Biomedical subjects

Julie Gavard

Publications and source records attributed to Julie Gavard.

11 recordsLinked to original sources

PubMed2006

VEGF controls endothelial-cell permeability by promoting the beta-arrestin-dependent endocytosis of VE-cadherin.

How vascular endothelial growth factor (VEGF) induces vascular permeability, its first described function, remains poorly understood. Here, we provide evidence of a novel signalling pathway by which VEGF stimulation promotes the rapid endocytosis of a key endothelial cell adhesion molecule, VE-cadherin, thereby disrupting the endothelial barrier function. This process is initiated by the activation of the small GTPase Rac by VEGFR-2 through the Src-dependent phosphorylation of Vav2, a guanine nucleotide-exchange factor. Rac activation, in turn, promotes the p21-activated kinase (PAK)-mediated phosphorylation of a highly conserved motif within the intracellular tail of VE-cadherin. Surprisingly, this results in the recruitment of beta-arrestin2 to serine-phosphorylated VE-cadherin, thereby promoting its internalization into clathrin-coated vesicles and the consequent disassembly of intercellular junctions. Ultimately, this novel biochemical route by which VEGF promotes endothelial permeability through the beta-arrestin2-dependent endocytosis of VE-cadherin may help identify new therapeutic targets for the treatment of many human diseases that are characterized by vascular leakage.

Amino Acid Sequence↗

PubMed2006

Regulation of cell-cell junctions by the cytoskeleton.

A major form of animal cell-cell adhesion results from the dynamic association of cadherin molecules, cytosolic catenins and actin microfilaments. Cadherins dynamically regulate the cytoskeleton. In turn, the actin cytoskeleton contributes to cadherin molecule oligomerization at cell contacts and to cell reshaping in response to environmental changes. Over the past two years, this evolutionarily conserved adhesion system has been intensively revisited in both its structural and functional aspects; this is illustrated by the remarkable progress in the determination of physical parameters of cadherin bonds (including force measurement) and the new insights into the role of alpha-catenin and the regulation of actin dynamics at cadherin contacts. Other recent studies uncover the important contribution of acto-myosin, microtubules and cell tension to adherens junction formation, cell differentiation and tissue reshaping/remodeling. An open challenge is now to integrate these new data with the diversity of cadherin adhesive complexes.

Actins↗

PubMed2006

A dileucine motif targets MCAM-l cell adhesion molecule to the basolateral membrane in MDCK cells.

Melanoma cell adhesion molecule (MCAM), an adhesion molecule belonging to the Ig superfamily, is an endothelial marker and is expressed in different epithelia. MCAM is expressed as two isoforms differing by their cytoplasmic domain: MCAM-l and MCAM-s (long and short). In order to identify the respective role of each MCAM isoform, we analyzed MCAM isoform targeting in polarized epithelial Madin-Darby canine kidney (MDCK) cells using MCAM-GFP chimeras. Confocal microscopy revealed that MCAM-s and MCAM-l were addressed to the apical and basolateral membranes, respectively. Transfection of MCAM-l mutants established that a single dileucine motif (41-42) of the cytoplasmic domain was required for MCAM-l basolateral targeting in MDCK cells. Although double labelling experiments showed that MCAM-l is not a component of adherens junctions and focal adhesions, its expression on basolateral membranes suggests that MCAM-l is involved in epithelium insuring.

Amino Acid Motifs↗

PubMed2005

Tetanus neurotoxin-mediated cleavage of cellubrevin impairs epithelial cell migration and integrin-dependent cell adhesion.

A role for endocytosis and exocytosis in cell migration has been proposed but not yet demonstrated. Here, we show that cellubrevin (Cb), an early endosomal v-SNARE, mediates trafficking in the lamellipod of migrating epithelial cells and partially colocalizes with markers of focal contacts. Expression of tetanus neurotoxin, which selectively cleaves Cb, significantly reduced the speed of migrating epithelial cells. Furthermore, expression of tetanus neurotoxin enhanced the adhesion of epithelial cells to collagen, laminin, fibronectin, and E-cadherin; altered spreading on collagen; and impaired the recycling of beta1 integrins. These results suggest that Cb-dependent membrane trafficking participates in cell motility through the regulation of cell adhesion.

