Adaptive behavior of bacterial mechanosensitive channels is coupled to membrane mechanics.
Adaptive behavior of bacterial mechanosensitive channels is coupled to membrane mechanics.
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DOI：
10.1085/jgp.200910371
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发表时间：
2010-06
期刊：
影响因子：
--
通讯作者：
Sukharev S
中科院分区：
文献类型：
--
作者：
Belyy V;Kamaraju K;Akitake B;Anishkin A;Sukharev S
小电导机械敏感通道(MSCS)是一种位于大肠杆菌内膜上的张力驱动渗透压释放阀，它表现出复杂的适应性行为，而其功能对应的大电导机械敏感通道(MSCL)通常被认为是非适应性的。在这项研究中，我们表明，这两个通道在切除的斑块中表现出类似的适应，这一过程完全可以与仅在MSCs中突出的失活分开。当膜片在恒定压力下保持时，两个通道的适应表现为可逆的电流下降。用1-10-S的压力斜率记录的剂量-效应曲线相对于用一系列脉冲测量的曲线向更高的张力方向移动，表明张力敏感性降低。切除的贴片长期暴露在阈值以下的张力下，MSCs和MSCL的激活曲线进一步向更高的张力移动，具有相似的幅度和时间进程。全球体MSCs的同步成像记录显示，激活曲线的中点张力为7.8mN/m，斜率对应于∼15nm2的平面内扩张。在整个球体模式下保持失活，但没有观察到适应。同样，MSCL(V23T突变体)的整个球体记录表明没有适应，这在切除的斑块中存在。在球体贴壁模式下，MSCs活性在球体完好时没有表现出适应，但通透性的球体表现出延迟适应，提示膜断裂或边缘的存在导致了适应。我们在双层耦合的机制框架下解释了这一点，将切除斑块中通道的适应与未与玻璃吸管接触的内部小叶的松弛联系起来。一个小叶的松弛导致双层中张力的不对称重分布，这不利于通道的打开。
Mechanosensitive channel of small conductance (MscS), a tension-driven osmolyte release valve residing in the inner membrane of Escherichia coli, exhibits a complex adaptive behavior, whereas its functional counterpart, mechanosensitive channel of large conductance (MscL), was generally considered nonadaptive. In this study, we show that both channels exhibit similar adaptation in excised patches, a process that is completely separable from inactivation prominent only in MscS. When a membrane patch is held under constant pressure, adaptation of both channels is manifested as a reversible current decline. Their dose–response curves recorded with 1–10-s ramps of pressure are shifted toward higher tension relative to the curves measured with series of pulses, indicating decreased tension sensitivity. Prolonged exposure of excised patches to subthreshold tensions further shifts activation curves for both MscS and MscL toward higher tension with similar magnitude and time course. Whole spheroplast MscS recordings performed with simultaneous imaging reveal activation curves with a midpoint tension of 7.8 mN/m and the slope corresponding to ∼15-nm2 in-plane expansion. Inactivation was retained in whole spheroplast mode, but no adaptation was observed. Similarly, whole spheroplast recordings of MscL (V23T mutant) indicated no adaptation, which was present in excised patches. MscS activities tried in spheroplast-attached mode showed no adaptation when the spheroplasts were intact, but permeabilized spheroplasts showed delayed adaptation, suggesting that the presence of membrane breaks or edges causes adaptation. We interpret this in the framework of the mechanics of the bilayer couple linking adaptation of channels in excised patches to the relaxation of the inner leaflet that is not in contact with the glass pipette. Relaxation of one leaflet results in asymmetric redistribution of tension in the bilayer that is less favorable for channel opening.
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影响因子：
2.9
作者：
Kamaraju, Kishore;Sukharev, Sergei
通讯作者：
Sukharev, Sergei
影响因子：
11.4
作者：
Li, YZ;Moe, PC;Blount, P
通讯作者：
Blount, P
影响因子：
1.1
作者：
Baoukina, SV;Mukhin, SI
通讯作者：
Mukhin, SI
DOI：
10.1085/jgp.200409198
发表时间：
2005-02
期刊：
The Journal of general physiology
影响因子：
--
作者：
Akitake B;Anishkin A;Sukharev S
通讯作者：
Sukharev S
影响因子：
5.5
作者：
Suchyna, Thomas M.;Sachs, Frederick
通讯作者：
Sachs, Frederick