Herrero-González Sandra, Valle-Casuso José Carlos, Sánchez-Alvarez Rosa, Giaume Christian, Medina José M, Tabernero Arantxa
Departamento de Bioquímica y Biología Molecular, INCYL, Universidad de Salamanca, Spain.
Glia. 2009 Jan 15;57(2):222-33. doi: 10.1002/glia.20748.
In previous studies, we showed that endothelin-1 increased astrocyte proliferation and glucose uptake. These effects were similar to those observed with other gap junction inhibitors, such as carbenoxolone (CBX). Because 24-h treatment with endothelin-1 or CBX downregulates the expression of connexin43, the main protein forming astrocytic gap junctions, which can also be involved in proliferation, in this study, we addressed the possible role of connexin43 in the effects of endothelin-1. To do so, connexin43 was silenced in astrocytes by siRNA. The knock down of connexin43 increased the rate of glucose uptake, characterized by the upregulation of GLUT-1 and type I hexokinase. Neither endothelin-1 nor CBX were able to further increase the rate of glucose uptake in connexin43-silenced astrocytes. In agreement, no effects of endothelin-1 and CBX on GLUT-1 and type I hexokinase were observed in connexin-43 silenced astrocytes or in astrocytes from connexin43 knock-out (KO) mice. Our previous studies suggested a close relationship between glucose uptake and astrocyte proliferation. Consistent with this, connexin43-silenced astrocytes exhibited an increase in Ki-67, a marker of proliferation. The effects of ET-1 on retinoblastoma phosphorylation on Ser780 and on the upregulation of cyclins D1 and D3 were affected by the levels of connexin43. In conclusion, our results indicate that connexin43 participates in the effects of endothelin-1 on glucose uptake and proliferation in astrocytes. Interestingly, although the rate of growth in connexin43 KO astrocytes has been reported to be reduced, we observed that an acute reduction in connexin43 by siRNA increased proliferation and glucose uptake.
在先前的研究中，我们发现内皮素-1可增加星形胶质细胞的增殖和葡萄糖摄取。这些作用与其他缝隙连接抑制剂（如甘草次酸（CBX））所观察到的作用相似。由于用内皮素-1或CBX处理24小时会下调连接蛋白43的表达，连接蛋白43是形成星形胶质细胞缝隙连接的主要蛋白质，其也可能参与增殖，因此在本研究中，我们探讨了连接蛋白43在内皮素-1作用中的可能作用。为此，通过小干扰RNA（siRNA）使星形胶质细胞中的连接蛋白43沉默。连接蛋白43的敲低增加了葡萄糖摄取率，其特征是葡萄糖转运蛋白-1（GLUT-1）和I型己糖激酶的上调。在内皮素-1和CBX均不能进一步增加连接蛋白43沉默的星形胶质细胞中的葡萄糖摄取率。同样，在内皮素-1和CBX对连接蛋白43沉默的星形胶质细胞或连接蛋白43基因敲除（KO）小鼠的星形胶质细胞中的GLUT-1和I型己糖激酶均未观察到作用。我们先前的研究表明葡萄糖摄取与星形胶质细胞增殖之间存在密切关系。与此一致的是，连接蛋白43沉默的星形胶质细胞中增殖标志物Ki-67增加。内皮素-1对视网膜母细胞瘤Ser780位点磷酸化以及细胞周期蛋白D1和D3上调的作用受连接蛋白43水平的影响。总之，我们的结果表明连接蛋白43参与了内皮素-1对星形胶质细胞葡萄糖摄取和增殖的作用。有趣地是，尽管据报道连接蛋白43基因敲除的星形胶质细胞的生长速率降低，但我们观察到通过siRNA急性降低连接蛋白43会增加增殖和葡萄糖摄取。
