Neurexins are functional α-latrotoxin receptors

alpha-Latrotoxin is a potent neurotoxin that triggers synaptic exocytosis. Surprisingly, two distinct neuronal receptors for alpha-latrotoxin have been described: CIRL/latrophilin 1 (CL1) and neurexin-1 alpha, alpha-latrotoxin is thought to trigger exocytosis by binding to CL1,while the role of neurexin 1 alpha is uncertain. Using PC12 cells, we now demonstrate that neurexins indeed function as alpha-latrotoxin receptors that are at least as potent as CL1. Both alpha- and beta-neurexins represent autonomous alpha latrotoxin receptors that are regulated by alternative splicing. Similar to CL1, truncated neurexins without intracellular sequences are fully active; therefore, neurexins and CL1 recruit alpha-latrotoxin but are not themselves involved in exocytosis. Thus, alpha-latrotoxin is unique among neurotoxins, because it utilizes two unrelated receptors, probably to amplify recruitment of alpha-latrotoxin to active sites.