Germination of Nosema algerae (Microspora) spores: Conditional inhibition by D2O, ethanol and Hg2+ suggests dependence of water influx upon membrane hydration and specific transmembrane pathways
Germination of Nosema algerae (Microspora) spores: Conditional inhibition by D2O, ethanol and Hg2+ suggests dependence of water influx upon membrane hydration and specific transmembrane pathways
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DOI：
10.1111/j.1550-7408.1997.tb05946.x
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发表时间：
1997-03-01
影响因子：
2.2
通讯作者：
Undeen, AH
中科院分区：
文献类型：
--
作者：
Frixione, E;Ruiz, L;Undeen, AH
通过评估小孢子孢子对体外 Na+ 或 K+ 刺激的反应，研究了在预期影响水穿过质膜壁复合物的条件下小孢子孢子的萌发。用D2O部分或全部替代普通水，更有效地在离子和带静电的细胞表面涂覆相对稳定的水化层，以浓度依赖性方式延迟和抑制孢子萌发；然而，在 100% D2O 中预孵育并没有改变对标准刺激的正常反应。水结构破坏条件，例如温度升高（15°C 至 40°C 范围内）或离子强度升高（正常的 2 至 10 倍），会对抗 D2O 的抑制作用，并允许 Li+ 的显着刺激，Li+ 是具有最大水合直径的单价阳离子，对孢子的刺激作用通常较弱。已知乙醇可以减少水穿过细胞膜和磷脂双层的渗透，也会对孢子萌发产生强大的剂量依赖性（1% 至 4% v/v）抑制，但乙醇预处理不会影响正常反应。 HgCl2 是一种特定水通道的抑制剂，无论温度如何，在正常刺激溶液中，只要浓度为 250 μM，就能阻止孢子萌发，并且在高盐刺激溶液中仅允许延迟反应。然而，Hg2+ 的抑制作用因培养基中同时存在的 2-巯基乙醇而被消除。这些结果表明（1）孢子萌发强烈依赖于质膜壁复合物和刺激离子的水合状态，（2）渗透水通过具有关键巯基的特定跨膜途径流入孢子，即类似于促进水穿过高渗透性细胞质膜的水通道。
The germination of microsporidian spores under conditions expected to affect water how across the plasma membrane-wall complex was studied by assessing their responses to in vitro stimulation with Na+ or K+. Partial or full substitution of common water with D2O, which more effectively coats ions and electrostatically-charged cell surfaces with relatively stable hydration layers, delayed and inhibited spore germination in a concentration-dependent manner; yet, preincubation in 100% D2O did not change the normal response to standard stimulation. Water structure-breaking conditions, such as an increase in temperature (within the 15 degrees C to 40 degrees C range) or in ionic strength (2- to 10-fold normal), opposed the inhibition by D2O and allowed significant stimulation by Li+, the monovalent cation with the largest hydration diameter and a usually weak stimulant action on the spores. Ethanol, known to reduce water permeation across cell membranes and phospholipid bilayers, also caused a powerful and dose-dependent (1% to 4% v/v) inhibition of spore germination, but pretreatment with ethanol did not affect the normal response. HgCl2, an inhibitor of specific water channels, blocked spore germination at just 250 mu M in the normal stimulation solution irrespective of the temperature, and permitted only a delayed response in high salt stimulation solutions. However, the inhibition by Hg2+ was abolished by the simultaneous presence of 2-mercaptoethanol in the medium. These results suggest (1) that spore germination is keenly dependent upon the hydration states of both the plasma membrane-wall complex and the stimulant ions, and (2) that osmotic water flows into the spores through specific transmembrane pathways with critical sulfhydryl groups, i.e. analogous to the water channels that facilitate water movements across the plasma membranes of highly permeable cells.