Nicolas Taulet

Publications of Nicolas Taulet

• Light-Activated Regulation of Cofilin Dynamics Using a Photocaged Hydrogen Peroxide Generator.

  Authors: Evan W Miller, Nicolas Taulet, Carl S Onak, Elizabeth J New, Julie K Lanselle, Gillian S Smelick, Christopher J Chang

  Journal of the American Chemical Society. 11/2010;

  Hydrogen peroxide (H(2)O(2)) can exert diverse signaling and stress responses within living systems depending on its spatial and temporal dynamics. Here we report a new small-molecule probe forHydrogen peroxide (H(2)O(2)) can exert diverse signaling and stress responses within living systems depending on its spatial and temporal dynamics. Here we report a new small-molecule probe for producing H(2)O(2) on demand upon photoactivation and its application for optical regulation of cofilin-actin rod formation in living cells. This chemical method offers many potential opportunities for dissecting biological roles for H(2)O(2) as well as remote control of cell behavior via H(2)O(2)-mediated pathways.

• A novel and specific NADPH oxidase-1 (Nox1) small-molecule inhibitor blocks the formation of functional invadopodia in human colon cancer cells.

  Authors: Davide Gianni, Nicolas Taulet, Hui Zhang, Celine DerMardirossian, Jeremy Kister, Luis Martinez, William R Roush, Steven J Brown, Gary M Bokoch, Hugh Rosen

  ACS chemical biology. 10/2010; 5(10):981-93.

  The NADPH oxidase (Nox) proteins catalyze the regulated formation of reactive oxygen species (ROS), which play key roles as signaling molecules in several physiological and pathophysiologicalThe NADPH oxidase (Nox) proteins catalyze the regulated formation of reactive oxygen species (ROS), which play key roles as signaling molecules in several physiological and pathophysiological processes. ROS generation by the Nox1 member of the Nox family is necessary for the formation of extracellular matrix (ECM)-degrading, actin-rich cellular structures known as invadopodia. Selective inhibition of Nox isoforms can provide reversible, mechanistic insights into these cellular processes in contrast to scavenging or inhibition of ROS production. Currently no specific Nox inhibitors have been described. Here, by high-throughput screening, we identify a subset of phenothiazines, 2-acetylphenothiazine (here referred to as ML171) (and its related 2-(trifluoromethyl)-phenothiazine) as nanomolar, cell-active, and specific Nox1 inhibitors that potently block Nox1-dependent ROS generation, with only marginal activity on other cellular ROS-producing enzymes and receptors including the other Nox isoforms. ML171 also blocks the ROS-dependent formation of ECM-degrading invadopodia in colon cancer cells. Such effects can be reversed by overexpression of Nox1 protein, which is suggestive of a selective mechanism of inhibition of Nox1 by this compound. These results elucidate the relevance of Nox1-dependent ROS generation in mechanisms of cancer invasion and define ML171 as a useful Nox1 chemical probe and potential therapeutic agent for inhibition of cancer cell invasion.

• c-Src-mediated phosphorylation of NoxA1 and Tks4 induces the reactive oxygen species (ROS)-dependent formation of functional invadopodia in human colon cancer cells.

  Authors: Davide Gianni, Nicolas Taulet, Céline DerMardirossian, Gary M Bokoch

  Molecular biology of the cell. 10/2010; 21(23):4287-98.

