Design and expression of an ankyrin-like molecular probe for alpha-neurexin 1 labelling in live neurons

Neurexins (NRXNs) are a set of cell adhesion proteins that play a key role in the formation of new synaptic connections and pre-synaptic differentiation in the brain. NRXNs also participate in the remodeling of synapses terminals. Impairment of proper neurexin function can lead to psychological and developmental disorders, with recent evidence suggesting that they play a role in Alzheimer’s disease. Understanding the molecular mechanisms underlying neurexins alterations is paramount to shed light on their role in neurodegeneration. Current approaches to study NRXN’s function suffer from several limitations. In this project, we developed a molecular probe selective for α-neurexin 1 to label it in live cells by exploiting a neurotoxin found in the venom of Latrodectus spiders. First, we used a bioinformatics approach to identify the sequence of amino acids within a latrotoxin that binds to α-neurexin 1. This minimal sequence was used to design a peptide scaffold for our molecular probe. Then we generated two distinct expression vectors using molecular biology to express a recombinant sequence for selective probes and isolated them from a bacterial expression system. Finally, we assessed the selectivity and cytotoxicity of our recombinant probes in live cells containing α-NRXN 1. Overall, advancements were made on the development and activity assessment of novel approaches to study neurexins. Chapter 2 proposed a novel recognition sequence of latrotoxins to neurexin that up to date has not been identified. In chapter 3 we created modular expression plasmids enabling purification with metal chromatography to obtain a recombinant probe for neurexin. Finally, we showed that probe lost cytotoxic activity, but selectivity to neurexin still needs to be further assessed.