Different domains of the AMPA receptor direct stargazin-mediated trafficking and stargazin-mediated modulation of kinetics
Different domains of the AMPA receptor direct stargazin-mediated trafficking and stargazin-mediated modulation of kinetics
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DOI：
10.1074/jbc.m600679200
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发表时间：
2006-08-18
影响因子：
4.8
通讯作者：
Partin, Kathryn M.
中科院分区：
文献类型：
--
作者：
Bedoukian, Matthew A.;Weeks, Autumn M.;Partin, Kathryn M.
Stargazin是AMPA受体的一种辅助蛋白，可以增强AMPA受体的表面表达并影响其生物物理特性。这两种过程所必需的AMPA受体结构域尚未确定。在这里，我们使用共聚焦成像和电生理研究异源表达、荧光团标记的GluR1、GluR2和stargazin的表面表达和脱敏动力学。stargazin介导的转运对AMPA受体胞质结构域的性质很敏感。在GluR1i截断的细胞质尾部残基15后插入YFP会干扰星参素介导的受体运输，但不会干扰其对脱敏动力学的调节。这种结构也不允许荧光共振能量转移（FRET）与星gazin在内质网（ER）中，而荧光团标记的星gazin和未截断的AMPA受体之间的FRET表明，内质网和质膜中这些蛋白质之间存在特异性相互作用。而不是编码一个特定的结合位点，荧光团标记的C末端可能限制进入一个或多个内质网保留位点。尽管对C端的扰动阻碍了星甲苷介导的转运到质膜，但星甲苷对AMPA受体生物物理特性的影响（即脱敏的调节）仍然是完整的。这些数据提供了强有力的证据，表明星形蛋白调节门控和运输所需的AMPA受体结构域是可分离的。
Stargazin is an accessory protein of AMPA receptors that enhances surface expression and also affects the biophysical properties of the receptor. AMPA receptor domains necessary for either of these two processes have not yet been identified. Here, we used confocal imaging and electrophysiology of heterologously expressed, fluorophore-tagged GluR1, GluR2, and stargazin to study surface expression and desensitization kinetics. Stargazin-mediated trafficking was sensitive to the nature of the AMPA receptor cytoplasmic domain. The insertion of YFP after residue 15 of the truncated cytoplasmic tail of GluR1i perturbed stargazin-mediated trafficking of the receptor but not its modulation of desensitization kinetics. This construct also failed to permit fluorescence resonance energy transfer ( FRET) with stargazin in the endoplasmic reticulum ( ER), whereas FRET between fluorophore-tagged stargazin and non-truncated AMPA receptors demonstrated a specific interaction between these proteins, both in the ER and the plasma membrane. Rather than encoding a specific binding site, the fluorophore-tagged C terminus may restrict access to one or more ER retention sites. Although perturbations of the C terminus impeded stargazin-mediated trafficking to the plasma membrane, the effects of stargazin on the biophysical properties of AMPA receptors ( i.e. modulation of desensitization) remained intact. These data provide strong evidence that the AMPA receptor domains required for stargazin modulation of gating and trafficking are separable.