Ding A, Chen B, Fuortes M, Blum E
Beatrice and Samuel A. Seaver Laboratory, Department of Medicine, Cornell University Medical College, New York 10021, USA.
J Exp Med. 1996 Apr 1;183(4):1899-904. doi: 10.1084/jem.183.4.1899.
Taxol, a microtubule-binding diterpene, mimics many effects of lipopolysaccharide (LPS) on mouse macrophages. The LPS-mimetic effects of taxol appear to be under the same genetic control as responses to LPS itself. Thus we have postulated a role for microtubule-associated proteins (MAP) in the response of macrophages to LPS. Stimulation of macrophages by LPS quickly induces the activation of mitogen-activated protein kinases (MAPK). MAPK are generally considered cytosolic enzymes. Herein we report that much of the LPS-activatable pool of MAPK in primary mouse peritoneal macrophages is microtubule associated. By immunofluorescence, MAPK were localized to colchicine- and nocodazole-disruptible filaments. From both mouse brain and RAW 264.7 macrophages, MAPK could be coisolated with polymerized tubulin. Fractionation of primary macrophages into cytosol-, microfilament-, microtubule-, and intermediated filament-rich extracts revealed that approximately 10% of MAPK but none of MAPK kinase (MEK1A and MEK2) was microtubule bound. Exposure of macrophages to LPS did not change the proportion of MAPK bound to microtubules, but preferentially activated the microtubule-associated pool. These findings confirm the prediction that LPS activates a kinase bound to microtubules. Together with LPS-mimetic actions of taxol and the shared genetic control of responses to LPS and taxol, these results support the hypothesis that a major LPS-signaling pathway in mouse macrophages may involve activation of one or more microtubule-associated kinases.
紫杉醇是一种与微管结合的二萜类化合物，可模拟脂多糖（LPS）对小鼠巨噬细胞的多种作用。紫杉醇的LPS模拟作用似乎与对LPS本身的反应受相同的基因控制。因此，我们推测微管相关蛋白（MAP）在巨噬细胞对LPS的反应中起作用。LPS刺激巨噬细胞可迅速诱导丝裂原活化蛋白激酶（MAPK）的激活。MAPK通常被认为是胞质酶。在此我们报告，原代小鼠腹腔巨噬细胞中大部分可被LPS激活的MAPK与微管相关。通过免疫荧光，MAPK定位于秋水仙碱和诺考达唑可破坏的细丝上。从小鼠脑和RAW 264.7巨噬细胞中，MAPK均可与聚合的微管蛋白共分离。将原代巨噬细胞分离成富含胞质溶胶、微丝、微管和中间丝的提取物，结果显示约10%的MAPK与微管结合，而MAPK激酶（MEK1A和MEK2）均不与微管结合。巨噬细胞暴露于LPS并未改变与微管结合的MAPK比例，但优先激活了与微管相关的池。这些发现证实了LPS激活与微管结合的激酶这一预测。连同紫杉醇的LPS模拟作用以及对LPS和紫杉醇反应的共同基因控制，这些结果支持了这样一种假说，即小鼠巨噬细胞中主要的LPS信号通路可能涉及一种或多种与微管相关的激酶的激活。
