Properties of mouse connexin 30.2 and human connexin 31.9 hemichannels: Implications for atrioventricular conduction in the heart
Properties of mouse connexin 30.2 and human connexin 31.9 hemichannels: Implications for atrioventricular conduction in the heart
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DOI：
10.1073/pnas.0603372103
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发表时间：
2006-06-20
影响因子：
11.1
通讯作者：
Willecke, Klaus
中科院分区：
文献类型：
--
作者：
Bukauskas, Feliksas F.;Kreuzberg, Maria M.;Willecke, Klaus
四种连接蛋白（Cx），小鼠（m）Cx 30.2、Cx 40、Cx 43和Cx 45，决定小鼠心脏中的细胞-细胞电信号，并且已知Cx 43和Cx 45形成非并置半通道。在这里，我们表明，mCx30.2，这是最丰富的表达在心脏的窦房和房室结区域，其推定的人类直系同源物，人类（h）Cx31.9，也形成功能性半通道，这是像mCx30.2细胞-细胞通道，可渗透的阳离子染料高达约400 Da的大小。表达mCx30.2的HeLa细胞的DAPI摄取比HeLa亲本细胞快> 10倍。在无Ca ~（2+）的培养基中，HeLaCx30.2EGFP细胞对DAPI的摄取增加了约2倍，但亲本细胞的摄取不受影响。相反，通过施加CO2的酸化降低了HeLaCx30.2-EGFP细胞对DAPI的摄取，但对亲本细胞的摄取几乎没有影响。表达mCx30.2的细胞表现出比表达任何其他心脏Cx的细胞更高的DAPI摄取速率。转染hCx31.9-EGFP的2日龄大鼠心肌细胞摄取DAPI和溴化乙锭的速度比野生型心肌细胞快5-10倍。甲氟喹，奎宁和奎尼丁，表现出抗疟疾和antiembryonic特性，减少细胞-细胞连接的电导和染料摄取通过mCx 30.2半通道具有大致相同的亲和力（IC 50 =约10 μ M）和增加的依赖性的连接电导的跨接电压。mCx 30.2半通道的单位电导接近20 pS，约为细胞-细胞通道电导的两倍。mCx30.2和hCx31.9形成的半通道可能通过缩短空间常数和使可兴奋膜去极化来减缓窦房结和房室结中兴奋的传播。
Four connexins (Cxs), mouse (m)Cx30.2, Cx40, Cx43, and Cx45, determine cell-cell electrical signaling in mouse heart, and Cx43 and Cx45 are known to form unapposed hemichannels. Here we show that mCx30.2, which is most abundantly expressed in sinoatrial and atrioventricular nodal regions of the heart, and its putative human ortholog, human (h)Cx31.9, also form functional hemichannels, which, like mCx30.2 cell-cell channels, are permeable to cationic dyes up to approximate to 400 Da in size. DAPI uptake by HeLa cells expressing mCx30.2 was > 10-fold faster than that by HeLa parental cells. In Ca2+-free medium, uptake of DAPI by HeLaCx30.2EGFP cells was increased approximate to 2-fold, but uptake by parental cells was not affected. Conversely, acidification by application of CO2 reduced DAPI uptake by HeLaCx30.2-EGFP cells but had little effect on uptake by parental cells. Cells expressing mCx30.2 exhibited higher rates of DAPI uptake than did cells expressing any of the other cardiac Cxs. Cardiomyocytes of 2-day-old rats transfected with hCx31.9-EGFP took up DAPI and ethidium bromide 5-10 times faster than wild-type cardiomyocytes. Mefloquine, a close derivative of quinine and quinidine that exhibits antimalarial and antiarrhythmic properties, reduced conductance of cell-cell junctions and dye uptake through mCx30.2 hemichannels with approximately the same affinity (IC50 = approximate to 10 mu M) and increased dependence of junctional conductance on transjunctional voltage. Unitary conductance of mCx30.2 hemichannels was approximate to 20 pS, about twice the cell-cell channel conductance. Hemichannels formed of mCx30.2 and hCx31.9 may slow propagation of excitation in the sinoatrial and atrioventricular nodes by shortening the space constant and depolarizing the excitable membrane.