Species specificity of mammalian connexin-26 to form open voltage-gated hemichannels
Species specificity of mammalian connexin-26 to form open voltage-gated hemichannels
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DOI：
10.1096/fj.06-5828com
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发表时间：
2006-11-01
期刊：
影响因子：
4.8
通讯作者：
Barrio, Luis C.
中科院分区：
文献类型：
--
作者：
Gonzalez, Daniel;Gomez-Hernandez, Juan M.;Barrio, Luis C.
连接蛋白-26(Cx26)的突变会导致非综合征性听力损失和其他影响外胚层组织的综合征。虽然这些疾病的确切机制仍不清楚，但Cx通常被认为通过形成缝隙连接通道来调节细胞间的通讯。我们在这里表明，与大鼠Cx26不同，人和羊的Cx26在卵母细胞和Neuro2A细胞中表达时形成电压门控半通道。啮齿动物蛋白第159位的单一进化氨基酸变化，即人和绵羊蛋白中天冬氨酸被天冬氨酸取代，解释了这种物种特异性。在静息电位和正常的毫米级细胞外钙离子中，开放的人Cx26半通道可以通过电生理学和染料摄取检测到，尽管它们不影响细胞活力。这些半通道以接近-50 mV的速度开放，它们的激活随着去极化而增加，直到它们在正膜电位时失活。单通道分析表明，激活和失活涉及两种不同的电压门控机制，完全开放的半通道的电导是细胞间通道的两倍。半通道的存在在膜电位的生理控制下开放，这可能对人类Cx26的正常和病理活动有重要意义，特别是关于听力和表皮。
Mutations of connexin-26 (Cx26) cause nonsyndromic hearing loss and other syndromes affecting ectoderm-derived tissues. While the exact mechanisms underlying these diseases remain elusive, Cx's are generally considered to mediate cell-to-cell communication by forming gap junction channels. We show here that unlike rat Cx26, human and sheep Cx26 form voltage-gated hemichannels when expressed in oocytes and Neuro2A cells. A single evolutionary amino acidic change at position 159 of the rodent protein, the replacement of aspartic acid with asparagine in the human and sheep proteins, accounts for this species specificity. At the resting potential and in normal millimolar extracellular calcium, open human Cx26 hemichannels can be detected both electrophysiologically and by dye uptake, although they did not affect cell viability. These hemichannels opened at similar to - 50 mV and their activation increased by depolarization until they inactivate at positive membrane potentials. Single-channel analysis revealed that activation and inactivation involved two distinct voltage gating mechanisms and that the fully open hemichannel displays a conductance twice that of the intercellular channel. The existence of a hemichannel that opens under physiological control of the membrane potential may have important implications for the normal and pathological activity of Cx26 in humans, particularly with respect to hearing and the epidermis.