Some properties of a glycoprotein with calcium binding ability found in human biological fluids in macroglobulinaemia IgM

An acidic glycoprotein with calcium-binding properties was isolated from the urine of patients with severe macroglobulinaemia IgM. The molecular weight of this protein determined by Sephadex gel filtration was found to be 62 000 ± 2800 in Tris · HCl buffer and 21 000 ± 1 000 in 6 M guanidine · HCl. The amino acid and carbohydrate composition of the isolated glycoprotein is presented. Electrophoretic migration of this protein was observed to be greatly affected by calcium ions present in the buffer in a concentration of 10^?3 M. At least two sets of binding sites seem to participate in binding calcium. The values 2.2 · 10⁶ M^?1 for the apparent association constant and 4.4 · 10^?4 mol of Ca²⁺ bound per g of protein for high affinity binding sites were estimated, on the basis of data from the equilibrium dialysis. The origin possible biological role of this protein is discussed.     

Failure to induce neonatal tolerance in mice that lack both IL-4 and IL-13 but not in those that lack IL-4 alone.

Current evidence suggests that neonatal tolerance to a foreign Ag is the consequence of IL-4-mediated Th2 immunity rather than the thymic deletion of Ag-specific T cells. Here, we addressed the role of IL-4 in neonatal tolerance by testing whether tolerance to a minor histocompatibility Ag can be induced in newborn mice that lack IL-4 (IL-4(-/-)). We found that IL-4 does not play a dominant role in the induction of neonatal tolerance as newborn female IL-4(-/-) mice could be readily tolerized to the H-Y male Ag. In contrast, mice that lack both IL-4 and IL-13 (IL-4(-/-)/IL-13(-/-)) were resistant to the induction of neonatal tolerance, and their splenocytes produced exaggerated amounts of IFN-gamma on rechallenge with the same Ag encountered during the neonatal period. These findings argue against the view that IL-4 alone is critical for the induction of neonatal tolerance and suggest that the combined actions of both IL-4 and IL-13 are essential for this process.     

Plk1 Phosphorylation of PTEN Causes a Tumor-Promoting Metabolic State

One outcome of activation of the phosphatidylinositol 3-kinase (PI3K) pathway is increased aerobic glycolysis, but the upstream signaling events that regulate the PI3K pathway, and thus the Warburg effect, are elusive. Increasing evidence suggests that Plk1, a cell cycle regulator, is also involved in cellular events in addition to mitosis. To test whether Plk1 contributes to activation of the PI3K pathway, and thus aerobic glycolysis, we examined potential targets of Plk1 and identified PTEN as a Plk1 substrate. We hypothesize that Plk1 phosphorylation of PTEN leads to its inactivation, activation of the PI3K pathway, and the Warburg effect. Our data show that overexpression of Plk1 leads to activation of the PI3K pathway and enhanced aerobic glycolysis. In contrast, inhibition of Plk1 causes markedly reduced glucose metabolism in mice. Mechanistically, we show that Plk1 phosphorylation of PTEN and Nedd4-1, an E3 ubiquitin ligase of PTEN, results in PTEN inactivation. Finally, we show that Plk1 phosphorylation of PTEN promotes tumorigenesis in both its phosphatase-dependent and -independent pathways, revealing potentially new drug targets to arrest tumor cell growth.     

Replication and partitioning of the broad-host-range plasmid RK2

The broad-host-range plasmid RK2 has been a model for studying DNA metabolism in bacteria for many years. It is used as a vector allowing genetic manipulations in numerous bacterial species. The RK2 genome encodes several genes providing the plasmid with diverse functions allowing for its stable maintenance in a variety of bacterial hosts. This review will focus on two processes indispensable for plasmid DNA maintenance. We will summarize recent understanding of the molecular mechanisms contributing to the RK2 DNA replication and partitioning.     

IncP-9 replication initiator protein binds to multiple DNA sequences in oriV and recruits host DnaA protein

The minimal replicon from IncP-9 plasmid pM3, consisting of oriV and rep, is able to replicate in Pseudomonas putida but not in Escherichia coli, unless production of Rep protein is increased. The Rep protein, at 20kDa, is the smallest replication protein so far identified for a theta replicating plasmid. Rep was purified and shown to bind in three blocks across the oriV region that do not correlate with a single unique binding sequence. The block closest to rep is not necessary for oriV function. Rep forms at least two types of complex--one rendering the DNA entirely resistant to cleavage, the other occupying one side of the helix. No short segment of oriV showed the same affinity for Rep as the whole of oriV. The oriV region did not bind purified DnaA from E. coli, P. putida or P. aeruginosa but when Rep was present also, super-shifts were found with DnaA in a sequence-specific manner. Scrambling of the primary candidate DnaA box did not inactivate oriV but did increase the level of Rep required to activate oriV. The general pattern of Rep-DNA recognition sequences in oriV indicates that the IncP-9 system falls outside of the paradigms of model plasmids that have been well-studied to date.     

