Jiang C, Haddad G G
Department of Pediatrics (Section of Respiratory Medicine), Yale University School of Medicine, New Haven, CT 06520.
Proc Natl Acad Sci U S A. 1994 Jul 19;91(15):7198-201. doi: 10.1073/pnas.91.15.7198.
The cascade of cellular events that is triggered by low O2 levels in the central nervous system depends on initial sensing mechanisms that can be crucial in determining the overall cell response, adaptation, or injury. In this report, we demonstrate that the activity of an identified K+ channel is regulated directly by environmental O2. Membrane ionic currents were recorded from neurons of the neocortex and the substantia nigra and studied by using whole-cell or excised membrane patches. O2 deprivation reversibly induced an initial transient increase in whole-cell outward currents, and this was followed by a pronounced decrease in these currents. In cell-free excised membrane patches, lack of O2 reversibly inhibited a class of K+ channels that are inhibited by ATP and activated by Ca2+. K+ channel inhibition depended on pO2 level, with a 50% inhibition at approximately 11 torr (1 torr = 6.9 kPa). By the use of specific agents that chelate metal in metal-containing O2-sensing centers, including heme, nonheme iron, copper, and flavin, we also demonstrated that iron-center but not copper-center blockers inhibited the channel in excised patches in a similar fashion as low pO2. These results strongly suggest that K+ channel activity is modulated during O2 deprivation by nonheme iron-containing proteins that are associated with channel molecules, thus providing evidence for a direct O2-sensing mechanism in neuronal membranes.
中枢神经系统中低氧水平引发的一系列细胞事件取决于初始传感机制，这些机制在决定细胞的整体反应、适应或损伤方面可能至关重要。在本报告中，我们证明了一种已确定的钾离子通道的活性直接受环境氧气的调节。我们从新皮层和黑质的神经元记录膜离子电流，并使用全细胞或膜片钳技术进行研究。缺氧可逆地诱导全细胞外向电流最初短暂增加，随后这些电流显著降低。在无细胞的膜片钳记录中，缺氧可逆地抑制一类受三磷酸腺苷（ATP）抑制并被钙离子（Ca2+）激活的钾离子通道。钾离子通道抑制取决于氧分压水平，在约11托（1托 = 6.9千帕）时抑制率达50%。通过使用能螯合含金属的氧气传感中心（包括血红素、非血红素铁、铜和黄素）中的金属的特定试剂，我们还证明，铁中心阻滞剂而非铜中心阻滞剂在膜片钳记录中以与低氧分压类似的方式抑制该通道。这些结果有力地表明，在缺氧期间，钾离子通道活性受与通道分子相关的含非血红素铁的蛋白质调节，从而为神经元膜中的直接氧气传感机制提供了证据。