  The NADPH oxidase family, consisting of Nox1-5 and Duox1-2, catalyzes the regulated formation of reactive oxygen species (ROS). Highly expressed in the colon, Nox1 needs the organizer subunit NoxO1The NADPH oxidase family, consisting of Nox1-5 and Duox1-2, catalyzes the regulated formation of reactive oxygen species (ROS). Highly expressed in the colon, Nox1 needs the organizer subunit NoxO1 and the activator subunit NoxA1 for its activity. The tyrosine kinase c-Src is necessary for the formation of invadopodia, phosphotyrosine-rich structures which degrade the extracellular matrix (ECM). Many Src substrates are invadopodia components, including the novel Nox1 organizer Tks4 and Tks5 proteins. Nox1-dependent ROS generation is necessary for the maintenance of functional invadopodia in human colon cancer cells. However, the signals and the molecular machinery involved in the redox-dependent regulation of invadopodia formation remain unclear. Here, we show that the interaction of NoxA1 and Tks proteins is dependent on Src activity. Interestingly, the abolishment of Src-mediated phosphorylation of Tyr110 on NoxA1 and of Tyr508 on Tks4 blocks their binding and decreases Nox1-dependent ROS generation. The contemporary presence of Tks4 and NoxA1 unphosphorylable mutants blocks SrcYF-induced invadopodia formation and ECM degradation, while the overexpression of Tks4 and NoxA1 phosphomimetic mutants rescues this phenotype. Taken together, these results elucidate the role of c-Src activity on the formation of invadopodia and may provide insight into the mechanisms of tumor formation in colon cancers.

• N-cadherin/P120 catenin association at cell-cell contacts occurs in cholesterol-rich membrane domains and is required for rhoa activation and myogenesis.

  Authors: Nicolas Taulet, Franck Comunale, Cyril Favard, Sophie Charrasse, Stephane Bodin, Cecile Gauthier-Rouviere

  The Journal of biological chemistry. 07/2009;

  p120 catenin is a major regulator of cadherin stability at cell-cell contacts and a modulator of Rho GTPase activities. In C2C12 myoblasts, N-cadherin is stabilized at cell contacts through itsp120 catenin is a major regulator of cadherin stability at cell-cell contacts and a modulator of Rho GTPase activities. In C2C12 myoblasts, N-cadherin is stabilized at cell contacts through its association with cholesterol-rich membrane domains or lipid rafts (LR) and acts as an adhesion-activated receptor which activates RhoA, an event required for myogenesis induction. Here, we report that association of p120 catenin with N-cadherin at cell contacts occurs specifically in LR. We demonstrate that interaction of p120 catenin with N-cadherin is required for N-cadherin association with LR and for its stabilization at cell contacts. LR disruption inhibits myogenesis induction and N-cadherin-dependent RhoA activation as does the perturbation of the N-cadherin/p120 catenin complex after p120 catenin knockdown. Finally, we observe a N-cadherin-dependent accumulation of RhoA at PI(4,5)P2-enriched cell contacts which is lost after LR disruption. Thus, a functional N-cadherin/catenins complex occurs in cholesterol-rich membrane microdomains that allows the recruitment of RhoA and the regulation of its activity during myogenesis induction.

• Novel p47(phox)-related organizers regulate localized NADPH oxidase 1 (Nox1) activity.

  Authors: Davide Gianni, Begoña Diaz, Nicolas Taulet, Bruce Fowler, Sara A Courtneidge, Gary M Bokoch

  Science signaling. 01/2009; 2(88):ra54.

  The mechanisms that determine localized formation of reactive oxygen species (ROS) through NADPH (reduced form of nicotinamide adenine dinucleotide phosphate) oxidase (Nox) family members inThe mechanisms that determine localized formation of reactive oxygen species (ROS) through NADPH (reduced form of nicotinamide adenine dinucleotide phosphate) oxidase (Nox) family members in nonphagocytic cells are unknown. We show that the c-Src substrate proteins Tks4 (tyrosine kinase substrate with four SH3 domains) and Tks5 are functional members of a p47(phox)-related organizer superfamily. Tks proteins selectively support Nox1 and Nox3 (and not Nox2 and Nox4) activity in reconstituted cellular systems and interact with the NoxA1 activator protein through an Src homology 3 domain-mediated interaction. Endogenous Tks4 is required for Rac guanosine triphosphatase- and Nox1-dependent ROS production by DLD1 colon cancer cells. Our results are consistent with the Tks-mediated recruitment of Nox1 to invadopodia that form in DLD1 cells in a Tks- and Nox-dependent fashion. We propose that Tks organizers represent previously unrecognized members of an organizer superfamily that link Nox to localized ROS formation.

