ERC FUNDED PROJECTS

Despite the discovery of amyloidosis more than a century ago, the molecular and cellular mechanisms of these devastating human disorders remain obscure. In addition to their involvement in disease, amyloid fibrils perform physiological functions, whilst others have potentials as biomaterials. To realise their use in nanotechnology and to enable the development of amyloid therapies, there is an urgent need to understand the molecular pathways of amyloid assembly and to determine how amyloid fibrils interact with cells and cellular components. The challenges lie in the transient nature and low population of aggregating species and the panoply of amyloid fibril structures. This molecular complexity renders identification of the culprits of amyloid disease impossible to achieve using traditional methods. Here I propose a series of exciting experiments that aim to cast new light on the molecular and cellular mechanisms of amyloidosis by exploiting approaches capable of imaging individual protein molecules or single protein fibrils in vitro and in living cells. The proposal builds on new data from our laboratory that have shown that amyloid fibrils (disease-associated, functional and created from de novo designed sequences) kill cells by a mechanism that depends on fibril length and on cellular uptake. Specifically, I will (i) use single molecule fluorescence and non-covalent mass spectrometry and to determine why short fibril samples disrupt biological membranes more than their longer counterparts and electron tomography to determine, for the first time, the structural properties of cytotoxic fibril ends; (ii) develop single molecule force spectroscopy to probe the interactions between amyloid precursors, fibrils and cellular membranes; and (iii) develop cell biological assays to discover the biological mechanism(s) of amyloid-induced cell death and high resolution imaging and electron tomography to visualise amyloid fibrils in the act of killing living cells.

2 498 465 €

Start date: 2013-05-01, End date: 2019-04-30

Arl (Arf-like) proteins, GTP-binding proteins of the Ras superfamily, are molecular switches that cycle between a GDP-bound inactive and GTP-bound active state. There are 16 members of the Arl subfamily in the human genome whose basic mechanistic function is unknown. The interactome of Arl2/3 includes proteins involved in retinopathies and other ciliary diseases such as Leber¿s Congenital Amaurosis (LCA) and kidney diseases such as nephronophthisis. Arl6 has been found mutated in Bardet Biedl Syndrome, another pleiotropic ciliary disease. In the proposed interdisciplinary project I want to explore the function of the protein network of Arl2/3 and Arl6 by a combination of biochemical, biophysical and structural methods and use the knowledge obtained to probe their function in live cells. As with other subfamily proteins of the Ras superfamily which have been found to mediate similar biological functions I want to derive a basic understanding of the function of Arl proteins and how it relates to the development and function of the ciliary organelle and how they contribute to ciliary diseases. The molecules in the focus of the project are: the GTP-binding proteins Arl2, 3, 6; RP2, an Arl3GAP mutated in Retinitis pigmentosa; Regulators of Arl2 and 3; PDE¿ and HRG4, effectors of Arl2/3, which bind lipidated proteins; RPGR, mutated in Retinitis pigmentosa, an interactor of PDE¿; RPGRIP and RPGRIPL, interactors of RPGR mutated in LCA and other ciliopathies; Nephrocystin, mutated in nephronophthisis, an interactor of RPGRIP and Arl6, mutated in Bardet Biedl Syndrome, and the BBS complex. The working hypothesis is that Arl protein network(s) mediate ciliary transport processes and that the GTP switch cycle of Arl proteins is an important element of regulation of these processes.

2 434 400 €

Start date: 2011-04-01, End date: 2016-03-31

Autophagy is a conserved, lysosomal-mediated pathway required for cell homeostasis and survival. It is controlled by the master regulators of energy (AMPK) and growth (TORC1) and mediated by the ATG (autophagy) proteins. Deregulation of autophagy is implicated in cancer, immunity, infection, aging and neurodegeneration. Autophagosomes form and expand using membranes from the secretory and endocytic pathways but how this occurs is not understood. ATG9, the only transmembrane ATG protein traffics through the cell in vesicles, and is essential for rapid initiation and expansion of the membranes which form the autophagosome. Crucially, how ATG9 functions is unknown. I will determine how ATG9 initiates the formation and expansion of the autophagosome by amino acid starvation through a molecular dissection of proteins resident in ATG9 vesicles which modulate the composition and property of the initiating membrane. I will employ high resolution light and electron microscopy to characterize the nucleation of the autophagosome, proximity-specific biotinylation and quantitative Mass Spectrometry to uncover the proteome required for the function of the ATG9, and optogenetic tools to acutely regulate signaling lipids. Lastly, with our tools and knowledge I will develop an in vitro reconstitution system to define at a molecular level how ATG9 vesicle proteins, membranes that interact with ATG9 vesicles, and other accessory ATG components nucleate and form an autophagosome. In vitro reconstitution of autophagosomes will be assayed biochemically, and by correlative light and cryo-EM and cryo-EM tomography, while functional reconstitution of autophagy will be tested by selective cargo recruitment. The development of a reconstituted system and identification proteins and lipids which are key components for autophagosome formation will provide a means to identify a new generation of targets for translational work leading to manipulation of autophagy for disease related therapies.

2 121 055 €

Start date: 2018-07-01, End date: 2023-06-30

The functioning of a single cell or organism is governed by the laws of chemistry and physics. The bridge from biology to chemistry and physics is provided by structural biology: to understand the functioning of a cell, it is necessary to know the atomic structure of macromolecular assemblies, which may contain hundreds of components. To characterise the structures of the increasingly large and often flexible complexes, high resolution structure determination (as was possible for example for the ribosome) will likely stay the exception, and multiple sources of structural data at multiple resolutions are employed. Integrating these data into one consistent picture poses particular difficulties, since data are much more sparse than in high resolution methods, and the data sets from heterogeneous sources are of highly different and unknown quality and may be mutually inconsistent, and that data are in general averaged over large ensembles and long times. Molecular modelling, a crucial element of any structure determination, plays an even more important role in these multi-scale and multi-technique approaches, not only to obtain structures from the data, but also to evaluate their reliability. This proposal is to develop a consistent framework for this highly complex data integration problem, principally based on Bayesian probability theory. Appropriate models for the major types data types used in hybrid approaches will be developed, as well as representations to include structural knowledge for the components of the complexes, at multiple scales. The new methods will be applied to a series of problems with increasing complexity, going from the determination of protein complexes with high resolution information, over low resolution structures based on protein-protein interaction data such as the nuclear pore, to the genome organisation in the nucleus.

2 130 212 €

Start date: 2012-05-01, End date: 2017-04-30