title: A syntaxin-related protein controls acetylcholine release by different mechanisms in Aplysia.
abstract: Polyclonal antibodies raised against rat syntaxin-1B and an affinity-purified fraction have been used to study the functional role of this protein in transmitter release from Aplysia neurons. In a ganglionic protein extract, this fraction recognized a 37,000 molecular weight protein which therefore might be the Aplysia homologue of rat brain syntaxin-1B. Immunoglobulins were injected in the presynaptic cell of an identified cholinergic synapse of the buccal ganglion of Aplysia californica. This treatment decreased the postsynaptic response due to a reduction of the number of quanta released in relation to a decline of presynaptic Ca2+ current. When antibodies were applied extracellularly, transmitter release also decreased. In contrast to intracellular injection, this reduction was not accompanied by a decrease of the Ca2+ current but by an increase of presynaptic outward current. When injected in the presynaptic neuron, syntaxin complementary RNA also depressed Ca2+ current and transmission. This work provides evidence that Aplysia neurons express a syntaxin-like protein which is involved in the control of the presynaptic Ca2+ influx triggering acetylcholine release from terminals. This protein appears to have an extracellular segment which might interact with outward current.
mesh_terms: D000109:Acetylcholine / Q000378:metabolism*; D000200:Action Potentials / Q000502:physiology; D000818:Animals; D001048:Aplysia / Q000378:metabolism*; D015153:Blotting, Western; D004247:DNA / Q000096:biosynthesis; D005071:Evoked Potentials / Q000502:physiology; D017952:Ganglia, Invertebrate / Q000166:cytology / Q000378:metabolism; D008564:Membrane Potentials / Q000502:physiology; D008565:Membrane Proteins / Q000096:biosynthesis / Q000502:physiology*; D009419:Nerve Tissue Proteins / Q000096:biosynthesis / Q000502:physiology*; D009474:Neurons / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D050765:Qa-SNARE Proteins; D018075:RNA, Complementary / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D013569:Synapses / Q000187:drug effects / Q000378:metabolism
chemical_list: D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D050765:Qa-SNARE Proteins; D018075:RNA, Complementary; D012333:RNA, Messenger; D004247:DNA; D000109:Acetylcholine