Regulation of the epithelial Na+ channel by membrane tension.
Regulation of the epithelial Na+ channel by membrane tension.
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DOI：
10.1085/jgp.112.2.97
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发表时间：
1998-08
期刊：
影响因子：
--
通讯作者：
Subramanyam M
中科院分区：
文献类型：
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作者：
Awayda MS;Subramanyam M
在非洲爪哇卵母细胞表达系统中，采用双电极电压钳和细胞附着式膜片钳方法，研究了αβγ大鼠上皮钠通道(RENaC)对渗透压和机械刺激引起的膜张力变化的敏感性。ENAC全细胞电流对直接注入90或180nL 100 mM KCl引起的机械性细胞肿胀不敏感。同样，ENaC全细胞电流对由33%的洗浴溶液渗透压降低引起的渗透细胞肿胀不敏感。细胞肿胀对ENaC的影响与肌动蛋白细胞骨架的状态无关，因为ENaC对细胞松弛素B处理2-5h的渗透和机械细胞肿胀不敏感，这种ENaC对细胞体积增加和膜张力变化的明显不敏感也在单通道水平上观察到，在5英寸或10英寸的正负压力下也可以观察到。一桶水。然而，与缺乏细胞膨胀效应相反，ENaC电流被细胞收缩所抑制。在260momol溶液中孵育45min(溶液渗透压增加25%)，使ENaC电流(−100 mV)从−3.42±0.34降至−2.02±0.23μA(n=6)。用细胞松弛素B处理卵母细胞可完全阻断这种电流随细胞收缩而降低的趋势，表明电流的这种变化不太可能与细胞收缩的直接作用有关。我们得出结论，当αβγrENaC在一个系统中表达时，它不是直接机械敏感的，该系统可以产生与天然上皮中发现的相同性质的通道。
The sensitivity of αβγ rat epithelial Na+ channel (rENaC) to osmotically or mechanically induced changes of membrane tension was investigated in the Xenopus oocyte expression system, using both dual electrode voltage clamp and cell-attached patch clamp methodologies. ENaC whole-cell currents were insensitive to mechanical cell swelling caused by direct injection of 90 or 180 nl of 100-mM KCl. Similarly, ENaC whole-cell currents were insensitive to osmotic cell swelling caused by a 33% decrease of bathing solution osmolarity. The lack of an effect of cell swelling on ENaC was independent of the status of the actin cytoskeleton, as ENaC remained insensitive to osmotic and mechanical cell swelling in oocytes pretreated with cytochalasin B for 2–5 h. This apparent insensitivity of ENaC to increased cell volume and changes of membrane tension was also observed at the single channel level in membrane patches subjected to negative or positive pressures of 5 or 10 in. of water. However, and contrary to the lack of an effect of cell swelling, ENaC currents were inhibited by cell shrinking. A 45-min incubation in a 260-mosmol solution (a 25% increase of solution osmolarity) caused a decrease of ENaC currents (at −100 mV) from −3.42 ± 0.34 to −2.02 ± 0.23 μA (n = 6). This decrease of current with cell shrinking was completely blocked by pretreatment of oocytes with cytochalasin B, indicating that these changes of current are not likely related to a direct effect of cell shrinking. We conclude that αβγ rENaC is not directly mechanosensitive when expressed in a system that can produce a channel with identical properties to those found in native epithelia.