108 research outputs found
Rab11-FIP3 is a cell cycle-regulated phosphoprotein
No full text<b>BACKGROUND:</b>
Rab11 and its effector molecule, Rab11-FIP3 (FIP3), associate with recycling endosomes and traffic into the furrow and midbody of cells during cytokinesis. FIP3 also controls recycling endosome distribution during interphase. Here, we examine whether phosphorylation of FIP3 is involved in these activities.<p></p>
<b>RESULTS:</b>
We identify four sites of phosphorylation of FIP3 in vivo, S-102, S-280, S-347 and S-450 and identify S-102 as a target for Cdk1-cyclin B in vitro. Of these, we show that S-102 is phosphorylated in metaphase and is dephosphorylated as cells enter telophase. Over-expression of FIP3-S102D increased the frequency of binucleate cells consistent with a role for this phospho-acceptor site in cytokinesis. Mutation of S-280, S-347 or S-450 or other previously identified phospho-acceptor sites (S-488, S-538, S-647 and S-648) was without effect on binucleate cell formation and did not modulate the distribution of FIP3 during the cell cycle. In an attempt to identify a functional role for FIP3 phosphorylation, we report that the change in FIP3 distribution from cytosolic to membrane-associated observed during progression from anaphase to telophase is accompanied by a concomitant dephosphorylation of FIP3. However, the phospho-acceptor sites identified here did not control this change in distribution.<p></p>
<b>CONCLUSIONS:</b>
Our data thus identify FIP3 as a cell cycle regulated phosphoprotein and suggest dephosphorylation of FIP3 accompanies its translocation from the cytosol to membranes during telophase. S102 is dephosphorylated during telophase; mutation of S102 exerts a modest effect on cytokinesis. Finally, we show that de/phosphorylation of the phospho-acceptor sites identified here (S-102, S-280, S-347 and S-450) is not required for the spatial control of recycling endosome distribution or function
Midbody inheritance, degradation and functions
No full textCitokinesis is a final stage of cell division, during which, the mother cell divides, leaving two newly formed daughter cells connected by a thin intercellular bridge (ICB). During abscission of this ICB, the central spindle microtubules are compacted into a protein-rich structure, known as a midbody (MB). Until recently, it was thought that post-mitotic MBs are discarded into the extracellular space where they are degraded immediately following cytokinesis. However, recent studies have shown that MBs are prone to accumulate and persist for a long time in cancer stem cell and cancer cell populations, indi-cating that it may have some post-mitotic functions. Furthermore, it was shown that post-mitotic MBs might function as signalling platforms and determine the stemness and aggressiveness of cancer cells. The abscission of the ICB can occur on one side of the MB (asymmetric abscission), leading to the inheritance of post-mitotic MB only by one daughter cell. Alternatively, when ICB is cut on both sides of the MB (symmetric abscission), the MB is discarded into the extracellular space where it is gradually degraded or internalized by the surrounding cells. The functional consequences of inherited post-mitotic MB in comparison with internalized extracellular post-mitotic MB remains undetermined. How cells retain, accumulate and degrade post-mitotic MB, remains elusive. Although the post-mitotic MB functions become clearer over time, there is still no clear definition of how these intercellular structures accumulate and get degraded once they are inherited or internalized by cancer cells. Moreover, the mechanisms governing post-mitotic MB internalization as well as functional consequences of MB accumulation to cancer cells proliferation and oncogenic potential still need to be determined
The Art of “Cut and Run”: The Role of Rab14 GTPase in Regulating N-Cadherin Shedding and Cell Motility
No full textLinford et al. define a Rab14-mediated endocytic recycling pathway that controls proteolytic N-cadherin cleavage by transporting ADAM10 protease to the plasma membrane. When this pathway is disrupted, diminished ADAM10-dependent N-cadherin shedding leads to increased cell-cell adhesion and inhibition of cell motility
Polarité cellulaire et morphogenèse / Cell polarity and morphogenesis
No full textSéminaire FSER organisé par André Le Bivic (IBDM, Marseille, France) et Daniel St Johnston (The Gurdon Institute, University of Cambridge, UK) du 25 juin au 30 juin 2018 Participants Jean-Paul Borg, Arnaud Echard, Nathan Goehring, André Le Bivic, Pierre-François Lenne, Ian G. Macara, Jean-Léon Maître, Sophie Martin, Fernando Martín-Belmonte, Mireille Montcouquiol, Edwin Munro, Caren Norden, Ewa Paluch, Rytis Prekeris, Josana Rodriguez, Bénédicte Sanson, Daniel St Johnston, Ulrich Tepass, John..
