Molecular Structure and Engineering of Synaptic Organizer Proteins in Health and Disease

Synapses are the specialized cellular junctions that form the basic units of communication between neuronal cells. Given the variety of network-dependent functions that synapses need to support, a fundamental question is how their properties are specified at the molecular level. Membrane-anchored and soluble “synaptic organizer proteins” form adhesive interactions that mediate synapse formation and differentiation. However, a structural and mechanistic understanding of how they recruit and organize the molecular machinery for neurotransmission is largely lacking. Simultaneously, dysfunction of synapses and loss of neurons are hallmarks of neurodegenerative disease that underlie a persistent deterioration of cognitive functions. The properties of synaptic organizer proteins to form and functionalize synapses could be exploited as a mechanism for synaptic repair to reverse neuronal degeneration.The aims of this proposal are (i) to reveal the structural basis for trans-synaptic molecular nanocolumn formation by determining the complex structures of synaptic organizer proteins and neurotransmitter receptors, and (ii) to leverage insights into the structure and function of soluble synaptic organizers for generating engineered variants that can remodel synapses with the potential for restoring neuronal circuitry and cognition in animal models of Alzheimer’s disease (AD), the most common form of dementia associated with early defects in synaptic function. To achieve these aims, I will combine techniques of structural biology (X-ray crystallography, cryo-electron microscopy and biophysical interaction analysis), protein engineering (combinatorial screening using yeast surface display), and cellular neuroscience (neuronal culture, electrophysiology, advanced imaging and mouse models). Our results will elucidate fundamental principles of synaptic signalling and pave the way for disease-modifying therapies that focus on recovery of synaptic connectivity and function.