• Rac1 and RhoA GTPases have antagonistic functions during N-cadherin-dependent cell-cell contact formation in C2C12 myoblasts.

  Authors: Franck Comunale, Marie Causeret, Cyril Favard, Julien Cau, Nicolas Taulet, Sophie Charrasse, Cécile Gauthier-Rouvière

  Biology of the cell / under the auspices of the European Cell Biology Organization. 10/2007; 99(9):503-17.

  BACKGROUND INFORMATION: N-cadherin, a member of the Ca(2+)-dependent cell-cell adhesion molecule family, plays an essential role in the induction of the skeletal muscle differentiation programme.BACKGROUND INFORMATION: N-cadherin, a member of the Ca(2+)-dependent cell-cell adhesion molecule family, plays an essential role in the induction of the skeletal muscle differentiation programme. However, the molecular mechanisms which govern the formation of N-cadherin-dependent cell-cell contacts in myoblasts remain unexplored. RESULTS: In the present study, we show that N-cadherin-dependent cell contact formation in myoblasts is defined by two stages. In the first phase, N-cadherin is highly mobile in the lamellipodia extensions between the contacting cells. The second stage corresponds to the formation of mature N-cadherin-dependent cell contacts, characterized by the immobilization of a pool of N-cadherin which appears to be clustered in the interdigitated membrane structures that are also membrane attachment sites for F-actin filaments. We also demonstrated that the formation of N-cadherin-dependent cell-cell contacts requires a co-ordinated and sequential activity of Rac1 and RhoA. Rac1 is involved in the first stage and facilitates N-cadherin-dependent cell-cell contact formation, but it is not absolutely required. Conversely, RhoA is necessary for N-cadherin-dependent cell contact formation, since, via ROCK (Rho-associated kinase) signalling and myosin 2 activation, it allows the stabilization of N-cadherin at the cell-cell contact sites. CONCLUSIONS: We have shown that Rac1 and RhoA have opposite effects on N-cadherin-dependent cell-cell contact formation in C2C12 myoblasts and act sequentially to allow its formation.

• N-cadherin association with lipid rafts regulates its dynamic assembly at cell-cell junctions in C2C12 myoblasts.

  Authors: Marie Causeret, Nicolas Taulet, Franck Comunale, Cyril Favard, Cécile Gauthier-Rouvière

  Molecular biology of the cell. 06/2005; 16(5):2168-80.

  Cadherins are homophilic cell-cell adhesion molecules implicated in cell growth, differentiation, and organization into tissues during embryonic development. They accumulate at cell-cell contactCadherins are homophilic cell-cell adhesion molecules implicated in cell growth, differentiation, and organization into tissues during embryonic development. They accumulate at cell-cell contact sites and act as adhesion-activated signaling receptors. Here, we show that the dynamic assembly of N-cadherin at cell-cell contacts involves lipid rafts. In C2C12 myoblasts, immunofluorescence and biochemical experiments demonstrate that N-cadherin present at cell-cell contacts is colocalized with lipid rafts. Disruption of lipid rafts leads to the inhibition of cell-cell adhesion and disorganization of N-cadherin-dependent cell-cell contacts without modifying the association of N-cadherin with catenins and its availability at the plasma membrane. Fluorescent recovery after photobleaching experiments demonstrate that at the dorsal plasma membrane, lipid rafts are not directly involved in the diffusional mobility of N-cadherin. In contrast, at cell-cell junctions N-cadherin association with lipid rafts allows its stabilization enabling the formation of a functional adhesive complex. We show that lipid rafts, as homophilic interaction and F-actin association, stabilize cadherin-dependent adhesive complexes. Homophilic interactions and F-actin association of N-cadherin are both required for its association to lipid rafts. We thus identify lipid rafts as new regulators of cadherin-mediated cell adhesion.