Animals↗

PubMed2005

A novel function for cadherin-11 in the regulation of motor axon elongation and fasciculation.

We previously observed that cadherin-11, a type II cadherin, is expressed in growing motor and sensory axons in the mouse embryo. Here, we assessed its functional involvement in the regulation of axon elongation and fasciculation by evaluating the activity of a specific cadherin-11 homophilic ligand, cad11-Fc (cadherin-11 extracellular region fused to Fc fragment of IgG), on the length and organization of motor axons outgrowing from embryonic ventral spinal cord explants. Cad11-Fc substrate enhanced axon growth and prevented interactions occurring between growing axons, providing evidences for a role of cadherin-11 in the control of growth cone progression. Comparison of cadherin-11 with N-cadherin, a type I cadherin concomitantly expressed by motor axons, revealed similarities in their functional properties, including the ability to reorganize the actin cytoskeleton through interactions with catenins, but differences in their axon growth-promoting activity, arguing for subtle differences in their contributions to peripheral nerve elongation.

Animals↗

PubMed2005

Once upon a time there was beta-catenin in cadherin-mediated signalling.

beta-Catenin was initially characterized as a protein interacting with the cadherin cytoplasmic tail and regulating cell-cell contacts and actin cytoskeleton interactions. Moreover, the gene coding for the Drosophila orthologue of beta-catenin, armadillo, was independently identified downstream of wingless in the segment-polarity signalling pathway. In fact, beta-catenin/Armadillo turned out to be key mediators of the Wnt/Wingless pathways in vertebrates and invertebrates. beta-Catenin participates in both adhesion and signalling functions in a mutually exclusive manner; bound to cadherins at the plasma membrane or 'unbound' in cytosolic or nuclear complexes. This model had placed beta-catenin at the crossroads between cadherin and Wnt signalling, leading to the dogma of inhibition of beta-catenin signalling by cadherins.

Animals↗

PubMed2004

Clustering of cellular prion protein induces ERK1/2 and stathmin phosphorylation in GT1-7 neuronal cells.

The physiological role of the prion protein is largely unknown. Here, clustering of prion at the surface of GT1-7 cells was observed upon anti-prion antibody treatments. This clustering was associated with a rapid and transient phosphorylation of the mitogen activated protein kinases (MAPKs) extracellular receptor kinases 1 and 2 (ERK1/2), and also of the microtubule-destabilizing protein stathmin at serine 16. The specificity of this antibody-mediated activation was ascertained by its inhibition by prion small interfering RNA. The phosphorylation of ERK1/2 but not that of stathmin was abolished by the MAPK/ERK kinase 1 inhibitor U0126, whereas both signaling pathways were blocked by the specific inhibitor of the epidermal growth factor receptor AG1478, suggesting the likely recruitment of this receptor upon prion clustering.

Animals↗

PubMed2004

N-cadherin activation substitutes for the cell contact control in cell cycle arrest and myogenic differentiation: involvement of p120 and beta-catenin.

N-cadherin is expressed throughout skeletal myogenesis and has been proposed to be involved in the differentiation program of myogenic precursors. Here, we further characterize the N-cadherin involvement and its mechanism of action at the onset of differentiation, through controlled N-cadherin activation by plating isolated C2 myoblasts on surfaces coated with a chimeric Ncad-Fc homophilic ligand (N-cadherin ectodomain fused to the immunoglobulin G Fc fragment). We show that N-cadherin activation substitutes for the cell density in myogenic differentiation by promoting myogenin and troponin T expression. In addition, N-cadherin adhesion participates to the associated cell cycle arrest through the nuclear accumulation of cyclin-dependent kinase inhibitors p21 and p27. Mouse primary myoblast cultures exhibited similar responses to N-cadherin as C2 cells. RNA interference knockdowns of the N-cadherin-associated cytoplasmic proteins p120 and beta-catenin produced opposite effects on the differentiation pathway. p120 silencing resulted in a decreased myogenic differentiation, associated with a reduction in cadherin-catenin content, which may explain its action on myogenic differentiation. beta-Catenin silencing led to a stimulatory effect on myogenin expression, without any effect on cell cycle. Our results demonstrate that N-cadherin adhesion may account for cell-cell contact-dependent cell cycle arrest and differentiation of myogenic cells, involving regulation through p120 and beta-catenins.

