Functional Effects of Adiponectin on Endothelial Progenitor Cells

Adiponectin is an adipokine whose plasma levels are inversely correlated to metabolic syndrome components. Adiponectin protects against atherosclerosis and decreases risks in myocardial infarction. Endothelial progenitor cells (EPCs) are a heterogeneous population of circulating cells involved in vascular repair and neovascularization. EPCs number is reduced in patients with cardiovascular disease. We hypothesize that the positive effects of adiponectin against atherosclerosis are explained in part by its interactions with EPCs. Cells were obtained from healthy volunteers' blood by mononuclear cell isolation and plating on collagen‐coated dishes. Three sub‐populations of EPCs were identified and characterized using flow cytometry. EPCs' expression of adiponectin receptors, AdipoR1, and AdipoR2 was evaluated by quantitative PCR. The effects of recombinant adiponectin on EPCs' susceptibility to apoptosis were assessed. Finally, expression of neutrophil elastase by EPCs and activity of this enzyme on adiponectin processing were assessed. Quantitative PCR analysis of EPCs mRNAs showed that AdipoR1 mRNA is expressed at higher levels than AdipoR2. Expression of AdipoR1 protein was confirmed by western blot. Adiponectin significantly increased survival of two sub‐populations of EPCs in conditions of serum deprivation. Such effect could not be demonstrated in the third EPCs sub‐population. We also demonstrated that EPCs, particularly one sub‐population, express neutrophil elastase. Neutrophil elastase activity was confirmed in EPCs' conditioned media. Adiponectin protects some EPCs sub‐populations against apoptosis and therefore could modulate EPCs ability to induce repair of vascular damage. Neutrophil elastase activity of EPCs could locally modulate adiponectin activity by its involvement in the generation of the globular form of adiponectin.     

Mechanisms of HIV-1 evasion to the antiviral activity of chemokine CXCL12 indicate potential links with pathogenesis

HIV-1 infects CD4 T lymphocytes (CD4TL) through binding the chemokine receptors CCR5 or CXCR4. CXCR4-using viruses are considered more pathogenic, linked to accelerated depletion of CD4TL and progression to AIDS. However, counterexamples to this paradigm are common, suggesting heterogeneity in the virulence of CXCR4-using viruses. Here, we investigated the role of the CXCR4 chemokine CXCL12 as a driving force behind virus virulence. In vitro, CXCL12 prevents HIV-1 from binding CXCR4 and entering CD4TL, but its role in HIV-1 transmission and propagation remains speculative. Through analysis of thirty envelope glycoproteins (Envs) from patients at different stages of infection, mostly treatment-naïve, we first interrogated whether sensitivity of viruses to inhibition by CXCL12 varies over time in infection. Results show that Envs resistant (RES) to CXCL12 are frequent in patients experiencing low CD4TL levels, most often late in infection, only rarely at the time of primary infection. Sensitivity assays to soluble CD4 or broadly neutralizing antibodies further showed that RES Envs adopt a more closed conformation with distinct antigenicity, compared to CXCL12-sensitive (SENS) Envs. At the level of the host cell, our results suggest that resistance is not due to improved fusion or binding to CD4, but owes to viruses using particular CXCR4 molecules weakly accessible to CXCL12. We finally asked whether the low CD4TL levels in patients are related to increased pathogenicity of RES viruses. Resistance actually provides viruses with an enhanced capacity to enter naive CD4TL when surrounded by CXCL12, which mirrors their situation in lymphoid organs, and to deplete bystander activated effector memory cells. Therefore, RES viruses seem more likely to deregulate CD4TL homeostasis. This work improves our understanding of the pathophysiology and the transmission of HIV-1 and suggests that RES viruses’ receptors could represent new therapeutic targets to help prevent CD4TL depletion in HIV+ patients on cART.     

Glycosylation of human leukocyte locus A molecules is dependent on the cell type

Peripheral blood monocytes and B cells were isolated from a normal donor, and a portion of the B cells was transformed by the Epstein-Barr virus (EBV). Human leukocyte locus A (HLA) class-I and class-II molecules were immunoprecipitated by specific monoclonal antibodies after cell labeling with [3H]mannose. Glycopeptides of HLA molecules were obtained by pronase digestion and were analysed by lectin-affinity chromatography. Complex structures were hydrazinolysed, and their sialic acid content was analysed by ion-exchange chromatography, whereas the high-mannose structures were separated by HPLC. In normal cells, class-I antigens bear principally fucosylated biantennary structures while HLA-DR class-II antigens bear bi-, tri- and tetra-antennary structures and high-mannose structures. HLA antigens are more sialylated on normal B cells than on normal monocytes. An EBV cell line had a very different pattern of HLA-antigen glycosylation when compared with the original B cells. In the transformed cells, the fractions containing biantennary structures are largely decreased. In contrast, an increase of the tri- and tetra-antennary structure fractions is noticed, particularly in class-II molecules, while both triantennary and high-mannose structures are increased in class-I molecules. Moreover, when compared to normal B cells, the complex structures of class-I antigens in the EBV-transformed B-cell line are undersialylated while they are oversialylated in the case of the class-II molecules.     

