The carboxyl terminal domain regulates the unitary conductance and voltage dependence of connexin40 gap junction channels
The carboxyl terminal domain regulates the unitary conductance and voltage dependence of connexin40 gap junction channels
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DOI：
10.1161/hh0701.088833
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发表时间：
2001-04-13
影响因子：
20.1
通讯作者：
Delmar, M
中科院分区：
文献类型：
--
作者：
Anumonwo, JMB;Taffet, SM;Delmar, M
连接蛋白（Cx） 40和Cx43的化学调控遵循一个球链模型，其中羧基末端（CT）结构域作为一个门控颗粒，与附属于孔的受体结合。此外，Cx40通道可以通过与Cx43的CT域的异域相互作用而关闭，反之亦然。在这里，我们报道了在N2A细胞中建立Cx40的统一电导和电压依赖谱的类似相互作用。野生型Cx40检测到两个平均单位电导值（“低电导”和“主”）。氨基酸248 (Cx40tr248) CT结构域的截断导致低电导态的消失。Cx40tr248与Cx40（同域相互作用）或Cx43（异域相互作用）的CT片段共表达，挽救了Cx40的单一电导谱。在N2A细胞中，野生型Cx40通道宏观结电流弛豫的时间过程最好用双指数函数来描述，但截断后变为单指数函数。然而。在卵母细胞表达系统中记录的宏观连接电流在野生型和突变型通道之间没有显著差异。Cx43的CT结构域与Cx40的1 ~ 248个氨基酸的连接产生了一个具有统一电导和电压门控曲线的嵌合通道，与野生型Cx40没有区别。我们得出结论，Cx40通道在低电导状态下的驻留涉及CT域和孔隙形成区域之间的球-链型相互作用。这种相互作用可以是同源的（Cx40截断与Cx40CT）或异源的（与Cx43CT）。
Chemical regulation of connexin (Cx) 40 and Cx43 follows a ball-and-chain model, in which the carboxyl terminal (CT) domain acts as a gating particle that binds to a receptor affiliated with the pore. Moreover, Cx40 channels can be closed by a heterodomain interaction with the CT domain of Cx43 and vice versa, Here, we report similar interactions in the establishment of the unitary conductance and voltage-dependent profile of Cx40 in N2A cells. Two mean unitary conductance values ("lower conductance" and ''main") were detected in wild-type Cx40. Truncation of the CT domain at amino acid 248 (Cx40tr248) caused the disappearance of the lower-conductance state. Coexpression of Cx40tr248 with the CT fragment of either Cx40 (homodomain interactions) or Cx43 (heterodomain interactions) rescued the unitary conductance profile of Cx40. In the N2A cells, the time course of macroscopic junctional current relaxation was best described by a biexponential function in the wild-type Cx40 channels, but it was reduced to a single-exponential function after truncation. However. macroscopic junctional currents recorded in the oocyte expression system were not significantly different between the wild-type and mutant channels. Concatenation of the CT domain of Cx43 to amino acids 1 to 248 of Cx40 yielded a chimeric channel with unitary conductance and voltage-gating profile indistinguishable from that of wild-type Cx40. We conclude that residence of Cx40 channels in the lower-conductance state involves a ball-and-chain type of interaction between the CT domain and the pore-forming region. This interaction can be either homologous (Cx40 truncation with Cx40CT) or heterologous (with the Cx43CT).