King K L, Essig J, Roberts T M, Moerland T S
Department of Biological Science, Florida State University, Tallahassee 32306.
Cell Motil Cytoskeleton. 1994;27(3):193-205. doi: 10.1002/cm.970270302.
The development and locomotion of the amoeboid sperm of the nematode, Ascaris suum, depend on precise control of the assembly of their unique major sperm protein (MSP) filament system. We used fluorescence ratio imaging of cells loaded with BCECF to show that intracellular pH (pHi) is involved in controlling MSP polymerization in vivo. Spermatogenesis is marked by a cycle of MSP assembly-disassembly-reassembly that coincides with changes in pHi. In spermatocytes, which contain MSP in paracrystalline fibrous bodies, pHi was 6.8, 0.6 units higher than in spermatids, which disassemble the fibrous bodies and contain no assemblies of MSP filaments. Activation of spermatids to complete development resulted in rapid increase in pHi to 6.4 and reappearance of filaments. Treatment of spermatocytes with weak acids caused the fibrous bodies to disassemble whereas incubation of spermatids in weak bases induced MSP assembly. The MSP filaments in spermatozoa are organized into fiber complexes that flow continuously rearward from the leading edge of the pseudopod. These cells established a pseudopodial pH gradient with pHi 0.15 units higher at the leading edge, where fiber complexes assemble, than at the base of the pseudopod, where disassembly occurs. Acidification of these cells caused the MSP cytoskeleton to disassemble and abolished the pH gradient. Acid removal resulted in reassembly of the cytoskeleton, re-establishment of the pH gradient, and re-initiation of motility. MSP assembly in sperm undergoing normal development and motility and in cells responding to chemical manipulation of pHi occurs preferentially at membranes. Thus, we propose that filament assembly in sperm is controlled by pH-sensitive MSP-membrane interaction.
猪蛔虫线虫的阿米巴样精子的发育和运动，依赖于对其独特的主要精子蛋白（MSP）丝系统组装的精确控制。我们使用装载了BCECF的细胞进行荧光比率成像，以表明细胞内pH值（pHi）参与体内MSP聚合的控制。精子发生的特点是MSP组装 - 拆卸 - 重新组装的循环，这与pHi的变化相吻合。在含有副晶纤维体中MSP的精母细胞中，pHi为6.8，比精细胞中的pHi高0.6个单位，精细胞会分解纤维体且不含有MSP丝的组装。精细胞激活以完成发育导致pHi迅速升高至6.4并重新出现丝。用弱酸处理精母细胞会导致纤维体分解，而将精细胞在弱碱中孵育会诱导MSP组装。精子中的MSP丝组织成纤维复合体，从伪足的前缘持续向后流动。这些细胞建立了一个伪足pH梯度，在伪足前缘（纤维复合体组装的地方）的pHi比伪足基部（发生分解的地方）高0.15个单位。这些细胞的酸化导致MSP细胞骨架分解并消除了pH梯度。去除酸导致细胞骨架重新组装、pH梯度重新建立以及运动重新开始。在经历正常发育和运动的精子以及对pHi进行化学操作作出反应的细胞中，MSP组装优先发生在膜上。因此，我们提出精子中的丝组装是由pH敏感的MSP - 膜相互作用控制的。
