Abstract 1570 Design and Expression of an Ankyrin-like Molecular Probe for α-Neurexin 1 Labelling in Live Neurons

Neurexins (NRXNs) are a set of polymorphic cell adhesion molecules that play a key role in formation of new synaptic connections and pre-synaptic differentiation. Multiple binding partners for both α- and β- neurexins help shape the synaptic terminal and stablish stable connections between neurons. Additionally, NRXNs participate in remodelling of synapses terminal and the establishment of new connections. Impairment of proper neurexin function has been related to several psychological, developmental disorders and have been proposed to play a role in neurodegenerative pathogenesis in Alzheimer's disease alongside their post-synaptic counterpart neuroligin 1 (NLGN1). However, we lack the tools to study molecular mechanisms involving neurexins impairments in live cells without undergoing genetic engineering or heterologous gene expression. Herein we describe the development of a selective molecular probe for a-NRXN 1 to allow the real-time tracking of the receptor in live neurons. To achieve this, we used α-latrotoxin (α-LTX), a neurotoxin from the Latrodectus genus. Docking simulations were carried out to determine the binding domain to α-NRXN. We generated a bacterial recombinant expression vector to produce an ankyrin-like fragment of α-LTX. This α-LTX fragment was then used in transfected HEK 293 cells with α-NRXN 1 to measure binding selectivity and cytotoxicity. The final molecular probe offers a new approach for neurexin labelling in live cells to track its dynamic re-organization at synaptic termini during synaptic plasticity. This research was supported in part by the Natural Sciences and Engineering Research Council of Canada (NSERC 2020-06103) and the University of British Columbia. We gratefully thank UBC Okanagan College of Graduate Studies for active support and research scholarships.