Kaksonen Group

A yeast cell expressing fluorescently-labelled endocytic proteins. The first two images show Sla1 (green)and Abp1 (red)proteins. The last image shows both channels merged. The spots at the cell surface reveal accumulation of the proteins at endocytic sites. The protein composition of endocytic machinery changes dynamically during vesicle formation.

Previous and current research

Many biological processes at the cellular level are based on complex networks of macromolecular interactions. These networks have modular organisation, where the modules form dynamic molecular machines 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 general principles governing the assembly and function of these supramolecular machines.

More specifically, we are interested in the formation of cargo-loaded transport vesicles, such as endocytic vesicles. The formation of the endocytic vesicle is driven by a highly dynamic molecular machinery composed of more than 50 different protein species and several thousand individual protein molecules. Our main experimental organism is budding yeast, Saccharomyces cerevisiae. We combine powerful yeast genetics with quantitative live-cell imaging methods, with which we have shown that the endocytic proteins assemble at the endocytic sites in a highly regulated sequence and form modular machinery that drives vesicle formation. Using mutant yeast strains we have revealed specific roles for numerous proteins in this process.

Future projects and goals

In 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 of cargo molecules into the endocytic vesicle. We will also extend our work to trafficking events at the Golgi complex. These membrane trafficking events are highly conserved elemental processes that are involved in multiple biological phenomena ranging from cell polarisation to neural plasticity. As most of the yeast trafficking proteins are widely conserved in eukaryotes, we believe that themechanisms we unravel in yeast cells will be applicable to eukaryotes in general.