Dipartimento di Scienze della Terra, dell'Ambiente e della Vita (DISTAV), Università di Genova, Corso Europa 26, I-16132 Genova, Italy.
Aquat Toxicol. 2013 Sep 15;140-141:98-105. doi: 10.1016/j.aquatox.2013.05.013. Epub 2013 May 21.
As sessile filter feeders, sponges are exposed to environmental stress due to pollutants of both anthropogenic and natural origins and are able to accumulate harmful substances. Thus, sponges are considered a good tool for the biomonitoring of coastal areas. In this study, we used biochemical and immunocytochemical analyses to provide new data on the cadmium-related changes in sponge cells. In particular, we analyzed the effects of different concentrations of cadmium on the microtubule network in the calcisponge Clathrina clathrus. Quantitative densitometry of the immunoblots showed that, while the levels of α- and β-tubulin remained relatively constant in C. clathrus when exposed to 1 and 5 μM CdCl2, there were progressive shifts in the levels of some tubulin isoforms. Exposure for 24h to sublethal concentrations of cadmium reduced the level of tyrosinated α-tubulin and enhanced the levels of acetylated and detyrosinated α-tubulin relative to the levels in controls. Confocal microscopy analysis of immunolabeled tissue sections showed that the inhibitory effect of cadmium was associated with a decrease in the labeling of the cells with a monoclonal antibody that recognizes tyrosinated α-tubulin. By contrast, the reactivity with a monoclonal antibody that recognizes acetylated α-tubulin and with a polyclonal antibody specific for detyrosinated α-tubulin was enhanced at the same time points. Because the acetylation and detyrosination of α-tubulin occur on stable microtubules, the marked enhancement of α-tubulin acetylation and detyrosination in Cd(2+)-treated cells indicates that divalent Cd ions stabilize microtubules. The possibility that Cd(2+) may increase the stability of cytoplasmic microtubules was tested by exposing Cd(2+)-treated cells to a cold temperature (0°C). As shown, the microtubule bundles induced by Cd(2+), which were labeled by the monoclonal antibodies against acetylated and detyrosinated α-tubulin, were resistant to cold.
作为固着滤食动物，海绵由于人为和自然来源的污染物而暴露于环境压力之下，并且能够积累有害物质。因此，海绵被认为是沿海地区生物监测的良好工具。在这项研究中，我们使用生化和免疫细胞化学分析为海绵细胞与镉相关的变化提供了新的数据。特别是，我们分析了不同浓度的镉对钙海绵 Clathrina clathrus 微管网络的影响。免疫印迹的定量密度分析表明，当暴露于 1 和 5 μM CdCl2 时，α-和β-微管蛋白的水平在 C. clathrus 中相对保持不变，但某些微管蛋白同工型的水平发生了渐进性变化。暴露于亚致死浓度的镉 24 小时会降低酪氨酸化α-微管蛋白的水平，并增强乙酰化和去酪氨酸化α-微管蛋白的水平，与对照组相比。免疫组织化学分析显示，镉的抑制作用与识别酪氨酸化α-微管蛋白的单克隆抗体标记细胞的减少有关。相比之下，同时增强了与识别乙酰化α-微管蛋白的单克隆抗体和特异性识别去酪氨酸化α-微管蛋白的多克隆抗体的反应性。由于α-微管蛋白的乙酰化和去酪氨酸化发生在稳定的微管上，因此在 Cd2+处理的细胞中α-微管蛋白乙酰化和去酪氨酸化的明显增强表明二价 Cd 离子稳定了微管。通过将 Cd2+处理的细胞暴露于低温（0°C）来测试 Cd2+是否可能增加细胞质微管的稳定性。结果表明，Cd2+诱导的微管束，被针对乙酰化和去酪氨酸化α-微管蛋白的单克隆抗体标记，对低温具有抗性。
