ERC FUNDED PROJECTS

Autophagy is a catabolic pathway that delivers cytoplasmic material to lysosomes for degradation. Under vegetative conditions, the pathway serves as quality control system, specifically targeting damaged or superfluous organelles and protein-aggregates. Cytotoxic stresses and starvation, however, induces the formation of larger autophagosomes that capture cargo unselectively. Autophagosomes are being generated from a cup-shaped precursor membrane, the isolation membrane, which expands to engulf cytoplasmic components. Sealing of this structure gives rise to the double-membrane surrounded autophagosomes. Two interconnected ubiquitin (Ub)-like conjugation systems coordinate the expansion of autophagosomes by conjugating the autophagy related (Atg)-protein Atg8 to the isolation membrane. In an effort to unravel the function of Atg8, we reconstituted the system on model membranes in vitro and found that Atg8 forms together with the Atg12–Atg5-Atg16 complex a membrane scaffold which is required for productive autophagy in yeast. Humans possess seven Atg8-homologs and two mutually exclusive Atg16-variants. Here, we propose to investigate the function of the human Ub-like conjugation system using a fully reconstituted in vitro system. The spatiotemporal organization of recombinant fluorescent-labeled proteins with synthetic model membranes will be investigated using confocal and TIRF-microscopy. Structural information will be obtained by atomic force and electron microscopy. Mechanistic insights, obtained from the in vitro work, will be tested in vivo in cultured human cells. We belief that revealing 1) the function of the human Ub-like conjugation system in autophagy, 2) the functional differences of Atg8-homologs and the two Atg16-variants Atg16L1 and TECPR1 and 3) how Atg16L1 coordinates non-canonical autophagy will provide essential insights into the pathophysiology of cancer, neurodegenerative, and autoimmune diseases.

1 499 726 €

Start date: 2015-04-01, End date: 2020-03-31

Developing brain implants is crucial to better decipher the neuronal information and intervene in a very thin way on neural networks using microstimulations. This project aims to address two major challenges: to achieve the realization of a highly mechanically stable implant, allowing long term connection between neurons and microelectrodes and to provide neural implants with a high temporal and spatial resolution. To do so, the present project will develop implants with structural and mechanical properties that resemble those of the natural brain environment. According to the literature, using electrodes and electric leads with a size of a few microns allows for a better neural tissue reconstruction around the implant. Also, the mechanical mismatch between the usually stiff implant material and the soft brain tissue affects the adhesion between tissue cells and electrodes. With the objective to implant a highly flexible free-floating microelectrode array in the brain tissue, we will develop a new method using micro-nanotechnology steps as well as a combination of polymers. Moreover, the literature and preliminary studies indicate that some surface chemistries and nanotopographies can promote neurite outgrowth while limiting glial cell proliferation. Implants will be nanostructured so as to help the neural tissue growth and to be provided with a highly adhesive property, which will ensure its stable contact with the brain neural tissue over time. Implants with different microelectrode configurations and number will be tested in vitro and in vivo for their biocompatibility and their ability to record and stimulate neurons with high stability. This project will produce high-performance generic implants that can be used for various fundamental studies and applications, including neural prostheses and brain machine interfaces.

1 499 850 €

Start date: 2015-08-01, End date: 2021-07-31

Following their synthesis during DNA replication, sister chromatids remain paired by the cohesin complex, which forms the basis for their faithful segregation during cell division. Cohesin is a large ring-shaped protein complex, incorporating an ABC-type ATPase module. Despite its importance for genome stability, the molecular mechanism of cohesin action remains as intriguing as it remains poorly understood. How is cohesin topologically loaded onto chromatin? How is it unloaded again? What happens to cohesin during DNA replication in S-phase, so that it establishes cohesion between newly synthesized sister chromatids? We propose to capitalise on our recent success in the biochemical reconstitution of topological cohesin loading onto DNA. This lays the foundation for a work programme encompassing a combination of biochemical, single molecule, structural and genetic approaches to address the above questions. Five work packages will investigate cohesin’s molecular behaviour during its life-cycle on chromosomes, including the ATP binding and hydrolysis-dependent conformational changes that make this molecular machine work. It will be complemented by mechanistic analyses of the cofactors that help cohesin to load onto chromosomes and establish sister chromatid cohesion. The insight gained will not only advance our molecular knowledge of sister chromatid cohesion. It will more generally advance our understanding of the ubiquitous family of chromosomal SMC ATPases, of which cohesin is a member, and their activity of shaping and segregating genomes.

2 120 100 €

Start date: 2015-10-01, End date: 2020-09-30

The unexpected connection between the primary cilium and cell-to-cell signalling is one of the most exciting discoveries in cell and developmental biology in the last decade. In particular, the Hedgehog (Hh) pathway relies on the primary cilium to fulfil its fundamental functions in orchestrating vertebrate development. This microtubule-based antenna, up to 5 µm long, protrudes from the plasma membrane of almost every human cell and is the essential compartment for the entire Hh signalling cascade. All its molecular components, from the most upstream transmembrane Hh receptor down to the ultimate transcription factors, are dynamically localised and enriched in the primary cilium. The aim of this proposal, which combines structural biology and live cell imaging, is to understand the function and signalling consequences of the multivalent interactions between Hh signal transducer proteins as well as their spatial and temporal regulation in the primary cilium. The key questions my laboratory will address are: What are the rules for assembly of Hh signal transduction complexes? How dynamic are these complexes in size and organisation? How are these processes linked to the transport and accumulation in the primary cilium? I will combine state-of-the art structural biology techniques (with an emphasis on X-ray crystallography) to study the molecular architecture of binary and higher-order Hh signal transduction complexes and live cell fluorescence microscopy (for protein localisation and direct protein interactions). These two approaches will allow me to identify and define specific protein-protein interfaces at the atomic level and test their functional consequences in the cell in real time. My goal is to consolidate a world-class morphogen signal transduction laboratory, deciphering fundamental biological insights. Importantly, my results and reagents can potentially feed into the development of novel anti-cancer therapeutics and reagents promoting stem cell therapy.

1 727 456 €

Start date: 2015-08-01, End date: 2020-07-31