Defining a novel domain that provides an essential contribution to site-specific interaction of Rep protein with DNA

An essential feature of replication initiation proteins is their ability to bind to DNA. In this work, we describe a new domain that contributes to a replication initiator sequence-specific interaction with DNA. Applying biochemical assays and structure prediction methods coupled with DNA–protein crosslinking, mass spectrometry, and construction and analysis of mutant proteins, we identified that the replication initiator of the broad host range plasmid RK2, in addition to two winged helix domains, contains a third DNA-binding domain. The phylogenetic analysis revealed that the composition of this unique domain is typical within the described TrfA-like protein family. Both in vitro and in vivo experiments involving the constructed TrfA mutant proteins showed that the newly identified domain is essential for the formation of the protein complex with DNA, contributes to the avidity for interaction with DNA, and the replication activity of the initiator. The analysis of mutant proteins, each containing a single substitution, showed that each of the three domains composing TrfA is essential for the formation of the protein complex with DNA. Furthermore, the new domain, along with the winged helix domains, contributes to the sequence specificity of replication initiator interaction within the plasmid replication origin.     

Two-intermediate model to characterize the structure of fast-folding proteins

This paper introduces a new model that enables researchers to conduct protein folding simulations. A two-step in silico process is used in the course of structural analysis of a set of fast-folding proteins. The model assumes an early stage (ES) that depends solely on the backbone conformation, as described by its geometrical properties—specifically, by the V-angle between two sequential peptide bond planes (which determines the radius of curvature, also called R-radius, according to a second-degree polynomial form). The agreement between the structure under consideration and the assumed model is measured in terms of the magnitude of dispersion of both parameters with respect to idealized values. The second step, called late-stage folding (LS), is based on the “fuzzy oil drop” model, which involves an external hydrophobic force field described by a three-dimensional Gauss function. The degree of conformance between the structure under consideration and its idealized model is expressed quantitatively by means of the Kullback-Leibler entropy, which is a measure of disparity between the observed and expected hydrophobicity distributions. A set of proteins, representative of the fast-folding group - specifically, cold shock proteins - is shown to agree with the proposed model.     

Stable transformation of Mesembryanthemum crystallinum (L.) with Agrobacterium rhizogenes harboring the green fluorescent protein targeted to the endoplasmic reticulum

Stable transformation of Mesembryanthemum crystallinum L. (common ice plant) with a green fluorescent protein (GFP) construct targeted to the endoplasmic reticulum was obtained. Seven and fourteen days after germination seedlings were infected with Agrobacterium rhizogenes strain ARqua1 either by direct coating of the cut radicles with bacteria growing on solid medium or by immersion of the cut surface in bacterial suspension at different optical densities. Both methods of infection resulted in production of GFP-positive roots with a frequency ranging from 6 to 20% according to the age of the explants and the application procedure. The green fluorescing roots displayed the typical hairy root phenotype and were easily maintained in liquid medium without growth regulators for over 2 years. Stable expression of the transgene in the roots was confirmed by polymerase chain reaction (PCR), immunoblotting and the capacity of roots to grow and produce callus on kanamycin-enriched medium. Nineteen endogenous cytokinins were determined in transgenic and non-transformed roots. The results revealed significantly lower levels of the free bases of isopentenyladenine, dihydrozeatin, cis- and trans-zeatin, as well as a conspicuous decline in concentrations of the corresponding nucleosides and most nucleotides in transgenic roots compared to the wild type. Comparison of the cytokinin profiles in transgenic and non-transformed roots suggested that transformation by A. rhizogenes disturbed cytokinin metabolism during the early steps of biosynthesis. Calli obtained from transformed roots were GFP-positive and remained non-regenerative or displayed high rhizogenic potential depending on the auxin/cytokinin ratio in the medium. Calli and callus-derived roots showed a strong GFP signal for over 2 years.     

Exenatide promotes cognitive enhancement and positive brain metabolic changes in PS1-KI mice but has no effects in 3xTg-AD animals

Recent studies have shown that type 2 diabetes mellitus (T2DM) is a risk factor for cognitive dysfunction or dementia. Insulin resistance is often associated with T2DM and can induce defective insulin signaling in the central nervous system as well as increase the risk of cognitive impairment in the elderly. Glucagone like peptide-1 (GLP-1) is an incretin hormone and, like GLP-1 analogs, stimulates insulin secretion and has been employed in the treatment of T2DM. GLP-1 and GLP-1 analogs also enhance synaptic plasticity and counteract cognitive deficits in mouse models of neuronal dysfunction and/or degeneration. In this study, we investigated the potential neuroprotective effects of long-term treatment with exenatide, a GLP-1 analog, in two animal models of neuronal dysfunction: the PS1-KI and 3xTg-AD mice. We found that exenatide promoted beneficial effects on short- and long-term memory performances in PS1-KI but not in 3xTg-AD animals. In PS1-KI mice, the drug increased brain lactate dehydrogenase activity leading to a net increase in lactate levels, while no effects were observed on mitochondrial respiration. On the contrary, exenatide had no effects on brain metabolism of 3xTg-AD mice. In summary, our data indicate that exenatide improves cognition in PS1-KI mice, an effect likely driven by increasing the brain anaerobic glycolysis rate.