New possible roles for aquaporin-4 in astrocytes: cell cytoskeleton and functional relationship with connexin43
New possible roles for aquaporin-4 in astrocytes: cell cytoskeleton and functional relationship with connexin43
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DOI：
10.1096/fj.04-3281fje
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发表时间：
2005-08-01
期刊：
影响因子：
4.8
通讯作者：
Spray, DC
中科院分区：
文献类型：
--
作者：
Nicchia, GP;Srinivas, M;Spray, DC
水通道蛋白4（AQP4）是大脑中的主要水通道，在小鼠、大鼠和人类星形胶质细胞的血管周膜中表达。在先前的一项研究中，我们使用小干扰RNA（siRNA）特异性地敲低大鼠原代培养星形胶质细胞中的AQP4，发现除了渗透通透性降低外，AQP4敲低（KD）还导致细胞形态改变。然而，最近一份关于AQP4基因敲除小鼠（KO）原代培养星形胶质细胞的报告显示，与野生型相比没有形态差异。在这项研究中，我们比较了在小鼠、大鼠和人类原代培养星形胶质细胞中AQP4敲低的效果，发现人类星形胶质细胞中AQP4敲低导致的形态表型与在大鼠中发现的相似。相比之下，小鼠星形胶质细胞中AQP4敲低仅引起非常轻微的形态变化。未经处理的星形胶质细胞的肌动蛋白细胞骨架表现出强烈的物种特异性差异，F - 肌动蛋白在小鼠中呈皮质带状排列，在大鼠和人类星形胶质细胞中呈应力纤维状排列。令人惊讶的是，由于AQP4敲低，F - 肌动蛋白细胞骨架在大鼠和人类中解聚，而在小鼠星形胶质细胞中则完全重排。尽管AQP4敲低诱导了细胞骨架的改变，但我们发现抗肌萎缩蛋白（DP71）、β - 肌营养不良聚糖和α - syntrophin的表达没有改变。培养的小鼠星形胶质细胞中AQP4敲低使连接蛋白43（Cx43）强烈下调，同时细胞耦合减少，而在大鼠和人类细胞中未发现Cx43表达有重大改变。综上所述，这些结果表明，就这些特性而言，培养的人类星形胶质细胞与大鼠的比与小鼠的更相似。此外，尽管小鼠星形胶质细胞中AQP4敲低没有导致显著的形态表型，但它诱导了F - 肌动蛋白的显著重排，这与抗肌萎缩蛋白复合物的破坏无关，表明该水通道在观察到的细胞骨架变化中起主要作用。最后，AQP4敲低的小鼠星形胶质细胞中Cx43的强烈下调和细胞耦合表明，大脑星形胶质细胞中的水通道和间隙连接之间可能存在功能关系。
Aquaporin-4 (AQP4), the main water channel in the brain, is expressed in the perivascular membranes of mouse, rat, and human astrocytes. In a previous study, we used small interfering RNA (siRNA) to specifically knock down AQP4 in rat astrocyte primary cultures and found that together with reduced osmotic permeability, AQP4 knockdown (KD) led to altered cell morphology. However, a recent report on primary cultured astrocytes from AQP4 null mice (KO) showed no morphological differences compared with wild types. In this study, we compared the effect of AQP4 KD in mouse, rat, and human astrocyte primary cultures and found that AQP4 KD in human astrocytes resulted in a morphological phenotype similar to that found in rat. In contrast, AQP4 KD in mouse astrocytes caused only very mild morphological changes. The actin cytoskeleton of untreated astrocytes exhibited strong species-specific differences, with F-actin being organized in cortical bands in mouse and in stress fibers in rat and human astrocytes. Surprisingly, as a consequence of AQP4 KD, F-actin cytoskeleton was depolymerized in rat and human whereas it was completely rearranged in mouse astrocytes. Although AQP4 KD induced alterations of the cell cytoskeleton, we found that the expression of dystrophin (DP71), beta-dystroglycan, and alpha-syntrophin was not altered. AQP4 KD in cultured mouse astrocytes produced strong down-regulation of connexin43 (Cx43) with a concomitant reduction in cell coupling while no major alterations in Cx43 expression were found in rat and human cells. Taken together, these results demonstrate that with regard to these properties, human astrocytes in culture are more similar to rat than to mouse astrocytes. Moreover, even though AQP4 KD in mouse astrocytes did not result in a dramatic morphological phenotype, it induced a remarkable rearrangement of F-actin, not related to disruption of the dystrophin complex, indicating a primary role of this water channel in the cytoskeleton changes observed. Finally, the strong down-regulation of Cx43 and cell coupling in AQP4 KD mouse astrocytes indicate that a functional relationship likely exists between water channels and gap junctions in brain astrocytes.