O'Brien E T, Asai D J, Jacobs R S, Wilson L
Department of Biological Sciences, University of California, Santa Barbara 93106.
Mol Pharmacol. 1989 May;35(5):635-42.
Stypoldione is a marine natural product that inhibits cells division in marine embryos and in mammalian cell cultures. The mechanism responsible for the ability of the compound to inhibit cell division is not known. The compound was found in early studies to inhibit polymerization of tubulin into microtubules in vitro, which lead to the suggestion that inhibition of microtubule polymerization in cells might be responsible for the ability of the compound to inhibit cell division. More recently, stypoldione was found to react covalently with the sulfhydryl groups of a number of proteins including tubulin and with sulfhydryl groups of peptides and small molecules. Thus, stypoldione could potentially react with a large number of cellular targets. In the present study, we have examined the effects of stypoldione on the organization of microtubules and chromatin in cells, in relation to the ability of the compound to inhibit cell division. We used indirect immunofluorescence light microscopy of fixed and stained sea urchin embryos during the first and second divisions after fertilization, with stains specific for tubulin and DNA. We found that stypoldione exerted qualitatively different effects on cell division and microtubule organization and function at different concentrations. At the lowest effective concentrations, 5-10 microM, stypoldione selectively inhibited cytokinesis. Mitotic division occurred normally, usually with no discernible perturbation of microtubule organization or function, and cells became multinuclear. At somewhat higher concentrations, 20-40 microM, stypoldione blocked embryos before streak stage of the first division and, although microtubules were present, their organization was perturbed and they often formed unusual "spiral aster" arrays. At 80 microM and above, microtubules in blocked cells were largely absent. Thus, stypoldione uncouples cytokinesis from mitosis at the lowest effective concentrations and, although it can disrupt microtubules at relatively higher concentrations, it inhibits cell division at the lowest effective concentrations by a selective action on cytokinesis through a mechanism that does not appear to involve disassembly of microtubules.
斯替波地酮是一种海洋天然产物，它能抑制海洋胚胎和哺乳动物细胞培养中的细胞分裂。该化合物抑制细胞分裂能力的机制尚不清楚。在早期研究中发现，该化合物在体外能抑制微管蛋白聚合成微管，这表明细胞中微管聚合的抑制可能是该化合物抑制细胞分裂能力的原因。最近，发现斯替波地酮能与包括微管蛋白在内的多种蛋白质的巯基以及肽和小分子的巯基发生共价反应。因此，斯替波地酮可能会与大量细胞靶点发生反应。在本研究中，我们研究了斯替波地酮对细胞中微管和染色质组织的影响，以及该化合物抑制细胞分裂的能力。我们在受精后的第一次和第二次分裂期间，对固定和染色的海胆胚胎进行间接免疫荧光显微镜检查，使用针对微管蛋白和DNA的特异性染色剂。我们发现，斯替波地酮在不同浓度下对细胞分裂以及微管组织和功能产生了性质不同的影响。在最低有效浓度5 - 10微摩尔时，斯替波地酮选择性地抑制胞质分裂。有丝分裂正常发生，通常微管组织或功能没有明显扰动，细胞变成多核。在稍高浓度20 - 40微摩尔时，斯替波地酮在第一次分裂的条纹期之前阻断胚胎，尽管存在微管，但其组织受到扰动，它们经常形成不寻常的“螺旋星状体”阵列。在80微摩尔及以上时，被阻断细胞中的微管基本不存在。因此，斯替波地酮在最低有效浓度下使胞质分裂与有丝分裂解偶联，尽管它在相对较高浓度下能破坏微管，但它在最低有效浓度下通过对胞质分裂的选择性作用抑制细胞分裂，其机制似乎不涉及微管的解聚。
