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Accueil > Départements > Biologie Cellulaire > Christien MERRIFIELD : Dynamique du Cytosquelette et Traffic Membranaire

Christien MERRIFIELD : Présentation de l’équipe

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The plasma membrane defines the surface of a cell and receptors - which are specialized proteins floating in the plasma membrane lipid bilayer - convey messages inside the cell to tell it to move, change shape, stick to neighbouring cells, divide or die. In order to regulate receptor signalling it is clearly important that cells carefully control the concentration of receptors in the plasma membrane and indeed the dysregulation of receptor trafficking underlies many disease states. Our lab is interested in the mechanism of endocytosis by which cells remove receptors from the plasma membrane. In one the most important types of endocytosis - referred to as clathrin mediated endocytosis - the endocytic machinery concentrates receptors into specialized patches which curve into 100nm membrane vesicles, coated with clathrin, which pinch off into the cell interior. To better understand the molecular choreography of clathrin mediated endocytosis we pioneered specialized imaging techniques using multi-colour total internal reflection fluorescence microscopy (TIRFM) to detect individual endocytic events in living cells while simultaneously measuring the arrival and departure of endocytic proteins (Merrifield et al., 2005). This allowed us to map out the molecular choreography of clathrin mediated endocytosis (Taylor et al., 2011) and to probe functional links between specific endocytic components (Taylor et al., 2012).

More recently we have adapted our experimental system to image single ligand-triggered endocytic events of medically relevant G-protein coupled receptors (GPCRs, such as beta-1-adrenergic receptor, Fig1) and receptor tyrosine kinases (RTKs) such as epidermal growth factor receptor (EGFr) at the level of single endocytic scission events in real time in living cells (Lampe et al., 2014). Using these highly sensitive and quantitative imaging techniques in combination with cell, molecular and biochemical techniques we are addressing the role played by the cytoskeleton in both constitutive and ligand-triggered endocytosis and the role played by the scission reaction itself in post-translational receptor modification and the signalling events conveyed by receptor cargos.

We are looking for motivated, creative and intellectually daring collaborators to join our lab at the I2BC Department of Cell Biology in Gif sur Yvette. A good grounding in cell biology, biochemistry, biophysics or experience with microscopy and image analysis would be helpful but natural curiosity coupled with a good, positive attitude and a willingness to learn are the most important attributes.

Fig1. Beta-1-adrenergic receptor internalizes through coated pits.
A. HEK-293 cell imaged using TIRF microscopy and expressing phluorin-beta-1-adrenergic receptor at pH7.4 (green, left panel) and 2s later at pH 5.2 (middle panel). Newly endocytosed vesicles appear as bright green spots at pH 5.2 colocalized with coated pits labelled with Mu2-mCherry (hollow arrows, right panel). Some vesicles uncoat but briefly remain close to the plasma membrane (solid arrows). B. Example scission event (upper panels, black arrow) and quantified fluorescence (lower graphs) showing phluorin-beta-1-adrenergic receptor signal at a coated pit at pH 7.4 (BAR7), pH 5.2 (BAR5) and Mu2-mCherry at pH 5.2 (Mu2-mCh). C. Time aligned and averaged fluorescence traces for a cohort of 500(+) events.

Contact


MERRIFIELD Christien [Chercheur - CNRS]
Equipe Merrifield C. - Dynamique du Cytosquelette et Traffic Membranaire [Responsable]
01 69 82 34 61 Gif - Bât 34

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