title: Differential abilities of SNAP-25 homologs to support neuronal function.
abstract: The SNAP receptor (SNARE) complex, consisting of synaptosome-associated protein of 25 kDa (SNAP-25), synaptobrevin-2, and syntaxin-1, is involved in synaptic vesicles exocytosis. In addition, SNAP-25 has been implicated in constitutive exocytosis processes required for neurite outgrowth. However, at least three isoforms of SNAP-25 have been reported from neurons: SNAP-23, which is also present in non-neuronal cells, and the two alternative splice variants SNAP-25a and SNAP-25b. Here, we studied the differential ability of these isoforms to support the functions previously broadly ascribed to "SNAP-25." We studied the rescue of snap-25 null neurons in culture with different SNAP-25 homologs. We find that deletion of SNAP-25 leads to strongly reduced neuron survival, and, in the few surviving cells, impaired arborization, reduced spontaneous release, and complete arrest of evoked release. Lentiviral expression of SNAP-25a, SNAP-25b, or SNAP-23 rescued neuronal survival, arborization, amplitude, and frequency of spontaneous events. Also evoked release was rescued by all isoforms, but synchronous release required SNAP-25a/b in both glutamatergic and GABAergic neurons. SNAP-23 supported asynchronous release only, reminiscent of synaptotagmin-1 null neurons. SNAP-25b was superior to SNAP-25a in vesicle priming, resembling the shift to larger releasable vesicle pools that accompanies synaptic maturation. These data demonstrate a differential ability of SNAP-25b, SNAP-25a, and SNAP-23 to support neuronal function.
authors.affiliation: Department of Membrane Biophysics, Max Planck Institute for Biophysical Chemistry, D-37077 Göttingen, Germany.
authors.forename: Ignacio
authors.initials: I
authors.lastname: Delgado-Martínez
authors.forename: Ralf B
authors.initials: RB
authors.lastname: Nehring
authors.forename: Jakob B
authors.initials: JB
authors.lastname: Sørensen
mesh_terms: D017398:Alternative Splicing / Q000502:physiology; D000704:Analysis of Variance; D000818:Animals; D002470:Cell Survival / Q000235:genetics; D002478:Cells, Cultured; D004307:Dose-Response Relationship, Radiation; D004558:Electric Stimulation / Q000379:methods; D004622:Embryo, Mammalian; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology / Q000528:radiation effects; D005786:Gene Expression Regulation / Q000502:physiology; D005822:Genetic Vectors / Q000502:physiology; D018698:Glutamic Acid / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology; D016086:Lentivirus / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D009474:Neurons / Q000502:physiology*; D018408:Patch-Clamp Techniques / Q000379:methods; D011726:Pyridinium Compounds / Q000378:metabolism; D050825:Synaptosomal-Associated Protein 25 / Q000172:deficiency / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: C508379:N-(3-trimethylammoniumpropyl)-4-(6-(4-(diethylamino)phenyl)hexatrienyl)pyridinium; D011726:Pyridinium Compounds; D050825:Synaptosomal-Associated Protein 25; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid