ayout 1 - EMBL Grenoble

Cell Biology and Biophysics UnitDynamics of membrane traffickingPrevious and current researchMany biological processes at the cellular level are based on complex networks of macromolecularinteractions. These networks have modular organisation, where the modules form dynamic molecularmachines that drive processes such as signalling, cell motility, cytokinesis and vesicle trafficking.Our laboratory’s long-term goal is to contribute to the understanding of the generalprinciples governing the assembly and function of these supramolecular machines.More specifically, we are interested in the formation of cargo-loaded transport vesicles, such asendocytic vesicles. The formation of the endocytic vesicle is driven by a highly dynamic molecularmachinery composed of more than 50 different protein species and several thousand individualprotein molecules. Our main experimental organism is budding yeast, Saccharomyces cerevisiae.We combine powerful yeast genetics with quantitative live-cell imaging methods, with which wehave shown that the endocytic proteins assemble at the endocytic sites in a highly regulated sequenceand form modular machinery that drives vesicle formation. Using mutant yeast strains wehave revealed specific roles for numerous proteins in this process.Marko KaksonenPhD 2002, University ofHelsinki.Postdoctoral research at theUniversity of California,Berkeley.Group leader at EMBL since2006.Future projects and goalsIn the future, we will continue to study the membrane trafficking events in budding yeast using live-cell imaging combined with yeast genetics.We will focus on the mechanisms of the assembly of the clathrin-based endocytic machinery and the mechanisms of selective recruitment ofcargo molecules into the endocytic vesicle. We will also extend our work to trafficking events at the Golgi complex. These membrane traffickingevents are highly conserved elemental processes that are involved in multiple biological phenomena ranging from cell polarisation toneural plasticity. As most of the yeast trafficking proteins are widely conserved in eukaryotes, we believe that the mechanisms we unravel inyeast cells will be applicable to eukaryotes in general.A yeast cell expressing fluorescentlylabelledendocytic proteins. The firsttwo images show Sla1 (green) andAbp1 (red) proteins. The last imageshows both channels merged. Thespots at the cell surface revealaccumulation of the proteins atendocytic sites. The proteincomposition of endocytic machinerychanges dynamically during vesicleformation.Selected referencesKaksonen, M., Toret, C.P. & Drubin, D.G. (2006). Harnessing actindynamics for clathrin-mediated endocytosis. Nat. Rev. Mol. CellBiol., 7, 0-1Liu, J., Kaksonen, M., Drubin, D.G. & Oster, G. (2006). Endocyticvesicle scission by lipid phase boundary forces. Proc. Natl. Acad.Sci. USA, 103, 10277-82Kaksonen, M., Toret, C.P. & Drubin, D.G. (2005). A modular designfor the clathrin- and actin-mediated endocytosis machinery. Cell, 12,305-20Kaksonen, M., Sun, Y. & Drubin, D.G. (2003). A pathway forassociation of receptors, adaptors, and actin during endocyticinternalization. Cell, 2, 115, 75-8715