Molecular Evolution of the Telomere-Associated Mal Loci of Saccharomyces

The MAL gene family of Saccharomyces consists of five multigene complexes (MAL1, MAL2, MAL3, MAL4, and MAL6) each of which encodes maltose permease (GENE 1), maltase (GENE 2) and the trans-acting MAL-activator (GENE 3). Four of these loci have been mapped and each is located at or near the telomere of a different chromosome. We compare the physical structure of the MAL loci and their flanking sequences. The MAL loci were shown to be both structurally and functionally homologous throughout an approximately 9.0-kb region. The orientation of the MAL loci was determined to be: CENTROMERE . . . GENE 3-GENE 1-GENE 2 . . . TELOMERE. Telomere-adjacent sequences were found flanking GENE 2 of the MAL1, MAL3 and MAL6 loci. No common repeated elements were found on the centromere-proximal side of all the MAL1, loci. These results suggest that, during the evolution of this polygenic family, the MAL loci translocated to different chromosomes via a mechanism that involved the rearrangement(s) of chromosome termini.     

Porcine D-amino acid oxidase: production of the biologically active enzyme in Escherichia coli

DNA molecules coding either for mature porcine D-amino acid oxidase or for truncated forms of the enzyme have been obtained by stepwise addition of synthetic oligonucleotides to a partial cDNA. Under the control of the lambda PL thermoregulatable promoter, these DNAs were respectively expressed in Escherichia coli as 36, 28 and 25 kilodalton polypeptides, specifically recognised by antibodies raised against the natural enzyme. None of the truncated proteins were biologically active whereas the mature recombinant species was able to hydrolyze D-alanine in vitro as efficiently as the natural product.     

High-frequency disruption of the N-myc gene in embryonic stem and pre-B cell lines by homologous recombination.

Identification of gene function has often relied on isolation of mutant cells in which expression of the gene was inactivated. Gene targeting by homologous recombination in tissue culture now may provide a technology to rapidly and directly produce such mutant mammalian cells. We demonstrate that selection of embryonic stem and pre-B cell lines for expression of a promoterless construct containing murine N-myc genomic sequences fused to a gene encoding neomycin resistance allows highly efficient recovery of variants in which the endogenous N-myc gene is disrupted. The high frequency of N-myc gene disruption by this method should permit targeted disruption of both allelic N-myc copies in various cell lines to study N-myc function.     

Developmental expression and cellular localization of glucose transporter molecules during mouse preimplantation development.

Two general mechanisms mediate glucose transport, one is a sodium-coupled glucose transporter found in the apical border of intestinal and kidney epithelia, while the other is a sodium-independent transport system. Of the latter, several facilitated transporters have been identified, including GLUT1 (erythrocyte/brain), GLUT2 (liver) and GLUT4 (adipose/muscle) isoforms. In this study, we used Western-blot analysis and high resolution immunoelectron microscopy (IEM) to investigate the stage-related expression and cellular localization of GLUT1, 2 and 4. The Western blot results demonstrate that GLUT1 is detectable in the oocyte and throughout preimplantation development. GLUT2 isoforms were not detectable until the blastocyst stage, while the GLUT4 isoform was undetectable in the oocyte through blastocyst stages. The present findings confirm previous studies at the molecular level which demonstrated that mRNAs encoding the same GLUT isoforms are detectable at corresponding developmental stages. GLUT1 and GLUT2 display different cellular distributions at the blastocyst stage as shown by IEM studies. GLUT1 has a widespread distribution in both trophectoderm and inner cell mass cells, while GLUT2 is located on trophectoderm membranes facing the blastocyst cavity. This observation suggests a different functional significance for these isoforms during mouse preimplantation development.     

The Naturally Occurring Alleles of Mal1 in Saccharomyces Species Evolved by Various Mutagenic Processes Including Chromosomal Rearrangement

In order for a yeast strain to ferment maltose it must contain any one of the five dominant MAL loci. Each dominant MAL locus thus far analyzed contains three genes: GENE 1, encoding maltose permease, GENE 2 encoding maltase and GENE 3 encoding a positive trans-acting regulatory protein. In addition to these dominant MAL loci, several naturally occurring, partially functional alleles of MAL1 and MAL3 have been identified. Here, we present genetic and molecular analysis of the three partially functional alleles of MAL1: the MAL1p allele which can express only the MAL activator; the MAL1 g allele which can express both a maltose permease and maltase; and the mal1(0) allele which can express only maltase. Based on our results, we propose that the MAL1p, MAL1g and mal1(0) alleles evolved from the dominant MAL1 locus by a series of rearrangements and/or deletions of this yeast telomere-associated locus as well as by other mutagenic processes of gene inactivation. One surprising finding is that the MAL1g-encoded maltose permease exhibits little sequence homology to the MAL1-encoded maltose permease though they appear to be functionally homologous.