Opposing modulation of Cx26 gap junctions and hemichannels by CO2.
Opposing modulation of Cx26 gap junctions and hemichannels by CO2.
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CO2 对 Cx26 间隙连接和半通道的反向调节。
DOI：
10.1113/jp280747
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Nijjar S
中科院分区：
文献类型：
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作者：
Nijjar S
关键点适度增加（55 mmHg）关闭Cx 26间隙连接。CO2的这种作用不受细胞内或细胞外pH值变化的影响。CO2依赖性关闭作用取决于相同的残基（K125和R104）Cx 26的病理性突变使差距连接的CO2依赖性关闭消失。弹性网络模型表明，CO2对Cx 26半通道和缝隙连接的影响是通过蛋白质最低熵状态的变化介导的。在这里，我们调查的行动CO2对Cx 26缝隙连接。使用染料转移试验，我们发现，55毫米汞柱的升高大大延迟了由Cx 26间隙连接耦合的HeLa细胞之间的荧光葡萄糖类似物（NBDG）的渗透。然而，突变K125 R或R104 A消除了CO2的这种作用。全细胞记录显示，CO2升高降低了Cx 26间隙连接电导（中位数降低66.7%，95%CI，50.5-100.0%），但对Cx 26 K125 R或Cx 31间隙连接无影响。CO2可引起细胞内酸化。使用30 mm丙酸盐，我们发现在没有变化的情况下酸化导致间隙差距结电导中值降低41.7%（95% CI，26.6-53.7%）。丙酸盐的这种作用不受K125 R突变的影响（中位数降低48.1%，95% CI，28.0-86.3%）。因此，差距连接的pH依赖性和CO2依赖性闭合在机制上是独立的。与角膜炎鱼鳞病耳聋综合征相关的Cx 26突变（N14 K、A40 V和A88 V）与突变M151 L组合，也消除了CO2依赖性间隙连接闭合。弹性网络模型表明，当CO2被束缚时，最低熵状态是差距连接的闭合构型，而半通道的开放状态。因此，CO2对Cx 26间隙连接和半通道的相反作用取决于相同的残基和假定的氨甲酰化反应。
Key pointsA moderate increase in (55 mmHg) closes Cx26 gap junctions.This effect of CO2is independent of changes in intra‐ or extracellular pH.The CO2‐dependent closing effect depends on the same residues (K125 and R104) that are required for the CO2‐dependent opening of Cx26 hemichannels.Pathological mutations of Cx26 abolish the CO2‐dependent closing of the gap junction.Elastic network modelling suggests that the effect of CO2on Cx26 hemichannels and gap junctions is mediated through changes in the lowest entropy state of the protein.AbstractCx26 hemichannels open in response to moderate elevations of CO2( 55 mmHg) via a carbamylation reaction that depends on residues K125 and R104. Here we investigate the action of CO2on Cx26 gap junctions. Using a dye transfer assay, we found that an elevated of 55 mmHg greatly delayed the permeation of a fluorescent glucose analogue (NBDG) between HeLa cells coupled by Cx26 gap junctions. However, the mutations K125R or R104A abolished this effect of CO2. Whole cell recordings demonstrated that elevated CO2reduced the Cx26 gap junction conductance (median reduction 66.7%, 95% CI, 50.5–100.0%) but had no effect on Cx26K125Ror Cx31 gap junctions. CO2can cause intracellular acidification. Using 30 mmpropionate, we found that acidification in the absence of a change in caused a median reduction in the gap junction conductance of 41.7% (95% CI, 26.6–53.7%). This effect of propionate was unaffected by the K125R mutation (median reduction 48.1%, 95% CI, 28.0–86.3%). pH‐dependent and CO2‐dependent closure of the gap junction are thus mechanistically independent. Mutations of Cx26 associated with the keratitis ichthyosis deafness syndrome (N14K, A40V and A88V), in combination with the mutation M151L, also abolished the CO2‐dependent gap junction closure. Elastic network modelling suggests that the lowest entropy state when CO2is bound is the closed configuration for the gap junction but the open state for the hemichannel. The opposing actions of CO2on Cx26 gap junctions and hemichannels thus depend on the same residues and presumed carbamylation reaction.