A high affinity RIM-binding protein/Aplip1 interaction prevents the formation of ectopic axonal active zones.
A high affinity RIM-binding protein/Aplip1 interaction prevents the formation of ectopic axonal active zones.
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DOI：
10.7554/elife.06935
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发表时间：
2015-08-14
期刊：
影响因子：
7.7
通讯作者：
Sigrist SJ
中科院分区：
文献类型：
--
作者：
Siebert M;Böhme MA;Driller JH;Babikir H;Mampell MM;Rey U;Ramesh N;Matkovic T;Holton N;Reddy-Alla S;Göttfert F;Kamin D;Quentin C;Klinedinst S;Andlauer TF;Hell SW;Collins CA;Wahl MC;Loll B;Sigrist SJ
突触囊泡（SV）融合在由蛋白质支架覆盖的活性区（AZ），在果蝇突触由ELKS家族成员Bruchpilot（BRP）和RIM结合蛋白（RBP）组成。在这里，我们证明轴突共运输的BRP和RBP使用活体成像，这两种蛋白质共同积累在轴突聚集的几个运输突变体。RBP通过其C-末端Src-同源3（SH 3）结构域结合Aplip 1/JIP 1，Aplip 1/JIP 1是参与驱动蛋白依赖性SV转运的转运衔接子。我们显示在原子的细节，RBP C-末端SH 3域结合脯氨酸丰富（PxxP）基序的Aplip 1/JIP 1亚微摩尔亲和力。点突变这个PxxP基序引起异位AZ样结构在轴突膜的形成。AZ蛋白和转运衔接子之间的直接相互作用似乎提供了复杂的亲合力，并屏蔽了预组装支架蛋白转运复合物的突触相互作用表面，因此，有利于生理突触AZ组装超过轴突膜处的过早组装。http://dx.doi.org/10.7554/eLife.06935.001为了传递信息，组成神经系统的神经元在称为突触的结构上连接。被称为神经递质的化学信使从一个神经元释放出来，穿过突触引发邻近细胞的反应。新突触的形成在学习和记忆中起着重要作用，但这个过程的许多方面还没有得到很好的理解。在突触的一个特定区域称为活动区，蛋白质支架有助于释放神经递质。这些蛋白质在神经元的细胞体中产生，然后被运送到从细胞体伸出的细长轴突的末端。这对细胞提出了挑战，因为活性区支架的组分必须正确地靶向轴突末端的突触，确保活性区支架仅在其正确位置组装。Siebert，Böhme等人研究了果蝇活动区支架中发现的一些蛋白质如何沿沿着运输。用荧光标记物标记蛋白质，可以在显微镜下观察果蝇幼虫的运动。结果显示，两种蛋白质--BRP和RBP--是沿着轴突一起运输的。进一步的研究表明，这种运动需要一种名为Aplip 1的转运衔接蛋白，它与RBP结合。Siebert，Böhme等人建立了发生这种相互作用的RBP部分的结构，并发现突变该区域会导致神经元轴突部分的过早活性区支架组装。RBP和Aplip 1之间的相互作用非常强，这有助于防止支架在到达神经元的正确部分之前组装。一旦到达最终目的地（突触），转运适配器和活性区蛋白究竟是如何分离的还有待发现。DOI：http://dx.doi.org/10.7554/eLife.06935.002网站
Synaptic vesicles (SVs) fuse at active zones (AZs) covered by a protein scaffold, at Drosophila synapses comprised of ELKS family member Bruchpilot (BRP) and RIM-binding protein (RBP). We here demonstrate axonal co-transport of BRP and RBP using intravital live imaging, with both proteins co-accumulating in axonal aggregates of several transport mutants. RBP, via its C-terminal Src-homology 3 (SH3) domains, binds Aplip1/JIP1, a transport adaptor involved in kinesin-dependent SV transport. We show in atomic detail that RBP C-terminal SH3 domains bind a proline-rich (PxxP) motif of Aplip1/JIP1 with submicromolar affinity. Pointmutating this PxxP motif provoked formation of ectopic AZ-like structures at axonal membranes. Direct interactions between AZ proteins and transport adaptors seem to provide complex avidity and shield synaptic interaction surfaces of pre-assembled scaffold protein transport complexes, thus, favouring physiological synaptic AZ assembly over premature assembly at axonal membranes. DOI: http://dx.doi.org/10.7554/eLife.06935.001 To pass on information, the neurons that make up the nervous system connect at structures known as synapses. Chemical messengers called neurotransmitters are released from one neuron, and travel across the synapse to trigger a response in the neighbouring cell. The formation of new synapses plays an important role in learning and memory, but many aspects of this process are not well understood. In a specific region of the synapse called the active zone, a scaffold of proteins helps to release the neurotransmitters. These proteins are made in the cell body of the neuron, and are then transported to the end of the long, thin axons that protrude from the cell body. This presents a challenge for the cell, because the components of the active zone scaffold must be correctly targeted to the synapse at the end of the axon, ensuring the active zone scaffold assembles only at its proper location. Siebert, Böhme et al. studied how some of the proteins that are found in the active zone scaffold of the fruit fly Drosophila are transported along axons. Labelling the proteins with fluorescent markers allowed their movement to be examined under a microscope in living Drosophila larvae. The results showed that two of the proteins—known as BRP and RBP—are transported along the axons together. Further investigation revealed that a transport adaptor protein called Aplip1, which binds to RBP, is required for this movement. Siebert, Böhme et al. established the structure of the part of RBP where this interaction occurs, and found that mutating this region causes premature active zone scaffold assembly in the axonal part of the neuron. The interaction between RBP and Aplip1 is very strong, and this helps to prevent the scaffold assembling before it has reached the correct part of the neuron. Exactly how the transport adaptor and active zone protein are separated once they reach their final destination (the synapse) remains to be discovered. DOI: http://dx.doi.org/10.7554/eLife.06935.002