Search

The hypothesis that neuropilin-1 (Npn-1) may interact with heparin-binding proteins other than vascular endothelial growth factor has been tested using an optical biosensor-based binding assay. The results show that fibroblast growth factor (FGF) 1, 2, 4, and 7, FGF receptor 1, hepatocyte growth factor/scatter factor (HGF/SF), FGF-binding protein, normal protease sensitive form of prion protein, antithrombin III, and Npn-1 itself are all able to interact with Npn-1 immobilized on the sensor surface. FGF-2, FGF-4, and HGF/SF are also shown to interact with Npn-1 in a solution assay. Moreover, these protein-protein interactions are dependent on the ionic strength of the medium and are inhibited by heparin, and the kinetics of binding of FGF-2, FGF-4 and HGF/SF to Npn-1 are characterized by fast association rate constants (270,000-1,600,000 m(-1) s(-1)). These results suggest that Npn-1 possesses a "heparin" mimetic site that is able to interact at least in part through ionic bonding with the heparin binding site on many of the proteins studied. Npn-1 was also found to potentiate the growth stimulatory activity of FGF-2 on human umbilical vein endothelial cells, indicating that Npn-1 may not just bind but also regulate the activity of heparin-binding proteins.

International audience; PURPOSE: Vascular endothelial growth factor (VEGF) and angiopoietins are key regulators of angiogenesis. The purpose of this study was to measure mRNA levels of these factors and of their receptors in surgically excised subfoveal membranes from patients with age-related macular degeneration (AMD) and to evaluate their relevance as prognostic markers of postsurgical recurrence of choroidal neovascularization (CNV). DESIGN: Prospective observational case series. METHODS: setting: Institutional. study population: In a prospective series of 24 patients (aged 51 to 91 years) with classic CNV of AMD diagnosed less than 6 months previously, 24 subfoveal membranes (one eye per patient) were surgically removed and collected. Thirteen patients underwent treatment for recurrence of CNV within 6 months of surgery. main outcome measures: Four 8-mu sections were prepared from each membrane for immunohistochemical determination of vascular density (CD31 immunostaining). The remaining tissue was used for preparation of total RNA. The levels of VEGF-A, VEGF-R1, VEGF-R2, neuropilin-1, angiopoietin-1, angiopoietin-2, Tie-2, and hypoxanthine phosphoribosyltransferase mRNAs were determined by real-time reverse-transcriptase polymerase chain reaction. RESULTS: Vascular endothelial growth factor, angiopoietin-1, and angiopoietin-2 appeared to be expressed to variable levels in most samples, whereas Tie-2, VEGF-R1, and VEGF-R2 were undetectable. Low levels of VEGF expression correlated with postsurgical recurrence of CNV (P = .07). Angiopoietin-1 and angiopoietin-2 levels did not predict recurrence (P > .1). CONCLUSION: The results indicate that at the time of surgical excision, subfoveal membranes express angiopoietin-1, VEGF, and, to a lesser degree, angiopoietin-2. Because CNV appears to recur less often in membranes expressing high levels of VEGF, we hypothesize that VEGF acts as a stabilizer of neovessels at this stage of the disease.

International audience; Previously, we demonstrated that loss of SEMA3F, a secreted semaphorin encoded in 3p21.3, is associated with higher stages in lung cancer and primary tumor cells studied with anti-vascular endothelial growth factor (VEGF) and SEMA3F antibodies. In vitro, SEMA3F inhibits cell spreading; this activity is opposed by VEGF. These results suggest that VEGF and SEMA3F compete for binding to their common neuropilin receptor. In the present report, we investigated the attractive/repulsive effects of SEMA3F on cell migration when cells were grown in a three-dimensional system and exposed to a SEMA3F gradient. In addition, we adapted the neurobiologic stripe assay to analyze the migration of tumor cells in response to SEMA3F. In the motile breast cancer cell line C100, which expresses both neuropilin-1 (NRP1) and neuropilin-2 (NRP2) receptors, SEMA3F had a repulsive effect, which was blocked by anti-NRP2 antibody. In less motile MCF7 cells, which express only NRP1, SEMA3F inhibited cell contacts with loss of membrane-associated E-cadherin and beta-catenin without motility induction. Cell spreading and proliferation were reduced. These results support the concept that in a first step during tumorigenesis, normal tissues expressing SEMA3F would try to prevent tumor cells from spreading and attaching to the stroma for further implantation.

