Formyl peptide receptors: a promiscuous subfamily of G protein-coupled receptors controlling immune responses

The formyl peptide receptor (FPR) family is involved in host defence against pathogens, but also in sensing internal molecules that may constitute signals of cellular dysfunction. It includes three subtypes in human and other primates. FPR responds to formyl peptides derived from bacterial and mitochondrial proteins. FPRL1 displays a large array of exogenous and endogenous ligands, including the chemokine variant sCKβ8-1, the neuroprotective peptide humanin, and lipoxin A4. Two high affinity agonists (F2L and humanin) were recently described for FPRL2. In mouse, eight FPR-related receptors have been described. Fpr1 is the ortholog of human FPR, while fpr2 appears to share many ligands with human FPRL1. Altogether, the physiological role of the FPR family is still incompletely understood, due in part to the large variety of ligands, the redundancy with other chemoattractant agents, and the lack of clear orthologs between human and mouse receptors. Newly developed tools will allow to study further this family of receptors.     

Comparative proteome profiling and functional analysis of chronic myelogenous leukemia cell lines

The aim of the present study was the molecular profiling of different Ph+ chronic myelogenous leukemia (CML) cell lines (LAMA84, K562, and KCL22) by a proteomic approach. By employing two-dimensional gel electrophoresis combined with mass spectrometry analysis, we have identified 191 protein spots corresponding to 142 different proteins. Among these, 63% were cancer-related proteins and 74% were described for the first time in leukemia cells. Multivariate analysis highlighted significant differences in the global proteomic profile of the three CML cell lines. In particular, the detailed analysis of 35 differentially expressed proteins revealed that LAMA84 cells preferentially expressed proteins associated with an invasive behavior, while K562 and KCL22 cells preferentially expressed proteins involved in drug resistance. These data demonstrate that these CML cell lines, although representing the same pathological phenotype, show characteristics in their protein expression profile that suggest different phenotypic leukemia subclasses. These data contribute a new potential characterization of the CML phenotype and may help to understand interpatient variability in the progression of disease and in the efficacy of a treatment.     

The checkpoint Saccharomyces cerevisiae Rad9 protein contains a tandem tudor domain that recognizes DNA

DNA damage checkpoints are signal transduction pathways that are activated after genotoxic insults to protect genomic integrity. At the site of DNA damage, ‘mediator’ proteins are in charge of recruiting ‘signal transducers’ to molecules ‘sensing’ the damage. Budding yeast Rad9, fission yeast Crb2 and metazoan 53BP1 are presented as mediators involved in the activation of checkpoint kinases. Here we show that, despite low sequence conservation, Rad9 exhibits a tandem tudor domain structurally close to those found in human/mouse 53BP1 and fission yeast Crb2. Moreover, this region is important for the resistance of Saccharomyces cerevisiae to different genotoxic stresses. It does not mediate direct binding to a histone H3 peptide dimethylated on K79, nor to a histone H4 peptide dimethylated on lysine 20, as was demonstrated for 53BP1. However, the tandem tudor region of Rad9 directly interacts with single-stranded DNA and double-stranded DNAs of various lengths and sequences through a positively charged region absent from 53BP1 and Crb2 but present in several yeast Rad9 homologs. Our results argue that the tandem tudor domains of Rad9, Crb2 and 53BP1 mediate chromatin binding next to double-strand breaks. However, their modes of chromatin recognition are different, suggesting that the corresponding interactions are differently regulated.     

Reduced secretion and expression of gelatinase profile in Toxoplasma gondii-infected human monocytic cells

The apicomplexan Toxoplasma gondii, an obligate intracellular parasite, can infect humans and a wide range of vertebrates. Following oral infection, the parasite invades tissues by crossing non-permissive biological barriers such as the placenta or the blood-brain barrier. But the molecular mechanisms underlying migration of T. gondii remain poorly characterized. The crossing of various basal membranes and infiltration into the extracellular matrix by T. gondii could involve matrix metalloproteinases (MMPs). We demonstrated a decrease in proMMP-2 and proMMP-9 secretion by THP-1 cells at 24 and 48h post invasion with regulation at the mRNA level throughout infection. This down regulation was associated with a decrease in TIMP-2 secretion and an inhibition of its expression. Moreover, results showed an activation of MT1-MMP; its expression was regulated after 6, 24, and 48h.     

NEDD1-dependent recruitment of the gamma-tubulin ring complex to the centrosome is necessary for centriole duplication and spindle assembly

The centrosome is the major microtubule organizing structure in somatic cells. Centrosomal microtubule nucleation depends on the protein gamma-tubulin. In mammals, gamma-tubulin associates with additional proteins into a large complex, the gamma-tubulin ring complex (gammaTuRC). We characterize NEDD1, a centrosomal protein that associates with gammaTuRCs. We show that the majority of gammaTuRCs assemble even after NEDD1 depletion but require NEDD1 for centrosomal targeting. In contrast, NEDD1 can target to the centrosome in the absence of gamma-tubulin. NEDD1-depleted cells show defects in centrosomal microtubule nucleation and form aberrant mitotic spindles with poorly separated poles. Similar spindle defects are obtained by overexpression of a fusion protein of GFP tagged to the carboxy-terminal half of NEDD1, which mediates binding to gammaTuRCs. Further, we show that depletion of NEDD1 inhibits centriole duplication, as does depletion of gamma-tubulin. Our data suggest that centriole duplication requires NEDD1-dependent recruitment of gamma-tubulin to the centrosome.     

Infection of dendritic cells (DCs), not DC-SIGN-mediated internalization of human immunodeficiency virus, is required for long-term transfer of virus to T cells

The C-type lectin DC-SIGN expressed on immature dendritic cells (DCs) captures human immunodeficiency virus (HIV) particles and enhances the infection of CD4+ T cells. This process, known as trans-enhancement of T-cell infection, has been related to HIV endocytosis. It has been proposed that DC-SIGN targets HIV to a nondegradative compartment within DCs and DC-SIGN-expressing cells, allowing incoming virus to persist for several days before infecting target cells. In this study, we provide several lines of evidence suggesting that intracellular storage of intact virions does not contribute to HIV transmission. We show that endocytosis-defective DC-SIGN molecules enhance T-cell infection as efficiently as their wild-type counterparts, indicating that DC-SIGN-mediated HIV internalization is dispensable for trans-enhancement. Furthermore, using immature DCs that are genetically resistant to infection, we demonstrate that several days after viral uptake, HIV transfer from DCs to T cells requires viral fusion and occurs exclusively through DC infection and transmission of newly synthesized viral particles. Importantly, our results suggest that DC-SIGN participates in this process by cooperating with the HIV entry receptors to facilitate cis-infection of immature DCs and subsequent viral transfer to T cells. We suggest that such a mechanism, rather than intracellular storage of incoming virus, accounts for the long-term transfer of HIV to CD4+ T cells and may contribute to the spread of infection by DCs.     

Aggression and Reconciliation in Cebus capucinus

Most data relating to aggressive and conciliatory behaviors are from Old World primates. We recorded agonistic interactions and post-conflict behaviors in a group of 12 white-faced capuchins (Cebus capucinus). After a conflict, we followed the aggressee as the focal individual during a 10-min postconflict period. We also conducted matched-control observations on the same individual. Conflicts involving physical contact were significantly bidirectional, and conflicts without physical contact were preferably unidirectional. Reconciliation was not be demonstrated at the group level. However, reconciliation occurred in kin and non-kin male/female dyads: their conciliatory tendencies were 48.1% and 21.2%, respectively. White-faced capuchins reconciled mainly during the first minutes after the end of the conflict. In kin and non-kin male/female dyads, selective attraction occurred, and aggressors were more likely to initiate affiliative contacts than aggressees. Hold-bottom and mount while emitting loud vocalizations were the most characteristic behaviors of reconciliation. Possible links may exist between aggressive and conciliatory patterns and other social variables.     

The proα2 (V) collagen gene (COL5A2) maps to 2q14→2q32, syntenic to the proα1 (III) collagen locus (COL3A1)

Summary A recombinant probe specific for the pro2 chain of human Type V collagen has been used for the localization of the corresponding gene (COL5A2) to chromosome 2. Regional mapping by in situ hybridization and analysis of DNA from humanxrodent cell lines indicated that COL5A2 is confined within the segment 2q142q32, thus syntenic to the pro1 (III) collagen gene (COL3A1).