Gnanasambandam Radhakrishnan, Bae Chilman, Gottlieb Philip A, Sachs Frederick
State University of New York at Buffalo, Department of Physiology and Biophysics, Buffalo, New York, United States of America.
PLoS One. 2015 May 8;10(5):e0125503. doi: 10.1371/journal.pone.0125503. eCollection 2015.
Members of the eukaryotic PIEZO family (the human orthologs are noted hPIEZO1 and hPIEZO2) form cation-selective mechanically-gated channels. We characterized the selectivity of human PIEZO1 (hPIEZO1) for alkali ions: K+, Na+, Cs+ and Li+; organic cations: TMA and TEA, and divalents: Ba2+, Ca2+, Mg2+ and Mn2+. All monovalent ions permeated the channel. At a membrane potential of -100 mV, Cs+, Na+ and K+ had chord conductances in the range of 35-55 pS with the exception of Li+, which had a significantly lower conductance of ~ 23 pS. The divalents decreased the single-channel permeability of K+, presumably because the divalents permeated slowly and occupied the open channel for a significant fraction of the time. In cell-attached mode, 90 mM extracellular divalents had a conductance for inward currents carried by the divalents of: 25 pS for Ba2+ and 15 pS for Ca2+ at -80 mV and 10 pS for Mg2+ at -50 mV. The organic cations, TMA and TEA, permeated slowly and attenuated K+ currents much like the divalents. As expected, the channel K+ conductance increased with K+ concentration saturating at ~ 45 pS and the KD of K+ for the channel was 32 mM. Pure divalent ion currents were of lower amplitude than those with alkali ions and the channel opening rate was lower in the presence of divalents than in the presence of monovalents. Exposing cells to the actin disrupting reagent cytochalasin D increased the frequency of openings in cell-attached patches probably by reducing mechanoprotection.
真核生物PIEZO家族成员（人类直系同源物为hPIEZO1和hPIEZO2）形成阳离子选择性机械门控通道。我们对人类PIEZO1（hPIEZO1）对碱金属离子（K⁺、Na⁺、Cs⁺和Li⁺）、有机阳离子（TMA和TEA）以及二价离子（Ba²⁺、Ca²⁺、Mg²⁺和Mn²⁺）的选择性进行了表征。所有单价离子均可透过该通道。在膜电位为 -100 mV时，Cs⁺、Na⁺和K⁺的弦电导在35 - 55 pS范围内，Li⁺除外，其电导显著较低，约为23 pS。二价离子降低了K⁺的单通道通透性，可能是因为二价离子透过速度慢，且在相当一部分时间内占据开放通道。在细胞贴附模式下，90 mM细胞外二价离子在 -80 mV时对由二价离子携带的内向电流的电导为：Ba²⁺为25 pS，Ca²⁺为15 pS，在 -50 mV时Mg²⁺为10 pS。有机阳离子TMA和TEA透过缓慢，并且与二价离子一样，极大地减弱了K⁺电流。正如预期的那样，通道K⁺电导随K⁺浓度增加而增加，在约45 pS时达到饱和，通道对K⁺的解离常数（KD）为32 mM。纯二价离子电流的幅度低于单价离子电流，并且在存在二价离子时通道开放速率低于存在单价离子时。将细胞暴露于肌动蛋白破坏试剂细胞松弛素D可能通过减少机械保护作用增加了细胞贴附膜片的开放频率。
