Valérie Chambon

Publications (4)93.09 Total impact

• Source

  Available from: Laetitia Pontani

  Article: Actin dynamics drive membrane reorganization and scission in clathrin-independent endocytosis.

  Winfried Römer, Léa-Laetitia Pontani, Benoît Sorre, Carles Rentero, Ludwig Berland, Valérie Chambon, Christophe Lamaze, Patricia Bassereau, Cécile Sykes, Katharina Gaus, Ludger Johannes
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  ABSTRACT: Nascent transport intermediates detach from donor membranes by scission. This process can take place in the absence of dynamin, notably in clathrin-independent endocytosis, by mechanisms that are yet poorly defined. We show here that in cells scission of Shiga toxin-induced tubular endocytic membrane invaginations is preceded by cholesterol-dependent membrane reorganization and correlates with the formation of membrane domains on model membranes, suggesting that domain boundary forces are driving tubule membrane constriction. Actin triggers scission by inducing such membrane reorganization process. Tubule occurrence is indeed increased upon cellular depletion of the actin nucleator component Arp2, and the formation of a cortical actin shell in liposomes is sufficient to trigger the scission of Shiga toxin-induced tubules in a cholesterol-dependent but dynamin-independent manner. Our study suggests that membranes in tubular Shiga toxin-induced invaginations are poised to undergo actin-triggered reorganization leading to scission by a physical mechanism that may function independently from or in synergy with pinchase activity.
  Cell 02/2010; 140(4):540-53. · 32.40 Impact Factor
• Source

  Available from: Günter Schwarzmann

  Article: GM1 structure determines SV40-induced membrane invagination and infection.

  Helge Ewers, Winfried Römer, Alicia E Smith, Kirsten Bacia, Serge Dmitrieff, Wengang Chai, Roberta Mancini, Jürgen Kartenbeck, Valérie Chambon, Ludwig Berland, Ariella Oppenheim, Günter Schwarzmann, Ten Feizi, Petra Schwille, Pierre Sens, Ari Helenius, Ludger Johannes
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  ABSTRACT: Incoming simian virus 40 (SV40) particles enter tight-fitting plasma membrane invaginations after binding to the carbohydrate moiety of GM1 gangliosides in the host cell plasma membrane through pentameric VP1 capsid proteins. This is followed by activation of cellular signalling pathways, endocytic internalization and transport of the virus via the endoplasmic reticulum to the nucleus. Here we show that the association of SV40 (as well as isolated pentameric VP1) with GM1 is itself sufficient to induce dramatic membrane curvature that leads to the formation of deep invaginations and tubules not only in the plasma membrane of cells, but also in giant unilamellar vesicles (GUVs). Unlike native GM1 molecules with long acyl chains, GM1 molecular species with short hydrocarbon chains failed to support such invagination, and endocytosis and infection did not occur. To conceptualize the experimental data, a physical model was derived based on energetic considerations. Taken together, our analysis indicates that SV40, other polyoma viruses and some bacterial toxins (Shiga and cholera) use glycosphingolipids and a common pentameric protein scaffold to induce plasma membrane curvature, thus directly promoting their endocytic uptake into cells.
  Nature Cell Biology 12/2009; 12(1):11-8; sup pp 1-12. · 19.49 Impact Factor
• Article: Analysis of articulation between clathrin and retromer in retrograde sorting on early endosomes.

  Vincent Popoff, Gonzalo A Mardones, Siau-Kun Bai, Valérie Chambon, Danièle Tenza, Patricia V Burgos, Anbing Shi, Philippe Benaroch, Sylvie Urbé, Christophe Lamaze, Barth D Grant, Graça Raposo, Ludger Johannes
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  ABSTRACT: Clathrin and retromer have key functions for retrograde trafficking between early endosomes and the trans-Golgi network (TGN). Previous studies on Shiga toxin suggested that these two coat complexes operate in a sequential manner. Here, we show that the curvature recognition subunit component sorting nexin 1 (SNX1) of retromer interacts with receptor-mediated endocytosis-8 (RME-8) protein, and that RME-8 and SNX1 colocalize on early endosomes together with a model cargo of the retrograde route, the receptor-binding B-subunit of Shiga toxin (STxB). RME-8 has previously been found to bind to the clathrin uncoating adenosine triphosphatase (ATPase) Hsc70, and we now report that depletion of RME-8 or Hsc70 affects retrograde trafficking at the early endosomes-TGN interface of STxB and the cation-independent mannose 6-phosphate receptor, an endogenous retrograde cargo protein. We also provide evidence that retromer interacts with the clathrin-binding protein hepatocyte growth factor-regulated tyrosine kinase substrate (Hrs) not only via SNX1, as previously published (Chin Raynor MC, Wei X, Chen HQ, Li L. Hrs interacts with sorting nexin 1 and regulates degradation of epidermal growth factor receptor. J Biol Chem 2001;276:7069-7078), but also via the core complex component Vps35. Hrs codistributes at the ultrastructural level with STxB on early endosomes, and interfering with Hrs function using antibodies or mild overexpression inhibits retrograde transport. Our combined data suggest a model according to which the functions in retrograde sorting on early endosomes of SNX1/retromer and clathrin are articulated by RME-8, and possibly also by Hrs.
  Traffic 10/2009; 10(12):1868-80. · 4.92 Impact Factor
• Source

  Available from: Vincent Fraisier

  Article: Shiga toxin induces tubular membrane invaginations for its uptake into cells.

  Winfried Römer, Ludwig Berland, Valérie Chambon, Katharina Gaus, Barbara Windschiegl, Danièle Tenza, Mohamed R E Aly, Vincent Fraisier, Jean-Claude Florent, David Perrais, Christophe Lamaze, Graça Raposo, Claudia Steinem, Pierre Sens, Patricia Bassereau, Ludger Johannes
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  ABSTRACT: Clathrin seems to be dispensable for some endocytic processes and, in several instances, no cytosolic coat protein complexes could be detected at sites of membrane invagination. Hence, new principles must in these cases be invoked to account for the mechanical force driving membrane shape changes. Here we show that the Gb3 (glycolipid)-binding B-subunit of bacterial Shiga toxin induces narrow tubular membrane invaginations in human and mouse cells and model membranes. In cells, tubule occurrence increases on energy depletion and inhibition of dynamin or actin functions. Our data thus demonstrate that active cellular processes are needed for tubule scission rather than tubule formation. We conclude that the B-subunit induces lipid reorganization that favours negative membrane curvature, which drives the formation of inward membrane tubules. Our findings support a model in which the lateral growth of B-subunit-Gb3 microdomains is limited by the invagination process, which itself is regulated by membrane tension. The physical principles underlying this basic cargo-induced membrane uptake may also be relevant to other internalization processes, creating a rationale for conceptualizing the perplexing diversity of endocytic routes.
  Nature 12/2007; 450(7170):670-5. · 36.28 Impact Factor