The molecular organization of the synapse
Information processing in the brain relies on the accuracy of synapses to encode information. We investigate how key protein machineries that enable accuracy in synaptic transmission are assembled and structurally organized. The ultimate goal is to apply this fundamental knowledge to design efficient strategies to enhance information processing across the brain.
main scientific questions
structural organization of neurotransmitter release sites
The active zone is the protein machinery that defines the sites for the release of neurotransmitters from synaptic vesicles. This machinery is divided into distinct complexes; one to cluster Ca2+ channels of the Cav2 family and one to generate priming sites for synaptic vesicles.
The relative abundance and relative position of these two complexes must define the neurotransmission capacity of a synapse. We look for the key proteins and protein interactions that determine the formation and the subsynaptic positioning of these complexes.
assembly of the synaptic endocytic apparatus
The endocytic apparatus restores synaptic vesicles after exocytosis at the periactive zone, which is the membrane area adjacent to the active zone. We investigate the mechanisms that assemble this machinery at the periactive zone. This is important because endocytosis at synapses is executed orders of magnitude faster than in non-neuronal cells, indicating that specialized assembly pathways exist.
We also investigate the structural organization of this apparatus. It is unknown whether all endocytic proteins operate in a single complex or whether, like at the active zone, independent complexes formed by subsets of them exist. This is of relevance given the diversity of release requirements across synapses, which may be matched by specialized endocytic complexes.
molecular tools to enhance information transmission
We build on the molecular principles of assembly of the active zone and endocytic machineries to develop molecular strategies that lead to enhancing synaptic transmission. Tools that modulate neurotransmission have the potential to overcome the transmission deficits underlying the symptomatology of neurological disorders.
An example of a pathway that we pursue is Liprin-α, which contributes to priming site assembly. Selective intervention on the interactions between Liprin-α and presynaptic scaffolds can lead to enhanced synaptic strength.
We will use mouse genetics to target specific proteins and transmitter systems, superresolution microscopy to assess the organization of protein machineries, electron microscopy for synapse ultrastructure, electrophysiology and functional imaging to assess synapse functionality, live imaging for protein dynamics, and molecular biology and biochemistry to assess protein interactions and proteins behaviors.
main technical approaches
From left to right: inhibitory postsynaptic currents evoked by a train of action potentials; electron micrograph of a synapse; synapse imaged in 10X Expansion Microscopy stained against the postsynaptic marker PSD-95 (blue) and the active zone proteins Liprin-α (red) and Munc13-1 (green); superresolution image of a Calyx of Held stained against the synaptic vesicle marker Synaptophysin (grey), the active zone protein Bassoon (magenta) and the endocytic protein PIPK1; and generation of liquid condensates triggered by phosphorylation of Liprin-α3.