Drosophila AD3 mutation of synaptotagmin impairs calcium‐dependent self‐oligomerization activity

[摘要]

Genetic analysis of a Drosophila synaptotagmin (Syt) I mutant (AD3) has revealed that Tyr-334 within the C2B domain is essential for efficient Ca²⁺-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 Ca²⁺-dependent self-oligomerization activity mediated by the C2B domain but allows partial interaction with wild-type proteins in a Ca²⁺-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 Ca²⁺-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.

[学科分类] 生物化学/生物物理

[关键词] Synaptotagmin;C2 domain;Self-oligomerization;Exocytosis;Synaptic vesicle;HRP;horseradish peroxidase;IP4;D/L-myo-inositol 1;3;4;5-tetrakisphosphate;Syt(s);synaptotagmin(s)