Expression of Rem2, an RGK family small GTPase, reduces N-type calcium current without affecting channel surface density
Expression of Rem2, an RGK family small GTPase, reduces N-type calcium current without affecting channel surface density
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DOI：
10.1523/jneurosci.3111-05.2005
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发表时间：
2005-10-19
影响因子：
5.3
通讯作者：
Ikeda, SR
中科院分区：
文献类型：
--
作者：
Chen, HM;Puhl, HL;Ikeda, SR
Rad、Gem/Kir、Rem 和 Rem2 是小 GTP 结合蛋白 Ras 相关 RGK（Rad、Gem 和 Kir）家族的成员。 RGK 蛋白的异源表达会干扰钙通道从头组装/运输，并显着降低先前存在的高压激活钙通道产生的电流幅度。这些效应可能是由于 RGK 蛋白与钙通道 β 亚基的直接相互作用所致。在RGK家族中，Rem2是唯一在神经元组织中大量表达的成员。在这里，我们检查了 Rem2 调节大鼠交感神经节和背根神经节神经元内源性电压激活钙通道的能力。 Rem2的异源表达几乎消除了先前存在的高电压激活的钙通道产生的钙电流，而不影响低电压激活的钙通道。 Rem2 对 N 型钙通道的抑制需要 Ras 同源（核心）结构域和多元 C 末端。 Rem2 中假定的 GTP/Mg2+ 结合基序的突变不会影响钙电流的抑制。通过贴片移液器向神经元加载 GDP-β-S 并不能逆转 Rem2 介导的钙通道抑制。最后，在钙电流完全消除时，稳定表达N-型钙通道的tsA201细胞中的[I-125]Tyr(22)-omega-芋螺毒素GVIA细胞表面结合不因Rem2表达而改变。总之，我们的结果支持了一个模型，其中 Rem2 通过 C 末端多元基序定位于质膜，并与预组装的 N 型通道中的钙通道 β 亚基相互作用，从而形成非导电物质。
Rad, Gem/Kir, Rem, and Rem2 are members of the Ras-related RGK (Rad, Gem, and Kir) family of small GTP-binding proteins. Heterologous expression of RGK proteins interferes with de novo calcium channel assembly/trafficking and dramatically decreases the amplitude of currents arising from preexisting high-voltage-activated calcium channels. These effects probably result from the direct interaction of RGK proteins with calcium channel beta subunits. Among the RGK family, Rem2 is the only member abundantly expressed in neuronal tissues. Here, we examined the ability of Rem2 to modulate endogenous voltage-activated calcium channels in rat sympathetic and dorsal root ganglion neurons. Heterologous expression of Rem2 nearly abolished calcium currents arising from preexisting high-voltage-activated calcium channels without affecting low-voltage-activated calcium channels. Rem2 inhibition of N-type calcium channels required both the Ras homology (core) domain and the polybasic C terminus. Mutation of a putative GTP/Mg2+ binding motif in Rem2 did not affect suppression of calcium currents. Loading neurons with GDP-beta-S via the patch pipette did not reverse Rem2mediated calcium channel inhibition. Finally, [I-125] Tyr(22)-omega-conotoxin GVIA cell surface binding in tsA201 cells stably expressing N- type calcium channels was not altered by Rem2 expression at a time when calcium current was totally abolished. Together, our results support a model in which Rem2 localizes to the plasma membrane via a C- erminal polybasic motif and interacts with calcium channel beta subunits in the preassembled N- type channel, thereby forming a nonconducting species.