Lateral diffusion of inositol 1,4,5-trisphosphate receptor type 1 is regulated by actin filaments and 4.1N in neuronal Dendrites
Lateral diffusion of inositol 1,4,5-trisphosphate receptor type 1 is regulated by actin filaments and 4.1N in neuronal Dendrites
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DOI：
10.1074/jbc.m408364200
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发表时间：
2004-11-19
影响因子：
4.8
通讯作者：
Mikoshiba, K
中科院分区：
文献类型：
--
作者：
Fukatsu, K;Bannai, H;Mikoshiba, K
肌醇1，4，5-三磷酸受体1（Inositol 1，4，5-trisphosphate receptor type 1，IP（3）R1）在神经元功能中起重要作用，但其在内质网膜上的侧向扩散及其在活神经元中的调节作用尚不清楚。我们在培养的大鼠海马神经元中表达了绿色荧光蛋白标记的IP（3）R1，并通过光漂白后荧光恢复技术观察了其侧向扩散。IP（3）R1显示出横向扩散，有效扩散常数近似于0.3 mum（2）/s。肌动蛋白丝的消耗增加了IP（3）R1的扩散常数，表明IP（3）R1的扩散是通过肌动蛋白丝负调控的。我们还发现，与IP（3）R1结合并含有肌动蛋白-血影蛋白结合区的蛋白4.1N负责这种肌动蛋白对IP（3）R1扩散常数的调节。过表达显性负性4.1N和阻断4.1N与IP 3R 1的结合增加了IP（3）R1的扩散常数。IP（3）R3（IP（3）R3）是IP（3）Rs的一种亚型，缺乏与4.1N的结合能力，其扩散不依赖于肌动蛋白丝，但在加入4.1N结合序列后，其扩散依赖于肌动蛋白丝。这些数据表明，4.1N作为IP（3）R1和肌动蛋白丝之间的连接蛋白。这种依赖于肌动蛋白的IP（3）R1扩散调节可能对细胞内Ca 2+信号的时空调节很重要。
Inositol 1,4,5-trisphosphate receptor type1 (IP(3)R1) plays an important role in neuronal functions; however, the lateral diffusion of IP(3)R1 on the endoplasmic reticulum membrane and its regulation in the living neurons remain unknown. We expressed green fluorescent protein-tagged IP(3)R1 in cultured rat hippocampal neurons and observed the lateral diffusion by the fluorescence recovery after photobleaching technique. IP(3)R1 showed lateral diffusion with an effective diffusion constant of similar to 0.3 mum(2)/s. Depletion of actin filaments increased the diffusion constant of IP(3)R1, suggesting that the diffusion of IP(3)R1 is regulated negatively through actin filaments. We also found that protein 4.1N, which binds to IP(3)R1 and contains an actin-spectrin-binding region, was responsible for this actin regulation of the IP(3)R1 diffusion constant. Overexpression of dominant-negative 4.1N and blockade of 4.1N binding to IP3R1 increased the IP(3)R1 diffusion constant. The diffusion of IP3R type 3 (IP(3)R3), one of the isoforms of IP(3)Rs lacking the binding ability to 4.1N, was not dependent on actin filaments but became dependent on actin filaments after the addition of a 4.1N-binding sequence. These data suggest that 4.1N serves as a linker protein between IP(3)R1 and actin filaments. This actin filament-dependent regulation of IP(3)R1 diffusion may be important for the spatiotemporal regulation of intracellular Ca2+ signaling.