Animals↗

PubMed2004

[Regulation of cell adhesion by the cadherin cytoplasmic domain].

Juxtacrine cell interactions associated to cadherin-mediated cell-cell adhesion play a major role in the organization and homeostasis of tissues. Here, we review the intracellular molecules and regulations controlling the formation of cell-cell contacts initiated by homophilic interactions of cadherin ectodomain. These regulations involve proteins associated to cadherin cytoplasmic tail, named catenins, their association to the actin cytoskeleton and the stability of these complexes at the cell membrane. The underlying molecular mechanisms, which participate in the formation of dynamic cell-cell contacts, are intensively investigated.

Actins↗

PubMed2003

Lamellipodium extension and cadherin adhesion: two cell responses to cadherin activation relying on distinct signalling pathways.

Cell adhesion molecules of the cadherin family contribute to the regulation of cell shape and fate by mediating strong intercellular adhesion through Ca2+-dependent interaction of their ectodomain and association of their cytoplasmic tail to actin. However, the mechanisms co-ordinating cadherinmediated adhesion with the reorganization of the actin cytoskeleton remain elusive. Here, the formation of de novo contacts was dissected by spreading cells on a highly active N-cadherin homophilic ligand. Cells responded to N-cadherin activation by extending lamellipodium and organizing cadherin-catenin complexes and actin filaments in cadherin adhesions. Lamellipodium protrusion, associated with actin polymerization at the leading edge sustained the extension of cadherin contacts through a phosphoinositide 3-kinase (PI 3-kinase)-Rac1 pathway. Cadherin adhesions were formed by PI 3-kinase-independent, Rac1-dependent co-recruitment of adhesion complexes and actin filaments. The expression and localization of p120 at the plasma membrane, associated with an increase in membrane-associated Rac1 was required for both cell responses, consistent with a major role of p120 in signalling pathways initiated by cadherin activation and contributing to Rac1-dependent contact extension and maturation. These results provide additional information on the mechanisms by which cadherin coordinates adhesion with dynamic changes in the cytoskeleton to control cell shape and intercellular junction organization.

Animals↗

PubMed2002

Cadherin-based cell adhesion in neuromuscular development.

The organisation and differentiation of striated skeletal muscles and their innervation is a particularly complex process implicating cells of mesodermic (myoblasts and fibroblasts) and neuroectoderrmic origin (neurons and glial cells). Myogenic and motor neuron precursors, the two major cell types participating in the formation of the neuromuscular axis, migrate, segregate, reassociate and differentiate in a coordinated fashion. The subsequent organisation of muscle cells and the establishment of muscle innervation rely on a complex tissular and cellular architectural organisation, which cannot be understood without taking into account juxtacrine cell interactions, and especially cell adhesion. Cell adhesion receptors of the cadherin family are widely expressed and dynamically regulated in space and time throughout neuromuscular development. A single cell expresses in general more than one cadherin at its surface and it is the combination of these molecules and their level of expression that determine their action within a given cell population. We focused in this review on the expression and roles of classical cadherins in relation to muscle cell and motoneuron differentiation. We also review the latest results on the mode of action of cadherins allowing to propose cellular and molecular cues on the mechanisms by which these cell adhesion receptors control muscle and neuronal cell shape, migration and differentiation.

Animals↗