Elucidating the Complexin C-terminal Domain Mechanism in Neurotransmission Regulation

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PROJECT SUMMARY Elucidating the Complexin C-terminal domain mechanism in neurotransmission regulation Dysregulation of neurotransmission underlies the neuropathophysiology of conditions like Alzheimer’s, Parkisons Disease, amyotrophic lateral sclerosis, and autism. Synaptic vesicle (SV) fusion is a central process in neurotransmission and SNARE (Soluble NSF Attachment Protein Receptor) proteins are essential to SV fusion, but the regulatory proteins of SNAREs are key to understanding the mechanisms. Despite fantastic research progress since the discovery of SNAREs, the mechanistic details driving SV fusion remain elusive. Complexin (Cpx) is a regulator of SNAREs and localizes to SVs via a curvature-sensing motif in its C-terminal domain (CTD). Strikingly, Cpx is highly conserved in the animal kingdom – even simple multicellular organisms lacking bona fide synapse like Trichoplax have Cpx. C. elegans lends itself as an ideal model organism to study Cpx biology as the mammalian Cpx null mutation is lethal. Furthermore, C.elegans is easy to image and provides a powerful genetic tool with its origins as a genetics model organism. Variants of Cpx have been reported to be pathogenic for infantile myoclonic epilepsy and intellectual disability (Redler, S. et al. Eur J Hum Genet 2017). Specifically, the CTD was mutated and the inefficient localization of complexin is thought to result in disease. Our research plan investigates whether the CTD is functionally essential to complexin and which mechanisms the complexin CTD employs in localizing to synaptic vesicles. In Aim 1, I will explore the role of the CPX-1 CTD in recruitment to specific vesicle pools at the synapse and target the N-terminal half of CPX-1 with foreign tethers to bypass CTD membrane binding. In Aim 2, I will characterize the features of the CTD curvature sensor required for efficient SV targeting and explore potential biochemical interactions between CPX-1 and the SV protein RAB-3. I will also explore several genes identified in a forward genetic suppressor screen of cpx-1 to extend my search of potential CPX- 1 binding partners. These aims will combine genetic, molecular, imaging, and biochemical approaches to dissect and characterize a critical region of Cpx, providing answers to a long-standing question on the synaptic mechanisms of Cpx. Under this fellowship, I will have the opportunity to work with leading researchers at the Tri-Institutional campus (Weill Cornell, Rockefeller, and Memorial Sloan Kettering) conducting neuroscience and biophysical research in a collaborative and supportive environment. To expand my technical skills and knowledge, I will attend workshops, seminars, and conferences on topics important for my research. Research findings will be shared with the scientific community and public via conferences and publications.