Department of Environmental Chemistry, IDAEA-CSIC, Jordi Girona 18, 08034 Barcelona, Spain.
Aquat Toxicol. 2012 Oct 15;122-123:144-52. doi: 10.1016/j.aquatox.2012.06.008. Epub 2012 Jun 28.
Multixenobiotic resistance (MXR) of aquatic invertebrates has so far been associated with cellular efflux activity mediated by P-glycoprotein (ABCB1) and MRP (multidrug resistance protein; ABCC) type ABC (ATP binding cassette) transporters. Expression and activity of an abcb1/Abcb1 homolog has been shown in eggs and larvae of the zebra mussel Dreissena polymorpha. Here we report identification of a partial cDNA sequence of an abcc/Abcc homolog from zebra mussel that is transcribed and active as a cellular efflux transporter in embryos and gill tissue of adult mussels. Transcript expression levels were comparatively low in eggs and sharply increased after fertilization, then maintaining high expression levels in 1 and 2 dpf (days post fertilization) larvae. MK571, a known inhibitor of mammalian ABCC transporters, blocks efflux of calcein-am in larvae and gill tissue as indicated by elevated calcein fluorescence; this indicates the presence of active Abcc protein in cells of the larvae and gills. Dacthal and mercury used as chemical stressors both induced expression of abcb1 and abcc mRNAs in larvae; accordingly, assays with calcein-am and ABCB1 inhibitor reversin 205 and ABCC inhibitor MK571 indicated enhanced Abcb1 and Abcc efflux activities. Responses to chemicals were different in gills, where abcb1 transcript abundances were enhanced in dacthal and mercury treatments, whereas abcc mRNA was only increased with mercury. Abcb1 and Abcc activities did not in all cases show increases that were according to respective mRNA levels; thus, Abcc activity was significantly higher with dacthal, whereas Abcb1 activity was unchanged with mercury. Our data indicate that abcb1/Abcb1 and abcc/Abcc transporters are expressed and active in larvae and adult stages of zebra mussel. Expression of both genes is induced as cellular stress response, but regulation appears to differ in larvae and tissue of adult stages.
水生无脊椎动物的多药耐药性 (MXR) 迄今为止与 P 糖蛋白 (ABCB1) 和 MRP（多药耐药蛋白；ABCC）型 ABC（ATP 结合盒）转运体介导的细胞外排活性有关。斑马贻贝 Dreissena polymorpha 的卵和幼虫中已显示出 abcb1/Abcb1 同源物的表达和活性。在这里，我们报道了从斑马贻贝中鉴定出的 abcc/Abcc 同源物的部分 cDNA 序列，该序列在成贻贝的胚胎和鳃组织中作为细胞外排转运体转录并具有活性。在卵中，转录表达水平较低，受精后急剧增加，然后在 1 天和 2 天的幼虫（受精后天数）中保持高水平表达。MK571 是一种已知的哺乳动物 ABCC 转运体抑制剂，可阻止 calcein-am 在幼虫和鳃组织中的外排，这表明幼虫和鳃细胞中存在活跃的 Abcc 蛋白。用作化学应激物的敌草隆和汞都诱导了幼虫中 abcb1 和 abcc mRNA 的表达；因此，用 calcein-am 和 ABCB1 抑制剂 reversin 205 和 ABCC 抑制剂 MK571 进行的测定表明，Abcb1 和 Abcc 外排活性增强。在鳃中，化学物质的反应不同，敌草隆和汞处理中 abcb1 转录物丰度增加，而仅在汞处理中 abcc mRNA 增加。并非所有情况下，Abcb1 和 Abcc 活性的增加都与各自的 mRNA 水平相符；因此，敌草隆处理时 Abcc 活性显着更高，而汞处理时 Abcb1 活性不变。我们的数据表明，abcb1/Abcb1 和 abcc/Abcc 转运体在斑马贻贝的幼虫和成虫阶段表达并具有活性。两种基因的表达均作为细胞应激反应诱导，但在幼虫和成虫组织中的调节似乎不同。
