title: alpha-latrotoxin triggers transmitter release via direct insertion into the presynaptic plasma membrane.
abstract: alpha-latrotoxin, a component of black widow spider venom, binds to presynaptic nerve terminals and stimulates massive neurotransmitter release. Previous studies have demonstrated that alpha-latrotoxin first binds to two high-affinity receptors on nerve terminals, neurexins and CLs (CIRLs and latrophilins), and then executes a critical, second step of unknown nature that stimulates neurotransmitter release. We now demonstrate that incubation of alpha-latrotoxin with synaptosomes at 0 degrees C results in its peripheral membrane association. Incubation at 37 degrees C, however, converts the toxin into an operationally integral membrane protein, and induces generation of a protease-resistant fragment that consists of the entire N-terminal domain of alpha-latrotoxin and becomes protease sensitive after lysis of synaptosomes. Our data suggest that alpha-latrotoxin inserts into the presynaptic plasma membrane after receptor binding, resulting in an intracellular location of the N-terminal sequences. Membrane insertion of the N-terminal domain of alpha-latrotoxin occurs spontaneously, independently of membrane recycling or transmembrane ion gradients. We postulate that alpha-latrotoxin acts intracellularly in triggering release, and propose that non-selective cation channels induced by alpha-latrotoxin may be a by-product of membrane insertion.
authors.affiliation: Center for Basic Neuroscience, Department of Molecular Genetics and Howard Hughes Medical Institute, The University of Texas Southwestern Medical Center at Dallas, TX 75235, USA.
authors.forename: M
authors.initials: M
authors.lastname: Khvotchev
authors.forename: T C
authors.initials: TC
authors.lastname: Südhof
mesh_terms: D000818:Animals; D001692:Biological Transport; D002462:Cell Membrane / Q000187:drug effects; D006358:Hot Temperature; D006868:Hydrolysis; D051379:Mice; D010446:Peptide Fragments / Q000378:metabolism; D017729:Presynaptic Terminals / Q000187:drug effects*; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D013111:Spider Venoms / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D013574:Synaptosomes / Q000187:drug effects; D014357:Trypsin / Q000378:metabolism
chemical_list: D010446:Peptide Fragments; D011994:Recombinant Proteins; D013111:Spider Venoms; C020763:alpha-latrotoxin; D014357:Trypsin