Brain function crucially depends on chemical neurotransmission at synapses, while, conversely, synaptic dysfunction underlies neurological and psychiatric disorders. Synapses are composed of more than 2,000 distinct proteins, spatially organized into specialized molecular machineries. During decades of efforts, researchers have acquired a wealth of knowledge on individual key components of the synapse. However, the overall picture of the spatial arrangement, molecular architecture and interaction network of the synaptic proteome remains largely uncharted. Furthermore, innovative methods that allow system-wide profiling of these organizational aspects of synaptic proteins are in great demand. I propose to develop a highly sensitive cross-linking mass spectrometry (XL-MS) pipeline to analyze structural and organizational features of the synaptic proteome at an unprecedented depth and comprehensiveness. In parallel, I also plan to establish quantitative XL-MS strategies to reveal global network rearrangements and complex-specific alterations during long-term potentiation, which arguably is the most attractive cellular model for learning and memory. Importantly, it is foreseeable that numerous novel insights can be discovered, for which I will use complementary approaches and tools, such as biochemistry, super-resolution imaging, structural modelling and network analysis to validate and interrogate their molecular details and network principles. These studies will yield groundbreaking insights into the molecular architecture of the synapse and thereby fill a crucial knowledge gap in neuroscience. Furthermore, they will provide a framework to gain a deeper understanding of the dynamic regulation in synaptic plasticity and synaptic dysfunction in neurological disorders.

Our ability to move, to process sensory information or to form, store and retrieve memories crucially depends on the function of neuronal synapses. Synapses comprise a presynaptic compartment harboring the machinery for neurotransmitter release and an associated postsynaptic compartment that processes the neurotransmitter signal. During decades of research we have acquired a wealth of knowledge regarding the mechanisms of neurotransmitter release and information processing in the postsynaptic compartment. In great contrast, we know surprisingly little about the pathways that direct the formation, transport, and assembly of the complex molecular machines that make up a functional presynapse. In particular, it is unclear where and how synaptic vesicle (SV) precursors are formed in the neuronal cell body, in which form they are transported along the axon, and which maturation steps occur to allow their assembly into functional units for neurotransmitter release. How cytoplasmically synthesized presynaptic active zone (AZ) proteins that organize SV release sites are transported and assembled is equally unclear. Here, we combine genome engineering in stem cell-derived neurons and genetically altered mice with proteomic, high-resolution imaging and systems biology approaches to identify the origin and composition of SV and AZ precursors, dissect the mechanisms of their axonal transport and integration into developing synapses and unravel the pathway that controls axonal transport and presynaptic assembly of newly made SV and AZ proteins to set synaptic weight. Our high risk/ high gain studies will yield groundbreaking insights into the mechanisms that mediate the formation, maintenance, and dynamic remodeling of the presynaptic compartment during development and thereby fill a crucial knowledge gap in neuroscience. Furthermore, they may pave the way for the future development of therapeutics to cure nerve injury or neurological disorders linked to synapse dysfunction.

Chiral molecules are characterized by specific stereo arrangements of their nuclei underlying their key function in chemistry and biology. Yet, little is known about chiral molecular interactions at the level of electrons, occurring on the ultrafast time scale. Developing extremely efficient enantio-sensitive ultrafast all-optical approaches to track electronic dynamics is an important unsolved challenge. We aim to address it in ULISSES – a multidisciplinary project at the interface of physical chemistry, strong-field physics, ultrafast and nonlinear optics. We plan to take advantage of the chiral electron currents, which arise naturally in chiral molecules interacting with sufficiently intense ultrafast light. The chiral nature of these currents is dictated by the molecule itself. We will structure laser polarization in space and time, endowing light with local chiral and global topological properties, to control these electron currents, enabling new, orders of magnitude more efficient, enantio-sensitive all-optical effects, gaining access to the ultrafast electron dynamics and physical mechanisms underlying the chiral function. We will also develop a framework for describing geometrical magnetism, generated by the electron currents in chiral molecules, and introduce a new class of enantio-sensitive phenomena enabled by these geometric concepts. We aim to establish: 1) novel, highly efficient, all-optical ways of enantio-discrimination, 2) enantio-resolved movies of chiral electronic dynamics, 3) chiral topological light – a new tool for chiral interactions, and 4) bridges between light-driven electron dynamics in chiral gases and topological effects in solids. ULISSES will dramatically expand fundamental understanding of the dynamical response of chiral systems to light and lay the foundation for innovative applications of all-optical methods to chiral discrimination in low-density samples with extraordinary sensitivity and molecular specificity.