Kobayashi T, Storrie B, Simons K, Dotti C G
Cell Biology Program, European Molecular Biology Laboratory, Heidelberg, Germany.
Nature. 1992 Oct 15;359(6396):647-50. doi: 10.1038/359647a0.
In polarized neurons, axons and dendrites perform different functions, which are reflected in their different molecular organization. Studies on the sorting of viral and endogenous glycoproteins in epithelial cells and hippocampal neurons suggest that there may be similarities in the mechanism of sorting in these two cell types. The mechanisms that maintain the distinct composition of the two plasma membrane domains in these two cell types must, however, be different. We have proposed the existence of a functional barrier at the axonal hillock/initial segment which prevents the intermixing of membrane constituents. Here we test this hypothesis by fusing liposomes containing fluorescent phospholipids into the plasma membrane of polarized hippocampal cells in culture. Fusion was induced by lowering the pH and mediated by influenza virus haemagglutinin expressed on the axonal surface of neurons infected with fowl plague virus. Labelling was found exclusively on axons after fusion. Although the fused lipids were mobile on the axonal membrane, no labelling was detected on the cell body and dendritic surfaces. These results suggest that there is a diffusion barrier at the axonal hillock/initial segment which maintains the compositional differences between the axonal and somatodendritic domains.
在极化神经元中，轴突和树突执行不同的功能，这反映在它们不同的分子组织上。对上皮细胞和海马神经元中病毒及内源性糖蛋白分选的研究表明，这两种细胞类型的分选机制可能存在相似性。然而，维持这两种细胞类型中两个质膜结构域独特组成的机制必定不同。我们提出在轴丘/起始段存在功能屏障，可防止膜成分相互混合。在此，我们通过将含有荧光磷脂的脂质体融合到培养的极化海马细胞的质膜中来检验这一假设。融合是通过降低pH值诱导的，并由感染鸡瘟病毒的神经元轴突表面表达的流感病毒血凝素介导。融合后仅在轴突上发现标记。尽管融合的脂质在轴突膜上可移动，但在细胞体和树突表面未检测到标记。这些结果表明，在轴丘/起始段存在扩散屏障，可维持轴突和胞体树突结构域之间的成分差异。