Cytocinèse, l’étape finale de la division cellulaire / Cytokinesis, the final step of cell division
No full textSéminaire FSER organisé par Arnaud Echard (Institut Pasteur, Paris, France) du 2 au 7 avril 2018 Participants Renata Basto, William Bement, Julie C. Canman, Jeremy Carlton, Arnaud Echard, Ulrike Eggert, Christine Field, Daniel Gerlich, Mariagrazia Giansanti, Michael Glotzer, Gilles Hickson, Carsten Janke, Péter Lénárt, Juan Martin-Serrano, Juliette Mathieu, Thomas Müller-Reichert, Karen Oegema, Rytis Prekeris, Aurélien Roux, Anne Royou Et Héloïse Dufour (Cercle FSER) pour la matinée « Meeting..
Rabs, Rips, FIPs, and Endocytic Membrane Traffic
No full textRab GTPases, proteins belonging to the Ras-like small GTP-binding protein superfamily, have emerged as master regulators of cellular membrane transport. Rab11 GTPase, a member of the Rab protein family, plays a role in regulating various cellular functions, including plasma membrane recycling, phagocytosis, and cytokinesis. Rab11 acts by forming mutually exclusive complexes with Rab11-family binding proteins, known as FIPs. Rab11-FIP complexes serve a role of �targeting complexes� by recruiting various membrane traffic factors to cellular membranes. Recent studies have identified several Rab11-FIP complex-binding proteins that regulate distinct membrane traffic pathways
Regulation of ESCRT-III assembly and membrane scission activity in the budding yeast Saccharomyces cerevisiae
No full textThe sequential recruitment and assembly of endosomal sorting complexes required for transport (ESCRTs) at the endosomal membrane mediate the selection and clustering of cargoes into vesicles that bud into the lumen of the endosome. In addition to regulating this sorting process at endosomes, in mammalian cells ESCRTs are additionally required for the budding of many types of enveloped viruses, as well as the separation of cells during cytokinesis. These processes share a topologically similar membrane scission event facilitated by regulated ESCRT-III assembly at the cytoplasmic surface of the membrane to promote the formation and scission of internal vesicles. The Snf7 subunit of ESCRT-III in yeast binds directly to an auxiliary protein, Bro1. Like ESCRT-III, Bro1 is required for the formation of intralumenal vesicles at endosomes, but its role in membrane scission has remained uncharacterized. We show that overexpression of Bro1, or its N-terminal Bro1 domain that binds Snf7, enhances the stability of ESCRT-III. Bro1 binding to the Snf7 subunit of ESCRT-III additionally inhibits Vps4-mediated disassembly of ESCRT-III complexes in vivo and in vitro. This stabilization effect correlates with a reduced frequency in the budding of intralumenal vesicles within endosomes, and the appearance of vesicle budding profiles, vesicles that have not yet separated from the limiting endosomal membrane, as observed by electron microscopy and 3-D electron tomography. These results implicate Bro1 as a regulator of ESCRT-III assembly state, and additionally suggest that Vps4-mediated disassembly of the ESCRT-III complex is important for vesicle membrane scission. We also observed that deletion of ESCRT-III proteins Snf7 or Vps24, or overexpression of Bro1 or the Bro1 domain causes the accumulation of budded yeast cells by flow cytometry. While these proteins have been shown to participate in cell abscission in mammalian cells, a role for these proteins in cell division has not been established in yeast. Our findings suggest that ESCRT-III and Bro1 participate in the abscission step of cytokinesis in yeast, implicating them as conserved effectors of membrane scission
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