Tubulin posttranslational modifications induced by cadmium in the sponge Clathrina clathrus

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• 作者：F.D. Ledda ; P. Ramoino ; S. Ravera ; E. Perino ; P. Bianchini ; A. Diaspro ; L. Gallus ; R. Pronzato ; R. Manconi
• 关键词：Cadmium ; Microtubule network ; Tubulin posttranslational modifications ; Porifera
• 刊名：Aquatic Toxicology
• 出版年：2013
• 出版时间：15 September, 2013
• 年：2013
• 卷：140-141
• 期：Complete
• 页码：98-105
• 全文大小：3056 K

文摘

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 ¦Á- and ¦Â-tubulin remained relatively constant in C. clathrus when exposed to 1 and 5 ¦ÌM CdCl₂, there were progressive shifts in the levels of some tubulin isoforms. Exposure for 24 h to sublethal concentrations of cadmium reduced the level of tyrosinated ¦Á-tubulin and enhanced the levels of acetylated and detyrosinated ¦Á-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 ¦Á-tubulin. By contrast, the reactivity with a monoclonal antibody that recognizes acetylated ¦Á-tubulin and with a polyclonal antibody specific for detyrosinated ¦Á-tubulin was enhanced at the same time points. Because the acetylation and detyrosination of ¦Á-tubulin occur on stable microtubules, the marked enhancement of ¦Á-tubulin acetylation and detyrosination in Cd²⁺-treated cells indicates that divalent Cd ions stabilize microtubules. The possibility that Cd²⁺ may increase the stability of cytoplasmic microtubules was tested by exposing Cd²⁺-treated cells to a cold temperature (0 ¡ãC). As shown, the microtubule bundles induced by Cd²⁺, which were labeled by the monoclonal antibodies against acetylated and detyrosinated ¦Á-tubulin, were resistant to cold.