title: Drosophila AD3 mutation of synaptotagmin impairs calcium-dependent self-oligomerization activity.
abstract: Genetic analysis of a Drosophila synaptotagmin (Syt) I mutant (AD3) has revealed that Tyr-334 within the C2B domain is essential for efficient Ca(2+)-dependent neurotransmitter release. However, little is known as to why a missense mutation (Tyr-334-Asn) disrupts the function of the C2B domain at the molecular level. Here, we present evidence that a Tyr-312 to Asn substitution in mouse Syt II, which corresponds to the Drosophila AD3 mutation, completely impairs Ca(2+)-dependent self-oligomerization activity mediated by the C2B domain but allows partial interaction with wild-type proteins in a Ca(2+)-dependent manner. This observation is consistent with the fact that the AD3 allele is homozygous lethal but complements another mutant phenotype. We also showed that the Ca(2+)-dependent C2B self-oligomerization is inhibited by inositol 1,3,4, 5-tetrakisphosphate, a potent inhibitor of neurotransmitter release. All of these findings strongly support the idea that self-oligomerization of Syt I or II is essential for neurotransmitter release in vivo.
authors.affiliation: Laboratory for Developmental Neurobiology, Brain Science Institute, Saitama, Japan. mfukuda@brain.riken.go.jp
authors.forename: M
authors.initials: M
authors.lastname: Fukuda
authors.forename: H
authors.initials: H
authors.lastname: Kabayama
authors.forename: K
authors.initials: K
authors.lastname: Mikoshiba
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001704:Biopolymers / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins; D004330:Drosophila / Q000235:genetics; D007295:Inositol Phosphates / Q000494:pharmacology; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D050857:Synaptotagmins; D014443:Tyrosine / Q000235:genetics / Q000378:metabolism
chemical_list: D001704:Biopolymers; D002135:Calcium-Binding Proteins; D007295:Inositol Phosphates; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; C116606:inositol-1,2,4,5-tetrakisphosphate; D050857:Synaptotagmins; D014443:Tyrosine; D002118:Calcium