International audience; Prostate cancer can usually be treated at a clinically localized stage by radical prostatectomy. Unfortunately, within 10 years following surgery, 30% of patients experience local or distant relapse. Few data exist on the association of markers of angiogenesis and distant relapse after radical prostatectomy. By immunohistochemistry in tissue microarray, we compared the expression pattern of hypoxia inducible factor 1, alpha subunit (HIF1α) and vascular endothelial growth factor (VEGF) and its receptors in 45 patients with distant relapse and 68 patients without relapse after radical prostatectomy. Expressions of HIF1α and VEGF were assessed in prostate tumor cells and those of VEGFR1, VEGFR2 and neuropilin 1 in tumor and endothelial cells. The five molecules studied were expressed by all tumors, with the exception of neuropilin 1 in endothelial cells for one tumor. Strong endothelial expression of VEGFR1 appeared to be an independent predictor of distant relapse. A moderate to strong endothelial expression of neuropilin 1 was in turn an independent predictor of absence of distant relapse. No significant difference was found for HIF1α, VEGF, VEGFR1, VEGFR2 and neuropilin 1 expression in tumor cells, nor for VEGFR2 in endothelial cells, between the two groups. To our knowledge, this is the first study to evaluate the prognostic value of VEGFR1, VEGFR2 and neuropilin 1 in endothelial cells in prostate cancer after radical prostatectomy. The evaluation by immunohistochemistry of endothelial expression of neuropilin 1 and VEGFR1 could be an additional tool in the assessment of tumor aggressiveness of clinically localized prostate cancer to better identify patients at high risk of distant relapse.

International audience; Minimal residual disease (MRD) has emerged as a major prognostic factor for monitoring patients with B-lineage acute lymphoblastic leukemia (B-ALL). The quantification of MRD by flow cytometry (FC) is based on the identification of a leukemia-associated phenotype (LAP). Because phenotypic switch is common during treatment, multiple LAPs must be available and used for MRD detection over time. We evaluated the potential usefulness of CD304 as a new marker for monitoring MRD. CD304 was expressed in 48% of B-ALL (24/50) with discriminative fluorescence intensity compared with CD304-negative normal B-cell precursors (n = 15). The sensitivity of CD304-based MRD detection reached 10(-4), as with some of established LAPs. The stability of CD304 expression evaluated during therapy and at relapse confirms the usefulness of this marker for MRD quantification. Finally, CD304 was repeatedly expressed in patients with TEL-AML1 gene rearrangement, which warrants further investigation on its potential relevance as a prognosis marker or therapeutic target.

International audience; Increased vascular permeability and vasodilation are responses usually elicited by snake envenomation. In this report, we isolated from Macroviperalebetina venom two protein groups designated IC1 (Increasing Capillary1) and IC2 based on their activities on capillary permeability. Mass spectrometry analysis showed that IC1 contained four major proteins of 23,650, 24,306, 24,589 and 24,718Da, whereas IC2 contained three major proteins of 25,101, 25,194 and 25,298Da. N-terminal amino-acid sequencing revealed that IC1 and IC2 belong to the snake venom VEGF (svVEGF) family. IC1 and IC2 had a marked specificity for VEGFR-2, with affinities in the nanomolar range. Interestingly, they also bind to NRP1 and NRP2, with affinities in the micromolar range. This is the first report demonstrating that M. lebetina encodes several distinct svVEGFs, endowed with a capacity to interact with neuropilins. IC1 and IC2 could be valuable tools to understand the molecular properties of angiogenic factors and their receptors.

