Nonet M L, Saifee O, Zhao H, Rand J B, Wei L
Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
J Neurosci. 1998 Jan 1;18(1):70-80. doi: 10.1523/JNEUROSCI.18-01-00070.1998.
Synaptobrevins are vesicle-associated proteins implicated in neurotransmitter release by both biochemical studies and perturbation experiments that use botulinum toxins. To test these models in vivo, we have isolated and characterized the first synaptobrevin mutants in metazoans and show that neurotransmission is severely disrupted in mutant animals. Mutants lacking snb-1 die just after completing embryogenesis. The dying animals retain some capability for movement, although they are extremely uncoordinated and incapable of feeding. We also have isolated and characterized several hypomorphic snb-1 mutants. Although fully viable, these mutants exhibit a variety of behavioral abnormalities that are consistent with a general defect in the efficacy of synaptic transmission. The viable mutants are resistant to the acetylcholinesterase inhibitor aldicarb, indicating that cholinergic transmission is impaired. Extracellular recordings from pharyngeal muscle also demonstrate severe defects in synaptic transmission in the mutants. The molecular lesions in the hypomorphic alleles reside on the hydrophobic face of a proposed amphipathic-helical region implicated biochemically in interacting with the t-SNAREs syntaxin and SNAP-25. Finally, we demonstrate that double mutants lacking both the v-SNAREs synaptotagmin and snb-1 are phenotypically similar to snb-1 mutants and less severe than syntaxin mutants. Our work demonstrates that synaptobrevin is essential for viability and is required for functional synaptic transmission. However, our analysis also suggests that transmitter release is not completely eliminated by removal of either one or both v-SNAREs.
突触小泡蛋白是与神经递质释放相关的囊泡蛋白，这一结论来自于生化研究以及使用肉毒杆菌毒素的干扰实验。为了在体内验证这些模型，我们分离并鉴定了后生动物中的首个突触小泡蛋白突变体，结果显示突变动物的神经传递受到严重破坏。缺乏snb-1的突变体在胚胎发育完成后随即死亡。这些濒死动物仍保留一些运动能力，尽管它们极度不协调且无法进食。我们还分离并鉴定了几个snb-1的亚等位基因突变体。尽管这些突变体完全存活，但它们表现出各种行为异常，这与突触传递效率的普遍缺陷一致。这些存活的突变体对乙酰胆碱酯酶抑制剂涕灭威具有抗性，表明胆碱能传递受损。对咽部肌肉的细胞外记录也显示突变体的突触传递存在严重缺陷。亚等位基因突变体中的分子损伤位于一个推测的两亲螺旋区域的疏水面上，该区域在生化上与t-SNARE蛋白 syntaxin和SNAP-25相互作用有关。最后，我们证明同时缺乏v-SNARE蛋白突触结合蛋白和snb-1的双突变体在表型上与snb-1突变体相似，但比syntaxin突变体的表型轻。我们的工作表明突触小泡蛋白对生存能力至关重要，并且是功能性突触传递所必需的。然而，我们的分析也表明，去除一个或两个v-SNARE蛋白并不会完全消除神经递质的释放。
