De Camilli P, Miller P E, Navone F, Theurkauf W E, Vallee R B
Neuroscience. 1984 Apr;11(4):817-46.
It has recently been reported that high molecular weight microtubule-associated proteins are differently distributed in dendrites and axons of neurons [ Matus Bernhardt and Hugh-Jones (1981), Proc. natn Acad. Sci. U.S.A. 78, 3010-3014; Vallee (1982), J. Cell Biol. 92, 435-442]. We have reported earlier in a preliminary form [Miller, Walter, Theurkauf , Vallee and De Camilli (1982), Proc. natn Acad. Sci. U.S.A. 79, 5562-5566] that an antiserum specific for microtubule-associated protein 2, one of the most prominent high molecular weight microtubule-associated proteins in brain and a major brain phosphoprotein, stains specifically neuronal dendrites and perikarya. We have now extended those observations by performing a detailed analysis of the distribution of microtubule-associated protein 2 throughout the nervous system of the rat. We found that microtubule-associated protein 2 is present at high concentrations in the great majority of neurons. Under our conditions of immunostaining microtubule-associated protein 2 was not detected in nonneuronal cells. In all neurons it was compartmentalized in perikarya and dendrites. In most cases, the latter were more heavily stained than perikarya. The pattern of staining (overall intensity, relative intensity in dendrites vs perikarya, and in proximal vs distal segments of the dendritic tree), varied in different classes of neurons but was identical for all neurons with similar geometry in the same brain region. Different patterns of staining were found in dendritic trees with dissimilar branching characteristics. In all cases staining for microtubule-associated protein 2 in dendrites was consistent with a localization of microtubule-associated protein 2 on dendritic microtubules. Neuronal processes clearly identifiable as axons or axon terminals were not immunostained. Afferent processes of primary sensory cells were also unstained. Our findings indicate that microtubule-associated protein 2 is a component of the vast majority, and possibly all, neurons. It is highly concentrated in "bona fide" dendrites, i.e. in processes specialized for the reception of synaptic inputs on their surface and highly dependent on such inputs for their growth. The location of microtubule-associated protein 2, a major target for second messenger-regulated protein kinases, in these processes, supports the hypothesis that its phosphorylation might participate in the transduction of neurotransmitter signals in target nerve cells.
最近有报道称，高分子量微管相关蛋白在神经元的树突和轴突中分布不同[马图斯·伯恩哈特和休 - 琼斯（1981年），《美国国家科学院院刊》78卷，3010 - 3014页；瓦利（1982年），《细胞生物学杂志》92卷，435 - 442页]。我们之前曾以初步形式报道过[米勒、沃尔特、瑟考夫、瓦利和德·卡米利（1982年），《美国国家科学院院刊》79卷，5562 - 5566页]，一种针对微管相关蛋白2的抗血清，它是大脑中最突出的高分子量微管相关蛋白之一，也是一种主要的脑磷蛋白，能特异性地标记神经元的树突和胞体。我们现在通过对大鼠整个神经系统中微管相关蛋白2的分布进行详细分析，扩展了这些观察结果。我们发现微管相关蛋白2在绝大多数神经元中浓度很高。在我们的免疫染色条件下，未在非神经元细胞中检测到微管相关蛋白2。在所有神经元中，它都分布在胞体和树突中。在大多数情况下，树突的染色比胞体更浓。染色模式（总体强度、树突与胞体的相对强度以及树突树近端与远端节段的相对强度）在不同类型的神经元中有所不同，但在同一脑区具有相似几何形状的所有神经元中是相同的。在具有不同分支特征的树突树中发现了不同的染色模式。在所有情况下，树突中微管相关蛋白2的染色与微管相关蛋白2在树突微管上的定位一致。明显可识别为轴突或轴突终末的神经元突起未被免疫染色。初级感觉细胞的传入突起也未染色。我们的研究结果表明，微管相关蛋白2是绝大多数甚至可能是所有神经元的组成成分。它高度集中在“真正的”树突中，即在其表面专门用于接收突触输入且其生长高度依赖此类输入的突起中。微管相关蛋白2作为第二信使调节的蛋白激酶的主要作用靶点，在这些突起中的定位支持了这样一种假说，即其磷酸化可能参与靶神经细胞中神经递质信号的转导。