International audience; An increasing body of evidence indicates that gene expression can be modulated by posttranscriptional mechanisms. RNA binding proteins, for instance, control gene expression at many regulatory levels including RNA splicing, transport, stability, and translation. Although numerous RNA binding proteins have been identified, very few have been studied extensively in the context of developmental processes. We focused our study on five neural RNA binding proteins: one Musashi homolog, Nrp-1, one member of the Bruno gene family, BruL-1 (also known as Etr-1), and three members of the ELAV/Hu family, ElrB, ElrC, and ElrD. As an initial step in addressing their function during Xenopus neurogenesis, we used in situ hybridization to determine their expression patterns during retinal development. We found that RNA binding proteins belonging to different families have distinct spatio-temporal expression. These combinatorial expression patterns are reminiscent of previously described cell type-specific expression patterns of transcription factors during retinal development. The distribution of RNA binding proteins within the retina suggests that these regulators of posttranscriptional events may play important roles in multiple steps of retinogenesis.

International audience; Neuropilin-1 (NRP1) is a receptor for the vascular endothelial growth factor (VEGF) family of angiogenesis factors and for the semaphorin family of secreted neuronal guidance polypeptides. Very little is known, however, about how NRP1 gene expression is regulated. In this study, it was demonstrated that the tumor promoter, TPA (12-O-tetradecanoylphorbol-13-acetate) significantly up-regulated NRP1 mRNA levels by increasing its gene transcription rate in a manner dependent on de novo protein synthesis. To determine which elements regulate functional NRP1 expression, the promoter regions of human and mouse NRP1 genes were cloned and characterized. Promoter-reporter gene transfection experiments using deletion and point mutations demonstrated that two Sp1 elements are major contributors to both the constitutive and TPA-induced activity of the NRP1 promoter. Gel shift analysis showed a specific binding of the Sp1 transcription factor to those elements. Further mutational analysis revealed that an AP-1, and a CCAAT box also contributed to NRP1 constitutive and TPA-induced promoter activity. It was concluded that NRP1 expression is regulated by the cooperation of several regulatory elements including AP-1, Sp1, and a CCAAT box.

International audience; The identity of the Human T lymphotropic Virus type 1 (HTLV-1) receptor remained an unsolved puzzle for two decades, until the recent demonstration that three molecules, Glucose Transporter 1, Neuropilin-1 and Heparan Sulfate Proteoglycans are involved in HTLV-1 binding and entry. Despite these advances, several questions remain unanswered, including the precise role of each of these molecules during virus entry. In light of the most recent data, we propose a model of the HTLV-1 receptor complex and discuss its potential impact on HTLV-1 infection.

Neurons, glia, and callosal axons operate as a “ménage à trois” in the development of the corpus callosum., The corpus callosum (CC) is the main pathway responsible for interhemispheric communication. CC agenesis is associated with numerous human pathologies, suggesting that a range of developmental defects can result in abnormalities in this structure. Midline glial cells are known to play a role in CC development, but we here show that two transient populations of midline neurons also make major contributions to the formation of this commissure. We report that these two neuronal populations enter the CC midline prior to the arrival of callosal pioneer axons. Using a combination of mutant analysis and in vitro assays, we demonstrate that CC neurons are necessary for normal callosal axon navigation. They exert an attractive influence on callosal axons, in part via Semaphorin 3C and its receptor Neuropilin-1. By revealing a novel and essential role for these neuronal populations in the pathfinding of a major cerebral commissure, our study brings new perspectives to pathophysiological mechanisms altering CC formation., Author Summary The largest commissural tract in the human brain is the corpus callosum, with over 200 million callosal axons that channel information between the two cerebral hemispheres. Failure of the corpus callosum to form appropriately is observed in several human pathologies and can result from defects during different steps of development, including cell proliferation, cell migration, or axonal guidance. Studies to date suggest that glial cells are critical for the formation of the corpus callosum. In this study, we show that during embryonic development, the corpus callosum, which was considered a neuron-poor structure, is in fact transiently populated by numerous glutamatergic and GABAergic neurons. With the use of in vitro graft experiments and of various transgenic mice, we demonstrate that neurons of the corpus callosum are essential for the accurate navigation of callosal axons. Moreover, we discovered that the guidance factor Semaphorin 3C, which is expressed by corpus callosum neurons, acts through the neuropilin 1 receptor to orient axons crossing through the corpus callosum. The present work therefore gives new insights into the mechanisms involved in axon guidance and implies that transient neurons work together with their glial partners in guiding callosal axons.