Blastocysts containing less than 100 cells showed the same intensity of labeling in both the inner cell mass (ICM) nuclei and the trophectodermal (TE) cell nuclei. Interestingly, with further cell multiplication, cells of the ICM became more intensively labeled when compared to TE cells. This distinct methylation pattern is even more profound in blastocysts containing about 200–300 cells and is not caused by the difference in the cell volume of ICM and TE cells.An erratum to this article can be found at     

PAT1a modulates intracellular transport and processing of amyloid precursor protein (APP), APLP1, and APLP2

Understanding the intracellular transport of the beta-amyloid precursor protein (APP) is a major key to elucidate the regulation of APP processing and thus beta-amyloid peptide generation in Alzheimer disease pathogenesis. APP and its two paralogues, APLP1 and APLP2 (APLPs), are processed in a very similar manner by the same protease activities. A putative candidate involved in APP transport is protein interacting with APP tail 1 (PAT1), which was reported to interact with the APP intracellular domain. We show that PAT1a, which is 99.0% identical to PAT1, binds to APP, APLP1, and APLP2 in vivo and describe their co-localization in trans-Golgi network vesicles or endosomes in primary neurons. We further demonstrate a direct interaction of PAT1a with the basolateral sorting signal of APP/APLPs. Moreover, we provide evidence for a direct role of PAT1a in APP/APLP transport as overexpression or RNA interference-mediated knockdown of PAT1a modulates APP/APLPs levels at the cell surface. Finally, we show that PAT1a promotes APP/APLPs processing, resulting in increased secretion of beta-amyloid peptide. Taken together, our data establish PAT1a as a functional link between APP/APLPs transport and their processing.     

The nop gene from Phanerochaete chrysosporium encodes a peroxidase with novel structural features

Inspection of the genome of the ligninolytic basidiomycete Phanerochaete chrysosporium revealed an unusual peroxidase_like sequence. The corresponding full length cDNA was sequenced and an archetypal secretion signal predicted. The deduced mature protein (NoP, novel peroxidase) contains 295 aa residues and is therefore considerably shorter than other Class II (fungal) peroxidases, such as lignin peroxidases and manganese peroxidases. Comparative modeling of NoP was conducted using the crystal structures of Coprinus cinereus and Arthromyces ramosus peroxidases as templates. The model was validated by molecular dynamics and showed several novel structural features. In particular, NoP has only three disulfide bridges and tryptophan replaces the distal phenylalanine within the heme pocket.     

mPER1-mediated nuclear export of mCRY1/2 is an important element in establishing circadian rhythm

Receptor-mediated nucleocytoplasmic transport of clock proteins is an important, conserved element of the core mechanism for circadian rhythmicity. A systematic analysis of the nuclear export characteristics for the different murine period (mPER) and cryptochrome (mCRY) proteins using Xenopus oocytes as an experimental system demonstrates that all three mPER proteins, but neither mCRY1 nor mCRY2, are exported if injected individually. However, nuclear injection of heterodimeric complexes that contain combinations of mPER and mCRY proteins shows that mPER1 serves as an export adaptor for mCRY1 and mCRY2. Functional analysis of dominant-negative mPER1 variants designed either to sequester mPER3 to the cytoplasm or to inhibit nuclear export of mCRY1/2 in synchronized, stably transfected fibroblasts suggests that mPER1-mediated export of mCRY1/2 defines an important new element of the core clock machinery in vertebrates.