Mutations in a drosophila α2δ voltage-gated calcium channel subunit reveal a crucial synaptic function
Mutations in a drosophila α2δ voltage-gated calcium channel subunit reveal a crucial synaptic function
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DOI：
10.1523/jneurosci.4498-07.2008
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发表时间：
2008-01-02
影响因子：
5.3
通讯作者：
Schwarz, Thomas L.
中科院分区：
文献类型：
--
作者：
Dickman, Dion K.;Kurshan, Peri T.;Schwarz, Thomas L.
电压依赖性钙通道调节神经元生物学的许多方面，包括突触传递。除了编码基本电压门和选择性孔的α(1)亚基外，钙通道还包含辅助的α (2) δ、β和γ亚基。尽管在了解钙通道的生物物理特性方面取得了进展，但这些辅助亚基的体内功能仍不清楚。我们在果蝇中使用正向遗传筛选分离了编码α (2) δ钙通道亚基（d α (2) δ -3）的基因突变。该基因的零突变是胚胎致死性的，可以通过在神经系统中的表达来拯救，这表明该亚基的基本功能是神经元的。d α (2) δ -3突变体的光感受器表型与钙通道α(1)突变体的不和谐（cac）相似，表明它们具有共同的功能。我们已经详细研究了存活到第三阶段的基因型。电生理记录表明，这些突变体的突触传递严重受损。因此，α (2) δ钙通道亚基对钙依赖性突触功能至关重要。因此，这个果蝇亚型可能是由cac位点编码的突触前钙通道α(1)亚基的伴侣。与这一假设相一致，d α (2) δ -3突变体中神经肌肉连接处的cacGFP荧光减少。这是在任何生物体中首次表征α (2) δ -3突变体，并表明α (2) δ -3在突触前囊泡释放和活跃区钙通道表达中发挥必要作用。
Voltage-dependent calcium channels regulate many aspects of neuronal biology, including synaptic transmission. In addition to their alpha(1) subunit, which encodes the essential voltage gate and selective pore, calcium channels also contain auxiliary alpha(2)delta, beta, and gamma subunits. Despite progress in understanding the biophysical properties of calcium channels, the in vivo functions of these auxiliary subunits remain unclear. We have isolated mutations in the gene encoding an alpha(2)delta calcium channel subunit (d alpha(2)delta-3) using a forward genetic screen in Drosophila. Null mutations in this gene are embryonic lethal and can be rescued by expression in the nervous system, demonstrating that the essential function of this subunit is neuronal. The photoreceptor phenotype of d alpha(2)delta-3 mutants resembles that of the calcium channel alpha(1) mutant cacophony (cac), suggesting shared functions. We have examined in detail genotypes that survive to the third-instar stage. Electrophysiological recordings demonstrate that synaptic transmission is severely impaired in these mutants. Thus the alpha(2)delta calcium channel subunit is critical for calcium-dependent synaptic function. As such, this Drosophila isoform is the likely partner to the presynaptic calcium channel alpha(1) subunit encoded by the cac locus. Consistent with this hypothesis, cacGFP fluorescence at the neuromuscular junction is reduced in d alpha(2)delta-3 mutants. This is the first characterization of an alpha(2)delta-3 mutant in any organism and indicates a necessary role for alpha(2)delta-3 in presynaptic vesicle release and calcium channel expression at active zones.