Analysis of galectin-3 induced plasma membrane reorganization in clathrin-independent endocytosis

• Applicant: Dr. Ulrike Becken
• Subject Area: Cell Biology
• Term: from 2012 to 2014
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 225942205

Endocytosis is a key mechanism by which eukaryotic cells receive information from their environment. One of the best characterized endocytic processes depends on the cytosolic clathrin coat. In recent years, it has become clear that clathrin-independent endocytic processes also exist. They are indispensable for a number of cellular functions such as signaling, migration and membrane homeostasis. With the exception of caveolae, coat-like structures could not be detected at sites of membrane invagination in these clathrin-independent processes, and it is not understood how proteins are sorted and what drives membrane curvature changes during carrier formation. The presented proposal focuses on the role of glycan binding galectin-3 in coat-independent cargo sorting and membrane curvature generation. Unpublished results from my host lab show that galectin-3 induces the formation of membrane invaginations into which galectin-3 cargo proteins are recruited. The process is glycosphingolipid-dependent and involves specific branched carbohydrates on cargo proteins. I will study the functional interplay of galectin-3, its plasma membrane receptors and glycosphingolipids microscopically and biochemically. I hypothesize that the galectin-3 dependent segregation of cargo proteins into domains on the plasma membrane is a prerequisite for their sorting into endocytic carriers. This hypothesis will be tested using fluorescence anisotropy imaging. I will then reconstitute galectin-3 driven membrane domain formation on model membranes. Thereby, I will test a model according to which the cargo-dependent recruitment of monomeric galectin-3 to membranes allows the formation of galectin-3 oligomers that then induce cargo-containing endocytic invaginations in a process requiring the membrane mechanical potential of glycosphingolipids. I expect that my work will substantially contribute to the understanding of mechanisms underlying clathrin-independent carrier formation and cargo sorting.

• DFG Programme: Research Fellowships
• International Connection: France
• Host: Professor Dr. Ludger Johannes