Acclimation of sperm motility apparatus in seawater-acclimated euryhaline tilapia Oreochromis mossambicus
Acclimation of sperm motility apparatus in seawater-acclimated euryhaline tilapia Oreochromis mossambicus
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DOI：
10.1242/jeb.00748
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发表时间：
2004-01-01
影响因子：
2.8
通讯作者：
Okuno, M
中科院分区：
文献类型：
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作者：
Morita, M;Takemura, A;Okuno, M
广盐罗非鱼Oreochromis mossambicus可以在淡水和海水中繁殖。精子活力的调节似乎在鱼类从淡水到海水的适应过程中受到调节，与淡水中的细胞外 Ca2+ 无关，而依赖于海水中的细胞外 Ca2+。在细胞外Ca2+存在的情况下，海水适应的罗非鱼(SWT)的精子即使在高渗环境下也表现出运动性，而淡水适应的罗非鱼(FWT)的精子则不具有运动性。 Ca2+ 指示剂 Fluo-3 显示，SWT 精子的细胞内 Ca2+ 浓度 [Ca2+]i 仅在低渗或高渗条件下存在细胞外 Ca2+ 时才会增加。由于 FWT 精子中 [Ca2+]i 的增加是在低渗条件下通过细胞内 Ca2+ 储存发生的，因此罗非鱼可能将 [Ca2+]i 增加的来源从细胞内储存（在 FWT 精子中）调节到细胞外储存（在 SWT 精子中）。使用脱膜精子的实验表明，Ca2+ 对于激活活力是必需的，这表明 Ca2+ 在 SWT 精子的运动调节中起着关键作用。我们检测到三种与精子活力激活相关的磷蛋白。 15 kDa 和 18 kDa 两种蛋白质的丝氨酸和苏氨酸残基在低渗条件下发生去磷酸化，但在高渗条件下仍保持磷酸化，表明这些蛋白质磷酸化不仅与高渗条件下的运动激活有关，而且对渗透压具有抵抗作用。 41 kDa 蛋白质的苏氨酸残基在干精子中也被磷酸化，甚至在运动可行的低渗条件下的 FWT 精子中也是如此。运动装置的适应可能与调节 Ca2+ 流量以增加 [Ca2+]i 和蛋白质磷酸化有关。
Euryhaline tilapia Oreochromis mossambicus can reproduce in freshwater and in seawater. Regulation of sperm motility appears to be modulated during acclimation of the fish from freshwater to seawater, being independent of extracellular Ca2+ in freshwater and dependent on extracellular Ca2+ in seawater. In the presence of extracellular Ca2+, sperm of seawater-acclimated tilapia (SWT) showed motility even in a hypertonic environment, whereas sperm of freshwater-acclimated tilapia (FWT) were not motile. The Ca2+ indicator, fluo-3, revealed that intracellular Ca2+ concentration, [Ca2+]i, of SWT sperm increased only in the presence of extracellular Ca2+ in hypotonic or hypertonic conditions. Since the increased [Ca2+]i in FWT sperm occurred under hypotonic conditions via intracellular Ca2+ stores, it is likely that tilapia modulate their source of increasing [Ca2+]i from intracellular stores (in FWT sperm) to extracellular stores (in SWT sperm). Experiments using demembranated sperm revealed that Ca2+ is necessary for activation of motility, suggesting that Ca2+ plays a key role in motility regulation in SWT sperm. We detected three phosphoproteins associated with the activation of sperm motility. Serine and threonine residues of two proteins of 15 kDa and 18 kDa became dephosphorylated in hypotonic conditions but remained phosphorylated in hypertonic conditions, suggesting that these protein phosphorylations were not only related to motility activation under hypertonic conditions but also resistant to osmotic pressure. The threonine residue(s) of a 41 kDa protein was also phosphorylated in dry sperm, even in FWT sperm in motility-feasible hypotonic conditions. It is likely that acclimation of the motility apparatus is associated with modulation of the flow of Ca2+ to increase [Ca2+]i and protein phosphorylation.