Altered sensitivity of posttranslationally modified microtubules to methylmercury in differentiating embryonal carcinoma-derived neurons
Altered sensitivity of posttranslationally modified microtubules to methylmercury in differentiating embryonal carcinoma-derived neurons
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DOI：
10.1006/taap.1997.8138
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发表时间：
1997-06-01
影响因子：
3.8
通讯作者：
Reuhl, KR
中科院分区：
文献类型：
--
作者：
Graff, RD;Falconer, MM;Reuhl, KR
用免疫荧光显微镜观察了甲基汞（MeHg）对维甲酸诱导的胚胎癌（EC）细胞分化为神经元过程中微管（MTs）的影响。未分化的EC细胞主要含有从中心体延伸的动力学不稳定的酪氨酸化（TYR）MT和通常（但不限于）与中心体相关的稳定乙酰化（ACT）MT的小群体。未分化细胞的TYR MTs在暴露于低浓度的甲基汞（1-2 μ M）时经历了浓度和时间依赖性的分解，而ACT MTs在低浓度时对甲基汞具有抗性，即使在5 μ M的甲基汞中，许多仍保持完整。在视黄酸中2天后，短神经炎突起的出现指示早期分化。TYR MTs在短神经突和细胞索马中占主导地位，并对低浓度的甲基汞敏感。ACT MT也延伸到短的神经突中，但最常见的是在胞体内的小束中。ACT MT对甲基汞的抵抗力仍然高于TYR MT。在分化的第二天，首先检测到神经元特异性微管蛋白同种型β III。用抗体标记的结核分枝杆菌显示类似的敏感性甲基汞作为TYR结核分枝杆菌，这表明结核分枝杆菌含有β III主要是酪氨酸。分化4天和6天后，出现了更多的β III阳性神经元，神经突起逐渐变长并经常分支。TYR MT存在于细胞索马和神经突中，而ACT MT几乎仅存在于神经突中。与ACT MT相比，TYR MT在所有分化阶段对甲基汞仍然高度敏感（最明显的是在胞体中）;然而，随着培养时间的增加，即使TYR MT对甲基汞也获得了可观的稳定性。这些数据表明，微管在发展中的神经元越来越多的抵抗拆卸甲基汞，这表明MT的敏感性最关键的时期发生在非常早期的发展在体内。(C)1997年学术出版社。
The effects of methylmercury (MeHg) on microtubules (MTs) in differentiating neurons derived from retinoic acid-induced embryonal carcinoma (EC) cells in culture were examined by immunofluorescence microscopy. Undifferentiated EC cells contained mostly kinetically labile tyrosinated (TYR) MTs which extended from the centrosome and a small population of stable acetylated (ACT) MTs usually (but not exclusively) associated with the centrosome. TYR MTs of undifferentiated cells underwent concentration- and time-dependent disassembly upon exposure to low concentrations of MeHg (1-2 mu M), whereas ACT MTs were resistant to MeHg at low concentrations, with many remaining intact even in 5 mu M MeHg. After 2 days in retinoic acid the appearance of short neuritic processes was indicative of early differentiation. TYR MTs predominated both in the short neurites and cell soma and remained susceptible to low concentrations of MeHg. ACT MTs also extended into the short neurites but were most often found in small bundles within the perikarya. ACT MTs remained more resistant to MeHg than TYR MTs. The neuron-specific tubulin isotype beta III was first detected during the second day of differentiation. MTs labeled with antibodies to pm showed similar sensitivity to MeHg as TYR MTs, suggesting that MTs containing beta III were largely tyrosinated. After 4 and 6 days of differentiation a greater number of beta III-positive neurons were present with progressively longer and often branching neurites. TYR MTs were present in cell soma and neurites while ACT MTs were found almost exclusively in neurites. TYR MTs remained highly susceptible to MeHg (most notably in perikarya) in comparison to ACT MTs at all stages of differentiation; however, with increasing time in culture, even TYR MTs gained appreciable stability to MeHg. These data indicate that microtubules in developing neurons become progressively more resistant to disassembly by MeHg, suggesting that the most critical period of MT susceptibility occurs very early in development in vivo. (C) 1997 Academic Press.