Cholesterol-dependent modulation of dendrite outgrowth and microtubule stability in cultured neurons
Cholesterol-dependent modulation of dendrite outgrowth and microtubule stability in cultured neurons
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DOI：
10.1046/j.0022-3042.2001.00686.x
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发表时间：
2002-01-01
影响因子：
4.7
通讯作者：
Michikawa, M
中科院分区：
文献类型：
--
作者：
Fan, QW;Yu, W;Michikawa, M
微管相关蛋白2（Microtubule-associated protein 2，MAP 2）是一种神经元特异性的细胞骨架蛋白，主要分布于树突和细胞体中。MAP 2以磷酸化依赖的方式调节微管稳定性，这与树突生长和分支有关。我们以前报道过胆固醇缺乏会导致轴突中tau蛋白磷酸化和微管解聚（Fan et al.2001）。为了研究胆固醇是否也通过调节MAP 2磷酸化来调节树突中微管的稳定性，我们使用培养的神经元检测了3-羟基-3-甲基戊二酰辅酶A（HMG-CoA）还原酶抑制剂compactin和角鲨烯环氧酶抑制剂TU-2078（TU）对这些参数的影响。我们已经发现，胆固醇缺乏诱导的compactin和TU，抑制树突生长，但不是轴突，和衰减轴突分支。MAP 2的去磷酸化和微管解聚伴随着这些变化。与微管结合的蛋白磷酸酶2A（PP 2A）的量及其活性减少，而与微管结合的蛋白磷酸酶2A的量及其活性增加。合成的神经酰胺水平和总神经酰胺含量增加，这些胆固醇缺乏的神经元。这些变化所造成的compactin被阻止的同时处理的培养的神经元与β-迁移极低密度脂蛋白（β-VLDL）或胆固醇。两者合计，我们建议，胆固醇缺乏导致选择性抑制树突生长由于微管的稳定性降低，作为抑制MAP 2磷酸化的结果。
Microtubule-associated protein 2 (MAP2) is a neuron-specific cytoskeletal protein enriched in dendrites and cell bodies. MAP2 regulates microtubule stability in a phosphorylation-dependent manner, which has been implicated in dendrite outgrowth and branching. We have previously reported that cholesterol deficiency causes tau phosphorylation and microtubule depolymerization in axons (Fan et al. 2001). To investigate whether cholesterol also modulates microtubule stability in dendrites by modulating MAP2 phosphorylation, we examined the effect of compactin, a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, and TU-2078 (TU), a squalene epoxidase inhibitor, on these parameters using cultured neurons. We have found that cholesterol deficiency induced by compactin and TU, inhibited dendrite outgrowth, but not of axons, and attenuated axonal branching. Dephosphorylation of MAP2 and microtubule depolymerization accompanied these alterations. The amount of protein phosphatase 2 A (PP2A) and its activity in association with microtubules were decreased, while those unbound to microtubules were increased. The synthesized ceramide levels and the total ceramide content were increased in these cholesterol-deficient neurons. These alterations caused by compactin were prevented by concurrent treatment of cultured neurons with beta-migrating very-low-density lipoproteins (beta-VLDL) or cholesterol. Taken together, we propose that cholesterol-deficiency causes a selective inhibition of dendrite outgrowth due to the decreased stability of microtubules as a result of inhibition of MAP2 phosphorylation.